Add Gradle Kotlin DSL support

This commit refactors the existing Groovy DSL writers in order to share
code between the Groovy DSL and Kotlin DSL writers.

See gh-851

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/build/BuildProjectGenerationConfiguration.java

@@ -19,6 +19,7 @@ package io.spring.initializr.generator.spring.build;
 import io.spring.initializr.generator.buildsystem.Build;
 import io.spring.initializr.generator.buildsystem.DependencyScope;
 import io.spring.initializr.generator.buildsystem.gradle.GradleBuildSystem;
+import io.spring.initializr.generator.buildsystem.gradle.GradleKtsBuildSystem;
 import io.spring.initializr.generator.buildsystem.maven.MavenBuildSystem;
 import io.spring.initializr.generator.condition.ConditionalOnBuildSystem;
 import io.spring.initializr.generator.condition.ConditionalOnLanguage;
@@ -39,6 +40,7 @@ import org.springframework.context.annotation.Bean;
  * Project generation configuration for projects using any build system.
  *
  * @author Andy Wilkinson
+ * @author Jean-Baptiste Nizet
  */
 @ProjectGenerationConfiguration
 public class BuildProjectGenerationConfiguration {
@@ -70,7 +72,7 @@ public class BuildProjectGenerationConfiguration {
 
 	@Bean
 	@ConditionalOnLanguage(KotlinLanguage.ID)
-	@ConditionalOnBuildSystem(GradleBuildSystem.ID)
+	@ConditionalOnBuildSystem({ GradleBuildSystem.ID, GradleKtsBuildSystem.ID })
 	public KotlinJpaGradleBuildCustomizer kotlinJpaGradleBuildCustomizer(
 			InitializrMetadata metadata, KotlinProjectSettings settings) {
 		return new KotlinJpaGradleBuildCustomizer(metadata, settings);

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/build/gradle/GradleBuildProjectContributor.java

@@ -29,11 +29,14 @@ import io.spring.initializr.generator.io.IndentingWriterFactory;
 import io.spring.initializr.generator.project.contributor.ProjectContributor;
 
 /**
- * {@link ProjectContributor} for the project's {@code build.gradle} file.
+ * {@link ProjectContributor} template for the project's {@code build.gradle} or
+ * {@code build.gradle.kts} file. A subclass exists for each DSL.
  *
  * @author Andy Wilkinson
+ * @author Jean-Baptiste Nizet
  */
-public class GradleBuildProjectContributor implements BuildWriter, ProjectContributor {
+public abstract class GradleBuildProjectContributor
+		implements BuildWriter, ProjectContributor {
 
 	private final GradleBuildWriter buildWriter;
 
@@ -41,21 +44,25 @@ public class GradleBuildProjectContributor implements BuildWriter, ProjectContri
 
 	private final IndentingWriterFactory indentingWriterFactory;
 
-	GradleBuildProjectContributor(GradleBuildWriter buildWriter, GradleBuild build,
-			IndentingWriterFactory indentingWriterFactory) {
+	private final String buildFileName;
+
+	protected GradleBuildProjectContributor(GradleBuildWriter buildWriter,
+			GradleBuild build, IndentingWriterFactory indentingWriterFactory,
+			String buildFileName) {
 		this.buildWriter = buildWriter;
 		this.build = build;
 		this.indentingWriterFactory = indentingWriterFactory;
+		this.buildFileName = buildFileName;
 	}
 
 	@Override
-	public void contribute(Path projectRoot) throws IOException {
-		Path buildGradle = Files.createFile(projectRoot.resolve("build.gradle"));
+	public final void contribute(Path projectRoot) throws IOException {
+		Path buildGradle = Files.createFile(projectRoot.resolve(this.buildFileName));
 		writeBuild(Files.newBufferedWriter(buildGradle));
 	}
 
 	@Override
-	public void writeBuild(Writer out) throws IOException {
+	public final void writeBuild(Writer out) throws IOException {
 		try (IndentingWriter writer = this.indentingWriterFactory
 				.createIndentingWriter("gradle", out)) {
 			this.buildWriter.writeTo(writer, this.build);

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/build/gradle/GradleProjectGenerationConfiguration.java

@@ -23,7 +23,9 @@ import io.spring.initializr.generator.buildsystem.BuildItemResolver;
 import io.spring.initializr.generator.buildsystem.gradle.Gradle3BuildWriter;
 import io.spring.initializr.generator.buildsystem.gradle.GradleBuild;
 import io.spring.initializr.generator.buildsystem.gradle.GradleBuildSystem;
-import io.spring.initializr.generator.buildsystem.gradle.GradleBuildWriter;
+import io.spring.initializr.generator.buildsystem.gradle.GradleKtsBuildSystem;
+import io.spring.initializr.generator.buildsystem.gradle.GroovyDslGradleBuildWriter;
+import io.spring.initializr.generator.buildsystem.gradle.KotlinDslGradleBuildWriter;
 import io.spring.initializr.generator.condition.ConditionalOnBuildSystem;
 import io.spring.initializr.generator.condition.ConditionalOnLanguage;
 import io.spring.initializr.generator.condition.ConditionalOnPackaging;
@@ -35,6 +37,7 @@ import io.spring.initializr.generator.project.ProjectGenerationConfiguration;
 import io.spring.initializr.generator.project.ResolvedProjectDescription;
 import io.spring.initializr.generator.spring.build.BuildCustomizer;
 import io.spring.initializr.generator.spring.util.LambdaSafe;
+import io.spring.initializr.metadata.InitializrMetadata;
 
 import org.springframework.beans.factory.ObjectProvider;
 import org.springframework.context.annotation.Bean;
@@ -45,9 +48,10 @@ import org.springframework.context.annotation.Configuration;
  * Gradle as its build system.
  *
  * @author Andy Wilkinson
+ * @author Jean-Baptiste Nizet
  */
 @ProjectGenerationConfiguration
-@ConditionalOnBuildSystem(GradleBuildSystem.ID)
+@ConditionalOnBuildSystem({ GradleBuildSystem.ID, GradleKtsBuildSystem.ID })
 public class GradleProjectGenerationConfiguration {
 
 	private final IndentingWriterFactory indentingWriterFactory;
@@ -100,14 +104,24 @@ public class GradleProjectGenerationConfiguration {
 
 	@Bean
 	@ConditionalOnPlatformVersion("2.0.0.M1")
+	@ConditionalOnBuildSystem(GradleBuildSystem.ID)
 	public BuildCustomizer<GradleBuild> applyDependencyManagementPluginContributor() {
 		return (build) -> build.applyPlugin("io.spring.dependency-management");
 	}
 
 	@Bean
+	@ConditionalOnBuildSystem(GradleBuildSystem.ID)
 	public GradleBuildProjectContributor gradleBuildProjectContributor(
-			GradleBuildWriter buildWriter, GradleBuild build) {
-		return new GradleBuildProjectContributor(buildWriter, build,
+			GroovyDslGradleBuildWriter buildWriter, GradleBuild build) {
+		return new GroovyDslGradleBuildProjectContributor(buildWriter, build,
+				this.indentingWriterFactory);
+	}
+
+	@Bean
+	@ConditionalOnBuildSystem(GradleKtsBuildSystem.ID)
+	public KotlinDslGradleBuildProjectContributor gradleKtsBuildProjectContributor(
+			KotlinDslGradleBuildWriter buildWriter, GradleBuild build) {
+		return new KotlinDslGradleBuildProjectContributor(buildWriter, build,
 				this.indentingWriterFactory);
 	}
 
@@ -116,6 +130,7 @@ public class GradleProjectGenerationConfiguration {
 	 */
 	@Configuration
 	@ConditionalOnGradleVersion("3")
+	@ConditionalOnBuildSystem(GradleBuildSystem.ID)
 	static class Gradle3ProjectGenerationConfiguration {
 
 		@Bean
@@ -152,6 +167,7 @@ public class GradleProjectGenerationConfiguration {
 	 */
 	@Configuration
 	@ConditionalOnGradleVersion("4")
+	@ConditionalOnBuildSystem(GradleBuildSystem.ID)
 	static class Gradle4ProjectGenerationConfiguration {
 
 		@Bean
@@ -176,21 +192,23 @@ public class GradleProjectGenerationConfiguration {
 	}
 
 	/**
-	 * Configuration specific to projects using Gradle 4 or 5.
+	 * Configuration specific to projects using Gradle (Groovy DSL) 4 or 5.
 	 */
 	@Configuration
+	@ConditionalOnBuildSystem(GradleBuildSystem.ID)
 	@ConditionalOnGradleVersion({ "4", "5" })
 	static class Gradle4Or5ProjectGenerationConfiguration {
 
 		@Bean
-		public GradleBuildWriter gradleBuildWriter() {
-			return new GradleBuildWriter();
+		public GroovyDslGradleBuildWriter gradleBuildWriter() {
+			return new GroovyDslGradleBuildWriter();
 		}
 
 		@Bean
 		public SettingsGradleProjectContributor settingsGradleProjectContributor(
 				GradleBuild build, IndentingWriterFactory indentingWriterFactory) {
-			return new SettingsGradleProjectContributor(build, indentingWriterFactory);
+			return new GroovyDslSettingsGradleProjectContributor(build,
+					indentingWriterFactory);
 		}
 
 		@Bean
@@ -207,4 +225,38 @@ public class GradleProjectGenerationConfiguration {
 
 	}
 
+	/**
+	 * Configuration specific to projects using Gradle (Kotlin DSL).
+	 */
+	@Configuration
+	@ConditionalOnBuildSystem(GradleKtsBuildSystem.ID)
+	static class GradleKtsProjectGenerationConfiguration {
+
+		@Bean
+		public KotlinDslGradleBuildWriter gradleKtsBuildWriter() {
+			return new KotlinDslGradleBuildWriter();
+		}
+
+		@Bean
+		public KotlinDslSettingsGradleProjectContributor settingsGradleKtsProjectContributor(
+				GradleBuild build, IndentingWriterFactory indentingWriterFactory) {
+			return new KotlinDslSettingsGradleProjectContributor(build,
+					indentingWriterFactory);
+		}
+
+		@Bean
+		public BuildCustomizer<GradleBuild> springBootPluginContributor(
+				ResolvedProjectDescription projectDescription,
+				InitializrMetadata metadata) {
+			return (build) -> {
+				build.addPlugin("org.springframework.boot",
+						projectDescription.getPlatformVersion().toString());
+				build.addPlugin("io.spring.dependency-management",
+						metadata.getConfiguration().getEnv().getGradle()
+								.getDependencyManagementPluginVersion());
+			};
+		}
+
+	}
+
 }

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/build/gradle/GroovyDslGradleBuildProjectContributor.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2012-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.spring.initializr.generator.spring.build.gradle;
+
+import io.spring.initializr.generator.buildsystem.gradle.GradleBuild;
+import io.spring.initializr.generator.buildsystem.gradle.GroovyDslGradleBuildWriter;
+import io.spring.initializr.generator.io.IndentingWriterFactory;
+import io.spring.initializr.generator.project.contributor.ProjectContributor;
+
+/**
+ * {@link ProjectContributor} for the project's {@code build.gradle} file.
+ *
+ * @author Jean-Baptiste Nizet
+ */
+public class GroovyDslGradleBuildProjectContributor
+		extends GradleBuildProjectContributor {
+
+	GroovyDslGradleBuildProjectContributor(GroovyDslGradleBuildWriter buildWriter,
+			GradleBuild build, IndentingWriterFactory indentingWriterFactory) {
+		super(buildWriter, build, indentingWriterFactory, "build.gradle");
+	}
+
+}

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/build/gradle/GroovyDslSettingsGradleProjectContributor.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2012-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.spring.initializr.generator.spring.build.gradle;
+
+import io.spring.initializr.generator.buildsystem.gradle.GradleBuild;
+import io.spring.initializr.generator.buildsystem.gradle.GroovyDslGradleSettingsWriter;
+import io.spring.initializr.generator.io.IndentingWriterFactory;
+import io.spring.initializr.generator.project.contributor.ProjectContributor;
+
+/**
+ * {@link ProjectContributor} for the project's {@code settings.gradle} file.
+ *
+ * @author Jean-Baptiste Nizet
+ */
+class GroovyDslSettingsGradleProjectContributor extends SettingsGradleProjectContributor {
+
+	GroovyDslSettingsGradleProjectContributor(GradleBuild build,
+			IndentingWriterFactory indentingWriterFactory) {
+		super(build, indentingWriterFactory, new GroovyDslGradleSettingsWriter(),
+				"settings.gradle");
+	}
+
+}

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/build/gradle/KotlinDslGradleBuildProjectContributor.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2012-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.spring.initializr.generator.spring.build.gradle;
+
+import io.spring.initializr.generator.buildsystem.gradle.GradleBuild;
+import io.spring.initializr.generator.buildsystem.gradle.KotlinDslGradleBuildWriter;
+import io.spring.initializr.generator.io.IndentingWriterFactory;
+import io.spring.initializr.generator.project.contributor.ProjectContributor;
+
+/**
+ * {@link ProjectContributor} for the project's {@code build.gradle.kts} file.
+ *
+ * @author Jean-Baptiste Nizet
+ */
+public class KotlinDslGradleBuildProjectContributor
+		extends GradleBuildProjectContributor {
+
+	KotlinDslGradleBuildProjectContributor(KotlinDslGradleBuildWriter buildWriter,
+			GradleBuild build, IndentingWriterFactory indentingWriterFactory) {
+		super(buildWriter, build, indentingWriterFactory, "build.gradle.kts");
+	}
+
+}

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/build/gradle/KotlinDslSettingsGradleProjectContributor.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2012-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.spring.initializr.generator.spring.build.gradle;
+
+import io.spring.initializr.generator.buildsystem.gradle.GradleBuild;
+import io.spring.initializr.generator.buildsystem.gradle.KotlinDslGradleSettingsWriter;
+import io.spring.initializr.generator.io.IndentingWriterFactory;
+import io.spring.initializr.generator.project.contributor.ProjectContributor;
+
+/**
+ * {@link ProjectContributor} for the project's {@code settings.gradle.kts} file.
+ *
+ * @author Jean-Baptiste Nizet
+ */
+class KotlinDslSettingsGradleProjectContributor extends SettingsGradleProjectContributor {
+
+	KotlinDslSettingsGradleProjectContributor(GradleBuild build,
+			IndentingWriterFactory indentingWriterFactory) {
+		super(build, indentingWriterFactory, new KotlinDslGradleSettingsWriter(),
+				"settings.gradle.kts");
+	}
+
+}

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/build/gradle/SettingsGradleProjectContributor.java

@@ -27,11 +27,13 @@ import io.spring.initializr.generator.io.IndentingWriterFactory;
 import io.spring.initializr.generator.project.contributor.ProjectContributor;
 
 /**
- * {@link ProjectContributor} for the project's {@code settings.gradle} file.
+ * {@link ProjectContributor} for the project's {@code settings.gradle}
+ * {@code settings.gradle.kts} or file. A subclass exists for each of the DSLs.
  *
  * @author Andy Wilkinson
+ * @author Jean-Baptiste Nizet
  */
-class SettingsGradleProjectContributor implements ProjectContributor {
+abstract class SettingsGradleProjectContributor implements ProjectContributor {
 
 	private final GradleBuild build;
 
@@ -39,16 +41,21 @@ class SettingsGradleProjectContributor implements ProjectContributor {
 
 	private final GradleSettingsWriter settingsWriter;
 
-	SettingsGradleProjectContributor(GradleBuild build,
-			IndentingWriterFactory indentingWriterFactory) {
+	private final String settingsFileName;
+
+	protected SettingsGradleProjectContributor(GradleBuild build,
+			IndentingWriterFactory indentingWriterFactory,
+			GradleSettingsWriter settingsWriter, String settingsFileName) {
 		this.build = build;
 		this.indentingWriterFactory = indentingWriterFactory;
-		this.settingsWriter = new GradleSettingsWriter();
+		this.settingsWriter = settingsWriter;
+		this.settingsFileName = settingsFileName;
 	}
 
 	@Override
-	public void contribute(Path projectRoot) throws IOException {
-		Path settingsGradle = Files.createFile(projectRoot.resolve("settings.gradle"));
+	public final void contribute(Path projectRoot) throws IOException {
+		Path settingsGradle = Files
+				.createFile(projectRoot.resolve(this.settingsFileName));
 		try (IndentingWriter writer = this.indentingWriterFactory.createIndentingWriter(
 				"gradle", Files.newBufferedWriter(settingsGradle))) {
 			this.settingsWriter.writeTo(writer, this.build);

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/code/groovy/GroovyProjectGenerationDefaultContributorsConfiguration.java

@@ -20,6 +20,7 @@ import java.lang.reflect.Modifier;
 
 import io.spring.initializr.generator.buildsystem.Build;
 import io.spring.initializr.generator.buildsystem.gradle.GradleBuildSystem;
+import io.spring.initializr.generator.buildsystem.gradle.GradleKtsBuildSystem;
 import io.spring.initializr.generator.buildsystem.maven.MavenBuildSystem;
 import io.spring.initializr.generator.condition.ConditionalOnBuildSystem;
 import io.spring.initializr.generator.condition.ConditionalOnPackaging;
@@ -44,6 +45,7 @@ import org.springframework.context.annotation.Configuration;
  * Default Groovy language contributors.
  *
  * @author Stephane Nicoll
+ * @author Jean-Baptiste Nizet
  */
 @Configuration
 class GroovyProjectGenerationDefaultContributorsConfiguration {
@@ -121,7 +123,7 @@ class GroovyProjectGenerationDefaultContributorsConfiguration {
 	 * Configuration for Groovy projects built with Gradle.
 	 */
 	@Configuration
-	@ConditionalOnBuildSystem(GradleBuildSystem.ID)
+	@ConditionalOnBuildSystem({ GradleBuildSystem.ID, GradleKtsBuildSystem.ID })
 	static class GroovyGradleProjectConfiguration {
 
 		@Bean

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/code/kotlin/GroovyDslKotlinGradleBuildCustomizer.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2012-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.spring.initializr.generator.spring.code.kotlin;
+
+import java.util.stream.Collectors;
+
+import io.spring.initializr.generator.buildsystem.gradle.GradleBuild.TaskCustomization;
+import io.spring.initializr.generator.spring.build.BuildCustomizer;
+
+/**
+ * {@link BuildCustomizer} for Kotlin projects build with Gradle (Groovy DSL).
+ *
+ * @author Jean-Baptiste Nizet
+ */
+class GroovyDslKotlinGradleBuildCustomizer extends KotlinGradleBuildCustomizer {
+
+	GroovyDslKotlinGradleBuildCustomizer(KotlinProjectSettings kotlinProjectSettings) {
+		super(kotlinProjectSettings);
+	}
+
+	@Override
+	protected void customizeKotlinOptions(TaskCustomization compile) {
+		compile.nested("kotlinOptions", (kotlinOptions) -> {
+			String compilerArgs = this.settings.getCompilerArgs().stream()
+					.map((arg) -> "'" + arg + "'").collect(Collectors.joining(", "));
+			kotlinOptions.set("freeCompilerArgs", "[" + compilerArgs + "]");
+			kotlinOptions.set("jvmTarget", "'" + this.settings.getJvmTarget() + "'");
+		});
+	}
+
+}

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/code/kotlin/KotlinDslKotlinGradleBuildCustomizer.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2012-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.spring.initializr.generator.spring.code.kotlin;
+
+import java.util.stream.Collectors;
+
+import io.spring.initializr.generator.buildsystem.gradle.GradleBuild.TaskCustomization;
+import io.spring.initializr.generator.spring.build.BuildCustomizer;
+
+/**
+ * {@link BuildCustomizer} for Kotlin projects build with Gradle (Kotlin DSL).
+ *
+ * @author Jean-Baptiste Nizet
+ */
+class KotlinDslKotlinGradleBuildCustomizer extends KotlinGradleBuildCustomizer {
+
+	KotlinDslKotlinGradleBuildCustomizer(KotlinProjectSettings kotlinProjectSettings) {
+		super(kotlinProjectSettings);
+	}
+
+	@Override
+	protected void customizeKotlinOptions(TaskCustomization compile) {
+		compile.nested("kotlinOptions", (kotlinOptions) -> {
+			String compilerArgs = this.settings.getCompilerArgs().stream()
+					.map((arg) -> "\"" + arg + "\"").collect(Collectors.joining(", "));
+			kotlinOptions.set("freeCompilerArgs", "listOf(" + compilerArgs + ")");
+			kotlinOptions.set("jvmTarget", "\"" + this.settings.getJvmTarget() + "\"");
+		});
+	}
+
+}

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/code/kotlin/KotlinGradleBuildCustomizer.java

@@ -16,41 +16,33 @@
 
 package io.spring.initializr.generator.spring.code.kotlin;
 
-import java.util.stream.Collectors;
-
 import io.spring.initializr.generator.buildsystem.gradle.GradleBuild;
 import io.spring.initializr.generator.buildsystem.gradle.GradleBuild.TaskCustomization;
 import io.spring.initializr.generator.spring.build.BuildCustomizer;
 
 /**
- * {@link BuildCustomizer} for Kotlin projects build with Gradle.
+ * {@link BuildCustomizer} template for Kotlin projects build with Gradle. A subclass
+ * exists for each DSL.
  *
  * @author Andy Wilkinson
  * @author Jean-Baptiste Nizet
  */
-class KotlinGradleBuildCustomizer implements BuildCustomizer<GradleBuild> {
+abstract class KotlinGradleBuildCustomizer implements BuildCustomizer<GradleBuild> {
 
-	private final KotlinProjectSettings settings;
+	protected final KotlinProjectSettings settings;
 
 	KotlinGradleBuildCustomizer(KotlinProjectSettings kotlinProjectSettings) {
 		this.settings = kotlinProjectSettings;
 	}
 
 	@Override
-	public void customize(GradleBuild build) {
+	public final void customize(GradleBuild build) {
 		build.addPlugin("org.jetbrains.kotlin.jvm", this.settings.getVersion());
 		build.addPlugin("org.jetbrains.kotlin.plugin.spring", this.settings.getVersion());
 		build.customizeTasksWithType("org.jetbrains.kotlin.gradle.tasks.KotlinCompile",
 				this::customizeKotlinOptions);
 	}
 
-	private void customizeKotlinOptions(TaskCustomization compile) {
-		compile.nested("kotlinOptions", (kotlinOptions) -> {
-			String compilerArgs = this.settings.getCompilerArgs().stream()
-					.map((arg) -> "'" + arg + "'").collect(Collectors.joining(", "));
-			kotlinOptions.set("freeCompilerArgs", "[" + compilerArgs + "]");
-			kotlinOptions.set("jvmTarget", "'" + this.settings.getJvmTarget() + "'");
-		});
-	}
+	protected abstract void customizeKotlinOptions(TaskCustomization compile);
 
 }

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/code/kotlin/KotlinProjectGenerationDefaultContributorsConfiguration.java

@@ -18,6 +18,7 @@ package io.spring.initializr.generator.spring.code.kotlin;
 
 import io.spring.initializr.generator.buildsystem.Build;
 import io.spring.initializr.generator.buildsystem.gradle.GradleBuildSystem;
+import io.spring.initializr.generator.buildsystem.gradle.GradleKtsBuildSystem;
 import io.spring.initializr.generator.buildsystem.maven.MavenBuildSystem;
 import io.spring.initializr.generator.condition.ConditionalOnBuildSystem;
 import io.spring.initializr.generator.condition.ConditionalOnPackaging;
@@ -47,6 +48,7 @@ import org.springframework.context.annotation.Configuration;
  *
  * @author Andy Wilkinson
  * @author Stephane Nicoll
+ * @author Jean-Baptiste Nizet
  */
 @Configuration
 class KotlinProjectGenerationDefaultContributorsConfiguration {
@@ -155,7 +157,7 @@ class KotlinProjectGenerationDefaultContributorsConfiguration {
 	}
 
 	/**
-	 * Configuration for Kotlin projects built with Gradle.
+	 * Configuration for Kotlin projects built with Gradle (Groovy DSL).
 	 *
 	 * @author Andy Wilkinson
 	 */
@@ -166,7 +168,24 @@ class KotlinProjectGenerationDefaultContributorsConfiguration {
 		@Bean
 		public KotlinGradleBuildCustomizer kotlinBuildCustomizer(
 				KotlinProjectSettings kotlinProjectSettings) {
-			return new KotlinGradleBuildCustomizer(kotlinProjectSettings);
+			return new GroovyDslKotlinGradleBuildCustomizer(kotlinProjectSettings);
+		}
+
+	}
+
+	/**
+	 * Configuration for Kotlin projects built with Gradle (Kotlin DSL).
+	 *
+	 * @author Jean-Baptiste Nizet
+	 */
+	@Configuration
+	@ConditionalOnBuildSystem(GradleKtsBuildSystem.ID)
+	static class KotlinGradleKtsProjectConfiguration {
+
+		@Bean
+		public KotlinDslKotlinGradleBuildCustomizer kotlinBuildCustomizer(
+				KotlinProjectSettings kotlinProjectSettings) {
+			return new KotlinDslKotlinGradleBuildCustomizer(kotlinProjectSettings);
 		}
 
 	}

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/scm/git/GitProjectGenerationConfiguration.java

@@ -17,6 +17,7 @@
 package io.spring.initializr.generator.spring.scm.git;
 
 import io.spring.initializr.generator.buildsystem.gradle.GradleBuildSystem;
+import io.spring.initializr.generator.buildsystem.gradle.GradleKtsBuildSystem;
 import io.spring.initializr.generator.buildsystem.maven.MavenBuildSystem;
 import io.spring.initializr.generator.condition.ConditionalOnBuildSystem;
 import io.spring.initializr.generator.project.ProjectGenerationConfiguration;
@@ -56,7 +57,7 @@ public class GitProjectGenerationConfiguration {
 	}
 
 	@Bean
-	@ConditionalOnBuildSystem(GradleBuildSystem.ID)
+	@ConditionalOnBuildSystem({ GradleBuildSystem.ID, GradleKtsBuildSystem.ID })
 	public GitIgnoreCustomizer gradleGitIgnoreCustomizer() {
 		return (gitIgnore) -> {
 			gitIgnore.getGeneral().add(".gradle", "/build/",

initializr-generator-spring/src/test/java/io/spring/initializr/generator/spring/build/BuildComplianceTests.java

@@ -20,6 +20,7 @@ import java.util.stream.Stream;
 
 import io.spring.initializr.generator.buildsystem.BuildSystem;
 import io.spring.initializr.generator.buildsystem.gradle.GradleBuildSystem;
+import io.spring.initializr.generator.buildsystem.gradle.GradleKtsBuildSystem;
 import io.spring.initializr.generator.buildsystem.maven.MavenBuildSystem;
 import io.spring.initializr.generator.language.Language;
 import io.spring.initializr.generator.language.groovy.GroovyLanguage;
@@ -45,6 +46,7 @@ import org.springframework.core.io.ClassPathResource;
  * Build compliance tests.
  *
  * @author Stephane Nicoll
+ * @author Jean-Baptiste Nizet
  */
 class BuildComplianceTests extends AbstractComplianceTests {
 
@@ -54,13 +56,19 @@ class BuildComplianceTests extends AbstractComplianceTests {
 
 	private static final Language kotlin = new KotlinLanguage();
 
-	static Stream<Arguments> parameters() {
+	static Stream<Arguments> previousGenerationParameters() {
 		return Stream.of(
 				Arguments.arguments(BuildSystem.forId(MavenBuildSystem.ID), "pom.xml"),
 				Arguments.arguments(BuildSystem.forId(GradleBuildSystem.ID),
 						"build.gradle"));
 	}
 
+	static Stream<Arguments> parameters() {
+		return Stream.concat(previousGenerationParameters(),
+				Stream.of(Arguments.arguments(BuildSystem.forId(GradleKtsBuildSystem.ID),
+						"build.gradle.kts")));
+	}
+
 	@ParameterizedTest
 	@MethodSource("parameters")
 	void currentGenerationJarJava(BuildSystem build, String fileName) {
@@ -117,19 +125,19 @@ class BuildComplianceTests extends AbstractComplianceTests {
 	}
 
 	@ParameterizedTest
-	@MethodSource("parameters")
+	@MethodSource("previousGenerationParameters")
 	void previousGenerationJarJava(BuildSystem build, String fileName) {
 		testPreviousGenerationJar(java, build, fileName);
 	}
 
 	@ParameterizedTest
-	@MethodSource("parameters")
+	@MethodSource("previousGenerationParameters")
 	void previousGenerationJarGroovy(BuildSystem build, String fileName) {
 		testPreviousGenerationJar(groovy, build, fileName);
 	}
 
 	@ParameterizedTest
-	@MethodSource("parameters")
+	@MethodSource("previousGenerationParameters")
 	void previousGenerationJarKotlin(BuildSystem build, String fileName) {
 		testPreviousGenerationJar(kotlin, build, fileName);
 	}

initializr-generator-spring/src/test/java/io/spring/initializr/generator/spring/build/gradle/GradleKtsProjectGenerationConfigurationTests.java

@@ -0,0 +1,163 @@
+/*
+ * Copyright 2012-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.spring.initializr.generator.spring.build.gradle;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.List;
+import java.util.stream.Stream;
+
+import io.spring.initializr.generator.buildsystem.Dependency;
+import io.spring.initializr.generator.buildsystem.DependencyScope;
+import io.spring.initializr.generator.buildsystem.gradle.GradleKtsBuildSystem;
+import io.spring.initializr.generator.language.java.JavaLanguage;
+import io.spring.initializr.generator.packaging.war.WarPackaging;
+import io.spring.initializr.generator.project.ProjectDescription;
+import io.spring.initializr.generator.spring.build.BuildProjectGenerationConfiguration;
+import io.spring.initializr.generator.spring.build.BuildWriter;
+import io.spring.initializr.generator.spring.test.InitializrMetadataTestBuilder;
+import io.spring.initializr.generator.test.project.ProjectAssetTester;
+import io.spring.initializr.generator.test.project.ProjectStructure;
+import io.spring.initializr.generator.version.Version;
+import io.spring.initializr.metadata.InitializrMetadata;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+
+import org.springframework.util.StreamUtils;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link GradleProjectGenerationConfiguration} with Kotlin DSL build system.
+ *
+ * @author Jean-Baptiste Nizet
+ */
+class GradleKtsProjectGenerationConfigurationTests {
+
+	private ProjectAssetTester projectTester;
+
+	@BeforeEach
+	void setup(@TempDir Path directory) {
+		this.projectTester = new ProjectAssetTester().withIndentingWriterFactory()
+				.withConfiguration(BuildProjectGenerationConfiguration.class,
+						GradleProjectGenerationConfiguration.class)
+				.withDirectory(directory)
+				.withBean(InitializrMetadata.class,
+						() -> InitializrMetadataTestBuilder.withDefaults().build())
+				.withDescriptionCustomizer((description) -> description
+						.setBuildSystem(new GradleKtsBuildSystem()));
+	}
+
+	static Stream<Arguments> supportedPlatformVersions() {
+		// previous versions use gradle < 5, where Kotlin DSL is not supported
+		return Stream.of(Arguments.arguments("2.1.3.RELEASE"));
+	}
+
+	@ParameterizedTest(name = "Spring Boot {0}")
+	@MethodSource("supportedPlatformVersions")
+	void buildWriterIsContributed(String platformVersion) {
+		ProjectDescription description = new ProjectDescription();
+		description.setPlatformVersion(Version.parse(platformVersion));
+		description.setLanguage(new JavaLanguage());
+		BuildWriter buildWriter = this.projectTester.generate(description,
+				(context) -> context.getBean(BuildWriter.class));
+		assertThat(buildWriter)
+				.isInstanceOf(KotlinDslGradleBuildProjectContributor.class);
+	}
+
+	static Stream<Arguments> gradleWrapperParameters() {
+		return Stream.of(Arguments.arguments("2.1.3.RELEASE", "5.2.1"));
+	}
+
+	@ParameterizedTest(name = "Spring Boot {0}")
+	@MethodSource("gradleWrapperParameters")
+	void gradleWrapperIsContributedWhenGeneratingGradleKtsProject(String platformVersion,
+			String expectedGradleVersion) throws IOException {
+		ProjectDescription description = new ProjectDescription();
+		description.setPlatformVersion(Version.parse(platformVersion));
+		description.setLanguage(new JavaLanguage());
+		ProjectStructure projectStructure = this.projectTester.generate(description);
+		List<String> relativePaths = projectStructure.getRelativePathsOfProjectFiles();
+		assertThat(relativePaths).contains("gradlew", "gradlew.bat",
+				"gradle/wrapper/gradle-wrapper.properties",
+				"gradle/wrapper/gradle-wrapper.jar");
+		try (Stream<String> lines = Files.lines(
+				projectStructure.resolve("gradle/wrapper/gradle-wrapper.properties"))) {
+			assertThat(lines.filter((line) -> line
+					.contains(String.format("gradle-%s-bin.zip", expectedGradleVersion))))
+							.hasSize(1);
+		}
+	}
+
+	@Test
+	void buildDotGradleDotKtsIsContributedWhenGeneratingGradleKtsProject()
+			throws IOException {
+		ProjectDescription description = new ProjectDescription();
+		description.setPlatformVersion(Version.parse("2.1.0.RELEASE"));
+		description.setLanguage(new JavaLanguage("11"));
+		description.addDependency("acme",
+				new Dependency("com.example", "acme", DependencyScope.COMPILE));
+		ProjectStructure projectStructure = this.projectTester.generate(description);
+		List<String> relativePaths = projectStructure.getRelativePathsOfProjectFiles();
+		assertThat(relativePaths).contains("build.gradle.kts");
+		Path path = projectStructure.resolve("build.gradle.kts");
+		String[] lines = readAllLines(path);
+		assertThat(lines).containsExactly("plugins {",
+				"    id(\"org.springframework.boot\") version \"2.1.0.RELEASE\"",
+				"    id(\"io.spring.dependency-management\") version \"1.0.6.RELEASE\"",
+				"    java", "}", "", "group = \"com.example\"",
+				"version = \"0.0.1-SNAPSHOT\"",
+				"java.sourceCompatibility = JavaVersion.VERSION_11", "", "repositories {",
+				"    mavenCentral()", "}", "", "dependencies {",
+				"    implementation(\"org.springframework.boot:spring-boot-starter\")",
+				"    implementation(\"com.example:acme\")",
+				"    testImplementation(\"org.springframework.boot:spring-boot-starter-test\")",
+				"}");
+	}
+
+	@Test
+	void warPluginIsAppliedWhenBuildingProjectThatUsesWarPackaging() throws IOException {
+		ProjectDescription description = new ProjectDescription();
+		description.setPlatformVersion(Version.parse("2.1.0.RELEASE"));
+		description.setLanguage(new JavaLanguage());
+		description.setPackaging(new WarPackaging());
+		ProjectStructure projectStructure = this.projectTester.generate(description);
+		List<String> relativePaths = projectStructure.getRelativePathsOfProjectFiles();
+		assertThat(relativePaths).contains("build.gradle.kts");
+		try (Stream<String> lines = Files
+				.lines(projectStructure.resolve("build.gradle.kts"))) {
+			assertThat(lines.filter((line) -> line.contains("    war"))).hasSize(1);
+		}
+	}
+
+	private static String[] readAllLines(Path file) throws IOException {
+		String content = StreamUtils.copyToString(
+				new FileInputStream(new File(file.toString())), StandardCharsets.UTF_8);
+		String[] lines = content.split("\\r?\\n");
+		assertThat(content).endsWith(System.lineSeparator());
+		return lines;
+	}
+
+}

initializr-generator-spring/src/test/java/io/spring/initializr/generator/spring/build/gradle/GradleProjectGenerationConfigurationTests.java

@@ -46,9 +46,10 @@ import org.junit.jupiter.params.provider.MethodSource;
 import static org.assertj.core.api.Assertions.assertThat;
 
 /**
- * Tests for {@link GradleProjectGenerationConfiguration}.
+ * Tests for {@link GradleProjectGenerationConfiguration} with Groovy DSL build system.
  *
  * @author Stephane Nicoll
+ * @author Jean-Baptiste Nizet
  */
 class GradleProjectGenerationConfigurationTests {
 
@@ -81,6 +82,8 @@ class GradleProjectGenerationConfigurationTests {
 		BuildWriter buildWriter = this.projectTester.generate(description,
 				(context) -> context.getBean(BuildWriter.class));
 		assertThat(buildWriter).isInstanceOf(GradleBuildProjectContributor.class);
+		assertThat(buildWriter)
+				.isNotInstanceOf(KotlinDslGradleBuildProjectContributor.class);
 	}
 
 	static Stream<Arguments> gradleWrapperParameters() {

initializr-generator-spring/src/test/java/io/spring/initializr/generator/spring/build/gradle/GroovyDslGradleBuildProjectContributorTests.java

@@ -22,7 +22,7 @@ import java.nio.file.Path;
 import java.util.List;
 
 import io.spring.initializr.generator.buildsystem.gradle.GradleBuild;
-import io.spring.initializr.generator.buildsystem.gradle.GradleBuildWriter;
+import io.spring.initializr.generator.buildsystem.gradle.GroovyDslGradleBuildWriter;
 import io.spring.initializr.generator.io.IndentingWriterFactory;
 import io.spring.initializr.generator.io.SimpleIndentStrategy;
 import io.spring.initializr.generator.test.io.TextTestUtils;
@@ -32,19 +32,21 @@ import org.junit.jupiter.api.io.TempDir;
 import static org.assertj.core.api.Assertions.assertThat;
 
 /**
- * Tests for {@link GradleBuildProjectContributor}.
+ * Tests for {@link GroovyDslGradleBuildProjectContributor}.
  *
  * @author Andy Wilkinson
  * @author Stephane Nicoll
+ * @author Jean-Baptiste Nizet
  */
-class GradleBuildProjectContributorTests {
+class GroovyDslGradleBuildProjectContributorTests {
 
 	@Test
 	void gradleBuildIsContributedInProjectStructure(@TempDir Path projectDir)
 			throws IOException {
 		GradleBuild build = new GradleBuild();
-		new GradleBuildProjectContributor(new GradleBuildWriter(), build,
-				IndentingWriterFactory.withDefaultSettings()).contribute(projectDir);
+		new GroovyDslGradleBuildProjectContributor(new GroovyDslGradleBuildWriter(),
+				build, IndentingWriterFactory.withDefaultSettings())
+						.contribute(projectDir);
 		Path buildGradle = projectDir.resolve("build.gradle");
 		assertThat(buildGradle).isRegularFile();
 	}
@@ -81,8 +83,8 @@ class GradleBuildProjectContributorTests {
 	private List<String> generateBuild(GradleBuild build,
 			IndentingWriterFactory indentingWriterFactory) throws IOException {
 		StringWriter writer = new StringWriter();
-		new GradleBuildProjectContributor(new GradleBuildWriter(), build,
-				indentingWriterFactory).writeBuild(writer);
+		new GroovyDslGradleBuildProjectContributor(new GroovyDslGradleBuildWriter(),
+				build, indentingWriterFactory).writeBuild(writer);
 		return TextTestUtils.readAllLines(writer.toString());
 	}
 

initializr-generator-spring/src/test/java/io/spring/initializr/generator/spring/build/gradle/GroovyDslSettingsGradleProjectContributorTests.java

@@ -31,11 +31,12 @@ import org.junit.jupiter.api.io.TempDir;
 import static org.assertj.core.api.Assertions.assertThat;
 
 /**
- * Tests for {@link SettingsGradleProjectContributor}.
+ * Tests for {@link GroovyDslSettingsGradleProjectContributor}.
  *
  * @author Andy Wilkinson
+ * @author Jean-Baptiste Nizet
  */
-class SettingsGradleProjectContributorTests {
+class GroovyDslSettingsGradleProjectContributorTests {
 
 	@TempDir
 	Path directory;
@@ -77,7 +78,7 @@ class SettingsGradleProjectContributorTests {
 	private List<String> generateSettings(GradleBuild build,
 			IndentingWriterFactory indentingWriterFactory) throws IOException {
 		Path projectDir = Files.createTempDirectory(this.directory, "project-");
-		new SettingsGradleProjectContributor(build, indentingWriterFactory)
+		new GroovyDslSettingsGradleProjectContributor(build, indentingWriterFactory)
 				.contribute(projectDir);
 		return new ProjectStructure(projectDir).readAllLines("settings.gradle");
 	}

initializr-generator-spring/src/test/java/io/spring/initializr/generator/spring/build/gradle/KotlinDslGradleBuildProjectContributorTests.java

@@ -0,0 +1,85 @@
+/*
+ * Copyright 2012-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.spring.initializr.generator.spring.build.gradle;
+
+import java.io.IOException;
+import java.io.StringWriter;
+import java.nio.file.Path;
+import java.util.Arrays;
+import java.util.List;
+
+import io.spring.initializr.generator.buildsystem.gradle.GradleBuild;
+import io.spring.initializr.generator.buildsystem.gradle.KotlinDslGradleBuildWriter;
+import io.spring.initializr.generator.io.IndentingWriterFactory;
+import io.spring.initializr.generator.io.SimpleIndentStrategy;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link KotlinDslGradleBuildProjectContributor}.
+ *
+ * @author Jean-Baptiste Nizet
+ */
+class KotlinDslGradleBuildProjectContributorTests {
+
+	@Test
+	void gradleBuildIsContributedInProjectStructure(@TempDir Path projectDir)
+			throws IOException {
+		GradleBuild build = new GradleBuild();
+		new KotlinDslGradleBuildProjectContributor(new KotlinDslGradleBuildWriter(),
+				build, IndentingWriterFactory.withDefaultSettings())
+						.contribute(projectDir);
+		Path buildGradleKts = projectDir.resolve("build.gradle.kts");
+		assertThat(buildGradleKts).isRegularFile();
+	}
+
+	@Test
+	void gradleBuildIsContributedToProject() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.setGroup("com.example");
+		build.setVersion("1.0.0-SNAPSHOT");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("group = \"com.example\"",
+				"version = \"1.0.0-SNAPSHOT\"");
+	}
+
+	@Test
+	void gradleBuildIsContributedUsingGradleContentId() throws IOException {
+		IndentingWriterFactory indentingWriterFactory = IndentingWriterFactory
+				.create(new SimpleIndentStrategy("    "), (factory) -> factory
+						.indentingStrategy("gradle", new SimpleIndentStrategy("  ")));
+		GradleBuild build = new GradleBuild();
+		build.addPlugin("java");
+		List<String> lines = generateBuild(build, indentingWriterFactory);
+		assertThat(lines).containsSequence("plugins {", "  java", "}");
+	}
+
+	private List<String> generateBuild(GradleBuild build) throws IOException {
+		return generateBuild(build, IndentingWriterFactory.withDefaultSettings());
+	}
+
+	private List<String> generateBuild(GradleBuild build,
+			IndentingWriterFactory indentingWriterFactory) throws IOException {
+		StringWriter writer = new StringWriter();
+		new KotlinDslGradleBuildProjectContributor(new KotlinDslGradleBuildWriter(),
+				build, indentingWriterFactory).writeBuild(writer);
+		return Arrays.asList(writer.toString().split("\\r?\\n"));
+	}
+
+}

initializr-generator-spring/src/test/java/io/spring/initializr/generator/spring/build/gradle/KotlinDslSettingsGradleProjectContributorTests.java

@@ -0,0 +1,86 @@
+/*
+ * Copyright 2012-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.spring.initializr.generator.spring.build.gradle;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.List;
+
+import io.spring.initializr.generator.buildsystem.gradle.GradleBuild;
+import io.spring.initializr.generator.io.IndentingWriterFactory;
+import io.spring.initializr.generator.io.SimpleIndentStrategy;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link KotlinDslSettingsGradleProjectContributor}.
+ *
+ * @author Jean-Baptiste Nizet
+ */
+class KotlinDslSettingsGradleProjectContributorTests {
+
+	@TempDir
+	Path directory;
+
+	@Test
+	void gradleSettingsIsContributedToProject() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.pluginRepositories().add("maven-central");
+		List<String> lines = generateSettings(build);
+		assertThat(lines).containsSequence("pluginManagement {", "    repositories {",
+				"        mavenCentral()", "        gradlePluginPortal()", "    }", "}");
+	}
+
+	@Test
+	void gradleSettingsIsContributedUsingGradleContentId() throws IOException {
+		IndentingWriterFactory indentingWriterFactory = IndentingWriterFactory
+				.create(new SimpleIndentStrategy("    "), (factory) -> factory
+						.indentingStrategy("gradle", new SimpleIndentStrategy("  ")));
+		GradleBuild build = new GradleBuild();
+		build.pluginRepositories().add("maven-central");
+		List<String> lines = generateSettings(build, indentingWriterFactory);
+		assertThat(lines).containsSequence("pluginManagement {", "  repositories {",
+				"    mavenCentral()", "    gradlePluginPortal()", "  }", "}");
+	}
+
+	@Test
+	void gradleSettingsDoesNotUseRepositories() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.repositories().add("maven-central");
+		List<String> lines = generateSettings(build);
+		assertThat(lines).containsSequence("pluginManagement {", "    repositories {",
+				"        gradlePluginPortal()", "    }", "}");
+	}
+
+	private List<String> generateSettings(GradleBuild build) throws IOException {
+		return generateSettings(build, IndentingWriterFactory.withDefaultSettings());
+	}
+
+	private List<String> generateSettings(GradleBuild build,
+			IndentingWriterFactory indentingWriterFactory) throws IOException {
+		Path projectDir = Files.createTempDirectory(this.directory, "project-");
+		new KotlinDslSettingsGradleProjectContributor(build, indentingWriterFactory)
+				.contribute(projectDir);
+		Path settingsGradle = projectDir.resolve("settings.gradle.kts");
+		assertThat(settingsGradle).isRegularFile();
+		return Files.readAllLines(settingsGradle);
+	}
+
+}

initializr-generator-spring/src/test/java/io/spring/initializr/generator/spring/code/kotlin/GroovyDslKotlinGradleBuildCustomizerTests.java

@@ -0,0 +1,73 @@
+/*
+ * Copyright 2012-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.spring.initializr.generator.spring.code.kotlin;
+
+import io.spring.initializr.generator.buildsystem.gradle.GradleBuild;
+import io.spring.initializr.generator.buildsystem.gradle.GradleBuild.TaskCustomization;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link GroovyDslKotlinGradleBuildCustomizer}.
+ *
+ * @author Andy Wilkinson <<<<<<<
+ * HEAD:initializr-generator-spring/src/test/java/io/spring/initializr/generator/spring/code/kotlin/KotlinGradleBuildCustomizerTests.java
+ * @author Jean-Baptiste Nizet ======= >>>>>>> 7ec6a29a... Configure spring project
+ * generation using Gradle Kotlin
+ * DSL:initializr-generator-spring/src/test/java/io/spring/initializr/generator/spring/code/kotlin/GroovyDslKotlinGradleBuildCustomizerTests.java
+ */
+class GroovyDslKotlinGradleBuildCustomizerTests {
+
+	@Test
+	void kotlinPluginsAreConfigured() {
+		GradleBuild build = new GradleBuild();
+		new GroovyDslKotlinGradleBuildCustomizer(
+				new SimpleKotlinProjectSettings("1.2.70")).customize(build);
+		assertThat(build.getPlugins()).hasSize(2);
+		assertThat(build.getPlugins().get(0).getId())
+				.isEqualTo("org.jetbrains.kotlin.jvm");
+		assertThat(build.getPlugins().get(0).getVersion()).isEqualTo("1.2.70");
+		assertThat(build.getPlugins().get(1).getId())
+				.isEqualTo("org.jetbrains.kotlin.plugin.spring");
+		assertThat(build.getPlugins().get(1).getVersion()).isEqualTo("1.2.70");
+	}
+
+	@Test
+	void kotlinCompilationTasksAreCustomized() {
+		GradleBuild build = new GradleBuild();
+		new GroovyDslKotlinGradleBuildCustomizer(
+				new SimpleKotlinProjectSettings("1.2.70")).customize(build);
+		assertThat(build.getTasksWithTypeCustomizations()).hasSize(1);
+		assertThat(build.getTasksWithTypeCustomizations()).containsKeys("KotlinCompile");
+		assertKotlinOptions(build.getTasksWithTypeCustomizations().get("KotlinCompile"));
+	}
+
+	private void assertKotlinOptions(TaskCustomization compileTask) {
+		assertThat(compileTask.getAssignments()).isEmpty();
+		assertThat(compileTask.getInvocations()).isEmpty();
+		assertThat(compileTask.getNested()).hasSize(1);
+		TaskCustomization kotlinOptions = compileTask.getNested().get("kotlinOptions");
+		assertThat(kotlinOptions.getInvocations()).hasSize(0);
+		assertThat(kotlinOptions.getNested()).hasSize(0);
+		assertThat(kotlinOptions.getAssignments()).hasSize(2);
+		assertThat(kotlinOptions.getAssignments())
+				.containsEntry("freeCompilerArgs", "['-Xjsr305=strict']")
+				.containsEntry("jvmTarget", "'1.8'");
+	}
+
+}

initializr-generator-spring/src/test/java/io/spring/initializr/generator/spring/code/kotlin/KotlinDslKotlinGradleBuildCustomizerTests.java

@@ -23,17 +23,17 @@ import org.junit.jupiter.api.Test;
 import static org.assertj.core.api.Assertions.assertThat;
 
 /**
- * Tests for {@link KotlinGradleBuildCustomizer}.
+ * Tests for {@link KotlinDslKotlinGradleBuildCustomizer}.
  *
- * @author Andy Wilkinson
+ * @author Jean-Baptiste Nizet
  */
-class KotlinGradleBuildCustomizerTests {
+class KotlinDslKotlinGradleBuildCustomizerTests {
 
 	@Test
 	void kotlinPluginsAreConfigured() {
 		GradleBuild build = new GradleBuild();
-		new KotlinGradleBuildCustomizer(new SimpleKotlinProjectSettings("1.2.70"))
-				.customize(build);
+		new KotlinDslKotlinGradleBuildCustomizer(
+				new SimpleKotlinProjectSettings("1.2.70")).customize(build);
 		assertThat(build.getPlugins()).hasSize(2);
 		assertThat(build.getPlugins().get(0).getId())
 				.isEqualTo("org.jetbrains.kotlin.jvm");
@@ -46,10 +46,8 @@ class KotlinGradleBuildCustomizerTests {
 	@Test
 	void kotlinCompilationTasksAreCustomized() {
 		GradleBuild build = new GradleBuild();
-		new KotlinGradleBuildCustomizer(new SimpleKotlinProjectSettings("1.2.70"))
-				.customize(build);
-		assertThat(build.getImportedTypes())
-				.contains("org.jetbrains.kotlin.gradle.tasks.KotlinCompile");
+		new KotlinDslKotlinGradleBuildCustomizer(
+				new SimpleKotlinProjectSettings("1.2.70")).customize(build);
 		assertThat(build.getTasksWithTypeCustomizations()).hasSize(1);
 		assertThat(build.getTasksWithTypeCustomizations()).containsKeys("KotlinCompile");
 		assertKotlinOptions(build.getTasksWithTypeCustomizations().get("KotlinCompile"));
@@ -64,8 +62,8 @@ class KotlinGradleBuildCustomizerTests {
 		assertThat(kotlinOptions.getNested()).hasSize(0);
 		assertThat(kotlinOptions.getAssignments()).hasSize(2);
 		assertThat(kotlinOptions.getAssignments())
-				.containsEntry("freeCompilerArgs", "['-Xjsr305=strict']")
-				.containsEntry("jvmTarget", "'1.8'");
+				.containsEntry("freeCompilerArgs", "listOf(\"-Xjsr305=strict\")")
+				.containsEntry("jvmTarget", "\"1.8\"");
 	}
 
 }

initializr-generator-spring/src/test/java/io/spring/initializr/generator/spring/test/InitializrMetadataTestBuilder.java

@@ -80,7 +80,7 @@ public class InitializrMetadataTestBuilder {
 	}
 
 	public InitializrMetadataTestBuilder addAllDefaults() {
-		return addBasicDefaults().setGradleEnv("0.5.1.RELEASE").setKotlinEnv("1.1.1");
+		return addBasicDefaults().setGradleEnv("1.0.6.RELEASE").setKotlinEnv("1.1.1");
 	}
 
 	public InitializrMetadataTestBuilder addBasicDefaults() {

initializr-generator-spring/src/test/resources/project/gradle-kts/annotation-processor-dependency-build.gradle.kts.gen

@@ -0,0 +1,26 @@
+plugins {
+	id("org.springframework.boot") version "2.1.1.RELEASE"
+	id("io.spring.dependency-management") version "1.0.6.RELEASE"
+	java
+}
+
+group = "com.example"
+version = "0.0.1-SNAPSHOT"
+java.sourceCompatibility = JavaVersion.VERSION_1_8
+
+configurations {
+	compileOnly {
+		extendsFrom(configurations.annotationProcessor.get())
+	}
+}
+
+repositories {
+	mavenCentral()
+}
+
+dependencies {
+	implementation("org.springframework.boot:spring-boot-starter-data-jpa")
+	implementation("org.springframework.boot:spring-boot-starter-web")
+	annotationProcessor("org.springframework.boot:spring-boot-configuration-processor")
+	testImplementation("org.springframework.boot:spring-boot-starter-test")
+}

initializr-generator-spring/src/test/resources/project/gradle-kts/bom-ordering-build.gradle.kts.gen

@@ -0,0 +1,26 @@
+plugins {
+	id("org.springframework.boot") version "2.1.1.RELEASE"
+	id("io.spring.dependency-management") version "1.0.6.RELEASE"
+	java
+}
+
+group = "com.example"
+version = "0.0.1-SNAPSHOT"
+java.sourceCompatibility = JavaVersion.VERSION_1_8
+
+repositories {
+	mavenCentral()
+}
+
+dependencies {
+	implementation("org.acme:foo")
+	testImplementation("org.springframework.boot:spring-boot-starter-test")
+}
+
+dependencyManagement {
+	imports {
+		mavenBom("org.acme:bar-bom:1.0")
+		mavenBom("org.acme:biz-bom:1.0")
+		mavenBom("org.acme:foo-bom:1.0")
+	}
+}

initializr-generator-spring/src/test/resources/project/gradle-kts/bom-property-build.gradle.kts.gen

@@ -0,0 +1,26 @@
+plugins {
+	id("org.springframework.boot") version "2.1.1.RELEASE"
+	id("io.spring.dependency-management") version "1.0.6.RELEASE"
+	java
+}
+
+group = "com.example"
+version = "0.0.1-SNAPSHOT"
+java.sourceCompatibility = JavaVersion.VERSION_1_8
+
+repositories {
+	mavenCentral()
+}
+
+extra["fooVersion"] = "1.3.3"
+
+dependencies {
+	implementation("org.acme:foo")
+	testImplementation("org.springframework.boot:spring-boot-starter-test")
+}
+
+dependencyManagement {
+	imports {
+		mavenBom("org.acme:foo-bom:${fooVersion}")
+	}
+}

initializr-generator-spring/src/test/resources/project/gradle-kts/compile-only-dependency-build.gradle.kts.gen

@@ -0,0 +1,20 @@
+plugins {
+	id("org.springframework.boot") version "2.1.1.RELEASE"
+	id("io.spring.dependency-management") version "1.0.6.RELEASE"
+	java
+}
+
+group = "com.example"
+version = "0.0.1-SNAPSHOT"
+java.sourceCompatibility = JavaVersion.VERSION_1_8
+
+repositories {
+	mavenCentral()
+}
+
+dependencies {
+	implementation("org.springframework.boot:spring-boot-starter-data-jpa")
+	implementation("org.springframework.boot:spring-boot-starter-web")
+	compileOnly("org.acme:foo")
+	testImplementation("org.springframework.boot:spring-boot-starter-test")
+}

initializr-generator-spring/src/test/resources/project/gradle-kts/gitignore.gen

@@ -0,0 +1,26 @@
+.gradle
+/build/
+!gradle/wrapper/gradle-wrapper.jar
+
+### STS ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+
+### IntelliJ IDEA ###
+.idea
+*.iws
+*.iml
+*.ipr
+/out/
+
+### NetBeans ###
+/nbproject/private/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/

initializr-generator-spring/src/test/resources/project/gradle-kts/kotlin-java11-build.gradle.kts.gen

@@ -0,0 +1,30 @@
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+
+plugins {
+	id("org.springframework.boot") version "2.1.1.RELEASE"
+	id("io.spring.dependency-management") version "1.0.6.RELEASE"
+	kotlin("jvm") version "1.1.1"
+	kotlin("plugin.spring") version "1.1.1"
+}
+
+group = "com.example"
+version = "0.0.1-SNAPSHOT"
+java.sourceCompatibility = JavaVersion.VERSION_11
+
+repositories {
+	mavenCentral()
+}
+
+dependencies {
+	implementation("org.springframework.boot:spring-boot-starter")
+	implementation("org.jetbrains.kotlin:kotlin-reflect")
+	implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8")
+	testImplementation("org.springframework.boot:spring-boot-starter-test")
+}
+
+tasks.withType<KotlinCompile> {
+	kotlinOptions {
+		freeCompilerArgs = listOf("-Xjsr305=strict")
+		jvmTarget = "1.8"
+	}
+}

initializr-generator-spring/src/test/resources/project/gradle-kts/repositories-build.gradle.kts.gen

@@ -0,0 +1,21 @@
+plugins {
+	id("org.springframework.boot") version "2.1.1.RELEASE"
+	id("io.spring.dependency-management") version "1.0.6.RELEASE"
+	java
+}
+
+group = "com.example"
+version = "0.0.1-SNAPSHOT"
+java.sourceCompatibility = JavaVersion.VERSION_1_8
+
+repositories {
+	mavenCentral()
+	maven { url = uri("https://example.com/foo") }
+	maven { url = uri("https://example.com/bar") }
+}
+
+dependencies {
+	implementation("org.acme:bar")
+	implementation("org.acme:foo")
+	testImplementation("org.springframework.boot:spring-boot-starter-test")
+}

initializr-generator-spring/src/test/resources/project/gradle-kts/repositories-milestone-build.gradle.kts.gen

@@ -0,0 +1,20 @@
+plugins {
+	id("org.springframework.boot") version "2.2.0.M1"
+	id("io.spring.dependency-management") version "1.0.6.RELEASE"
+	java
+}
+
+group = "com.example"
+version = "0.0.1-SNAPSHOT"
+java.sourceCompatibility = JavaVersion.VERSION_1_8
+
+repositories {
+	mavenCentral()
+	maven { url = uri("https://repo.spring.io/snapshot") }
+	maven { url = uri("https://repo.spring.io/milestone") }
+}
+
+dependencies {
+	implementation("org.acme:foo")
+	testImplementation("org.springframework.boot:spring-boot-starter-test")
+}

initializr-generator-spring/src/test/resources/project/gradle-kts/version-override-build.gradle.kts.gen

@@ -0,0 +1,21 @@
+plugins {
+	id("org.springframework.boot") version "2.1.1.RELEASE"
+	id("io.spring.dependency-management") version "1.0.6.RELEASE"
+	java
+}
+
+group = "com.example"
+version = "0.0.1-SNAPSHOT"
+java.sourceCompatibility = JavaVersion.VERSION_1_8
+
+repositories {
+	mavenCentral()
+}
+
+extra["springBarVersion"] = "0.2.0.RELEASE"
+extra["spring-foo.version"] = "0.1.0.RELEASE"
+
+dependencies {
+	implementation("org.springframework.boot:spring-boot-starter-web")
+	testImplementation("org.springframework.boot:spring-boot-starter-test")
+}

initializr-generator-spring/src/test/resources/project/groovy/standard/build.gradle.kts.gen

@@ -0,0 +1,19 @@
+plugins {
+	id("org.springframework.boot") version "2.1.1.RELEASE"
+	id("io.spring.dependency-management") version "1.0.6.RELEASE"
+	groovy
+}
+
+group = "com.example"
+version = "0.0.1-SNAPSHOT"
+java.sourceCompatibility = JavaVersion.VERSION_1_8
+
+repositories {
+	mavenCentral()
+}
+
+dependencies {
+	implementation("org.springframework.boot:spring-boot-starter")
+	implementation("org.codehaus.groovy:groovy")
+	testImplementation("org.springframework.boot:spring-boot-starter-test")
+}

initializr-generator-spring/src/test/resources/project/groovy/standard/war-build.gradle.kts.gen

@@ -0,0 +1,21 @@
+plugins {
+	id("org.springframework.boot") version "2.1.1.RELEASE"
+	id("io.spring.dependency-management") version "1.0.6.RELEASE"
+	war
+	groovy
+}
+
+group = "com.example"
+version = "0.0.1-SNAPSHOT"
+java.sourceCompatibility = JavaVersion.VERSION_1_8
+
+repositories {
+	mavenCentral()
+}
+
+dependencies {
+	implementation("org.springframework.boot:spring-boot-starter-web")
+	implementation("org.codehaus.groovy:groovy")
+	providedRuntime("org.springframework.boot:spring-boot-starter-tomcat")
+	testImplementation("org.springframework.boot:spring-boot-starter-test")
+}

initializr-generator-spring/src/test/resources/project/java/standard/build.gradle.kts.gen

@@ -0,0 +1,18 @@
+plugins {
+	id("org.springframework.boot") version "2.1.1.RELEASE"
+	id("io.spring.dependency-management") version "1.0.6.RELEASE"
+	java
+}
+
+group = "com.example"
+version = "0.0.1-SNAPSHOT"
+java.sourceCompatibility = JavaVersion.VERSION_1_8
+
+repositories {
+	mavenCentral()
+}
+
+dependencies {
+	implementation("org.springframework.boot:spring-boot-starter")
+	testImplementation("org.springframework.boot:spring-boot-starter-test")
+}

initializr-generator-spring/src/test/resources/project/java/standard/war-build.gradle.kts.gen

@@ -0,0 +1,20 @@
+plugins {
+	id("org.springframework.boot") version "2.1.1.RELEASE"
+	id("io.spring.dependency-management") version "1.0.6.RELEASE"
+	java
+	war
+}
+
+group = "com.example"
+version = "0.0.1-SNAPSHOT"
+java.sourceCompatibility = JavaVersion.VERSION_1_8
+
+repositories {
+	mavenCentral()
+}
+
+dependencies {
+	implementation("org.springframework.boot:spring-boot-starter-web")
+	providedRuntime("org.springframework.boot:spring-boot-starter-tomcat")
+	testImplementation("org.springframework.boot:spring-boot-starter-test")
+}

initializr-generator-spring/src/test/resources/project/kotlin/standard/build.gradle.kts.gen

@@ -0,0 +1,30 @@
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+
+plugins {
+	id("org.springframework.boot") version "2.1.1.RELEASE"
+	id("io.spring.dependency-management") version "1.0.6.RELEASE"
+	kotlin("jvm") version "1.1.1"
+	kotlin("plugin.spring") version "1.1.1"
+}
+
+group = "com.example"
+version = "0.0.1-SNAPSHOT"
+java.sourceCompatibility = JavaVersion.VERSION_1_8
+
+repositories {
+	mavenCentral()
+}
+
+dependencies {
+	implementation("org.springframework.boot:spring-boot-starter")
+	implementation("org.jetbrains.kotlin:kotlin-reflect")
+	implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8")
+	testImplementation("org.springframework.boot:spring-boot-starter-test")
+}
+
+tasks.withType<KotlinCompile> {
+	kotlinOptions {
+		freeCompilerArgs = listOf("-Xjsr305=strict")
+		jvmTarget = "1.8"
+	}
+}

initializr-generator-spring/src/test/resources/project/kotlin/standard/war-build.gradle.kts.gen

@@ -0,0 +1,32 @@
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+
+plugins {
+	id("org.springframework.boot") version "2.1.1.RELEASE"
+	id("io.spring.dependency-management") version "1.0.6.RELEASE"
+	war
+	kotlin("jvm") version "1.1.1"
+	kotlin("plugin.spring") version "1.1.1"
+}
+
+group = "com.example"
+version = "0.0.1-SNAPSHOT"
+java.sourceCompatibility = JavaVersion.VERSION_1_8
+
+repositories {
+	mavenCentral()
+}
+
+dependencies {
+	implementation("org.springframework.boot:spring-boot-starter-web")
+	implementation("org.jetbrains.kotlin:kotlin-reflect")
+	implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8")
+	providedRuntime("org.springframework.boot:spring-boot-starter-tomcat")
+	testImplementation("org.springframework.boot:spring-boot-starter-test")
+}
+
+tasks.withType<KotlinCompile> {
+	kotlinOptions {
+		freeCompilerArgs = listOf("-Xjsr305=strict")
+		jvmTarget = "1.8"
+	}
+}

initializr-generator/src/main/java/io/spring/initializr/generator/buildsystem/gradle/Gradle3BuildWriter.java

@@ -19,11 +19,11 @@ package io.spring.initializr.generator.buildsystem.gradle;
 import io.spring.initializr.generator.buildsystem.DependencyScope;
 
 /**
- * A {@link GradleBuildWriter} suitable for Gradle 3.
+ * A {@link GroovyDslGradleBuildWriter} suitable for Gradle 3.
  *
  * @author Stephane Nicoll
  */
-public class Gradle3BuildWriter extends GradleBuildWriter {
+public class Gradle3BuildWriter extends GroovyDslGradleBuildWriter {
 
 	protected String configurationForScope(DependencyScope type) {
 		switch (type) {

initializr-generator/src/main/java/io/spring/initializr/generator/buildsystem/gradle/GradleBuildWriter.java

@@ -43,23 +43,26 @@ import io.spring.initializr.generator.version.VersionProperty;
 import io.spring.initializr.generator.version.VersionReference;
 
 /**
- * A {@link GradleBuild} writer for {@code build.gradle}.
+ * A {@link GradleBuild} writer template for build.gradle and build.gradle.kts. A subclass
+ * of this class exists for the Groovy DSL and for the Kotlin DSL.
  *
  * @author Andy Wilkinson
  * @author Stephane Nicoll
  * @author Jean-Baptiste Nizet
  */
-public class GradleBuildWriter {
+public abstract class GradleBuildWriter {
 
-	public void writeTo(IndentingWriter writer, GradleBuild build) throws IOException {
+	public final void writeTo(IndentingWriter writer, GradleBuild build)
+			throws IOException {
 		writeImports(writer, build);
-		boolean buildScriptWritten = writeBuildscript(writer, build);
-		writePlugins(writer, build, buildScriptWritten);
+		writeBuildscript(writer, build);
+		writePlugins(writer, build);
 		writeProperty(writer, "group", build.getGroup());
 		writeProperty(writer, "version", build.getVersion());
-		writeProperty(writer, "sourceCompatibility", build.getSourceCompatibility());
+		writeJavaSourceCompatibility(writer, build);
+		writer.println();
 		writeConfigurations(writer, build);
-		writeRepositories(writer, build, writer::println);
+		writeRepositories(writer, build);
 		writeProperties(writer, build);
 		writeDependencies(writer, build);
 		writeBoms(writer, build);
@@ -75,61 +78,12 @@ public class GradleBuildWriter {
 		}
 	}
 
-	private boolean writeBuildscript(IndentingWriter writer, GradleBuild build) {
-		List<String> dependencies = build.getBuildscript().getDependencies();
-		Map<String, String> ext = build.getBuildscript().getExt();
-		if (dependencies.isEmpty() && ext.isEmpty()) {
-			return false;
-		}
-		writer.println("buildscript {");
-		writer.indented(() -> {
-			writeBuildscriptExt(writer, build);
-			writeBuildscriptRepositories(writer, build);
-			writeBuildscriptDependencies(writer, build);
-		});
-		writer.println("}");
-		return true;
-	}
+	protected abstract void writeBuildscript(IndentingWriter writer, GradleBuild build);
 
-	private void writeBuildscriptExt(IndentingWriter writer, GradleBuild build) {
-		writeNestedMap(writer, "ext", build.getBuildscript().getExt(),
-				(key, value) -> key + " = " + value);
-	}
+	protected abstract void writePlugins(IndentingWriter writer, GradleBuild build);
 
-	private void writeBuildscriptRepositories(IndentingWriter writer, GradleBuild build) {
-		writeRepositories(writer, build);
-	}
-
-	private void writeBuildscriptDependencies(IndentingWriter writer, GradleBuild build) {
-		writeNestedCollection(writer, "dependencies",
-				build.getBuildscript().getDependencies(),
-				(dependency) -> "classpath '" + dependency + "'");
-	}
-
-	private void writePlugins(IndentingWriter writer, GradleBuild build,
-			boolean buildScriptWritten) {
-		writeNestedCollection(writer, "plugins", build.getPlugins(), this::pluginAsString,
-				determineBeforeWriting(buildScriptWritten, writer));
-		writeCollection(writer, build.getAppliedPlugins(),
-				(plugin) -> "apply plugin: '" + plugin + "'", writer::println);
-		writer.println();
-	}
-
-	private Runnable determineBeforeWriting(boolean buildScriptWritten,
-			IndentingWriter writer) {
-		if (buildScriptWritten) {
-			return writer::println;
-		}
-		return null;
-	}
-
-	private String pluginAsString(GradlePlugin plugin) {
-		String string = "id '" + plugin.getId() + "'";
-		if (plugin.getVersion() != null) {
-			string += " version '" + plugin.getVersion() + "'";
-		}
-		return string;
-	}
+	protected abstract void writeJavaSourceCompatibility(IndentingWriter writer,
+			GradleBuild build);
 
 	private void writeConfigurations(IndentingWriter writer, GradleBuild build) {
 		Map<String, ConfigurationCustomization> configurationCustomizations = build
@@ -137,43 +91,24 @@ public class GradleBuildWriter {
 		if (configurationCustomizations.isEmpty()) {
 			return;
 		}
-		writer.println();
 		writer.println("configurations {");
 		writer.indented(() -> configurationCustomizations.forEach((name,
 				customization) -> writeConfiguration(writer, name, customization)));
 		writer.println("}");
+		writer.println("");
 	}
 
-	private void writeConfiguration(IndentingWriter writer, String configurationName,
-			ConfigurationCustomization configurationCustomization) {
-		if (configurationCustomization.getExtendsFrom().isEmpty()) {
-			writer.println(configurationName);
-		}
-		else {
-			writer.println(configurationName + " {");
-			writer.indented(() -> writer.println(String.format("extendsFrom %s",
-					String.join(", ", configurationCustomization.getExtendsFrom()))));
-			writer.println("}");
-		}
-	}
+	protected abstract void writeConfiguration(IndentingWriter writer,
+			String configurationName,
+			ConfigurationCustomization configurationCustomization);
 
-	private void writeRepositories(IndentingWriter writer, GradleBuild build) {
-		writeRepositories(writer, build, null);
-	}
-
-	private void writeRepositories(IndentingWriter writer, GradleBuild build,
-			Runnable beforeWriting) {
+	protected final void writeRepositories(IndentingWriter writer, GradleBuild build) {
 		writeNestedCollection(writer, "repositories",
 				build.repositories().items().collect(Collectors.toList()),
-				this::repositoryAsString, beforeWriting);
+				this::repositoryAsString);
 	}
 
-	private String repositoryAsString(MavenRepository repository) {
-		if (MavenRepository.MAVEN_CENTRAL.equals(repository)) {
-			return "mavenCentral()";
-		}
-		return "maven { url '" + repository.getUrl() + "' }";
-	}
+	protected abstract String repositoryAsString(MavenRepository repository);
 
 	private void writeProperties(IndentingWriter writer, GradleBuild build) {
 		if (build.getExt().isEmpty() && build.getVersionProperties().isEmpty()) {
@@ -182,19 +117,17 @@ public class GradleBuildWriter {
 		Map<String, String> allProperties = new LinkedHashMap<>(build.getExt());
 		build.getVersionProperties().entrySet().forEach((entry) -> allProperties
 				.put(getVersionPropertyKey(entry), "'" + entry.getValue() + "'"));
-		writeNestedCollection(writer, "ext", allProperties.entrySet(),
-				(e) -> getFormattedProperty(e.getKey(), e.getValue()), writer::println);
+		writeExtraProperties(writer, allProperties);
 	}
 
+	protected abstract void writeExtraProperties(IndentingWriter writer,
+			Map<String, String> allProperties);
+
 	private String getVersionPropertyKey(Entry<VersionProperty, String> entry) {
 		return entry.getKey().isInternal() ? entry.getKey().toCamelCaseFormat()
 				: entry.getKey().toStandardFormat();
 	}
 
-	private String getFormattedProperty(String key, String value) {
-		return String.format("set('%s', %s)", key, value);
-	}
-
 	private void writeDependencies(IndentingWriter writer, GradleBuild build) {
 		Set<Dependency> sortedDependencies = new LinkedHashSet<>();
 		DependencyContainer dependencies = build.dependencies();
@@ -216,15 +149,7 @@ public class GradleBuildWriter {
 				this::dependencyAsString, writer::println);
 	}
 
-	private String dependencyAsString(Dependency dependency) {
-		String quoteStyle = determineQuoteStyle(dependency.getVersion());
-		String version = determineVersion(dependency.getVersion());
-		String type = dependency.getType();
-		return configurationForScope(dependency.getScope()) + " " + quoteStyle
-				+ dependency.getGroupId() + ":" + dependency.getArtifactId()
-				+ ((version != null) ? ":" + version : "")
-				+ ((type != null) ? "@" + type : "") + quoteStyle;
-	}
+	protected abstract String dependencyAsString(Dependency dependency);
 
 	protected String configurationForScope(DependencyScope type) {
 		switch (type) {
@@ -263,23 +188,18 @@ public class GradleBuildWriter {
 	}
 
 	private String bomAsString(BillOfMaterials bom) {
-		String quoteStyle = determineQuoteStyle(bom.getVersion());
 		String version = determineVersion(bom.getVersion());
-		return "mavenBom " + quoteStyle + bom.getGroupId() + ":" + bom.getArtifactId()
-				+ ":" + version + quoteStyle;
+		return bomAsString(bom, version);
 	}
 
-	private String determineQuoteStyle(VersionReference versionReference) {
-		return (versionReference != null && versionReference.isProperty()) ? "\"" : "'";
-	}
+	protected abstract String bomAsString(BillOfMaterials bom, String version);
 
-	private String determineVersion(VersionReference versionReference) {
+	protected final String determineVersion(VersionReference versionReference) {
 		if (versionReference != null) {
 			if (versionReference.isProperty()) {
 				VersionProperty property = versionReference.getProperty();
-				return "${"
-						+ (property.isInternal() ? property.toCamelCaseFormat()
-								: "property('" + property.toStandardFormat() + "')")
+				return "${" + (property.isInternal() ? property.toCamelCaseFormat()
+						: externalVersionPropertyAsString(property.toStandardFormat()))
 						+ "}";
 			}
 			return versionReference.getValue();
@@ -287,33 +207,17 @@ public class GradleBuildWriter {
 		return null;
 	}
 
-	private void writeTasksWithTypeCustomizations(IndentingWriter writer,
-			GradleBuild build) {
-		Map<String, GradleBuild.TaskCustomization> tasksWithTypeCustomizations = build
-				.getTasksWithTypeCustomizations();
-		tasksWithTypeCustomizations.forEach((typeName, customization) -> {
-			writer.println();
-			writer.println("tasks.withType(" + typeName + ") {");
-			writer.indented(() -> writeTaskCustomization(writer, customization));
-			writer.println("}");
-		});
-	}
+	protected abstract String externalVersionPropertyAsString(String standardFormat);
 
-	private void writeTaskCustomizations(IndentingWriter writer, GradleBuild build) {
-		Map<String, TaskCustomization> taskCustomizations = build.getTaskCustomizations();
-		taskCustomizations.forEach((name, customization) -> {
-			writer.println();
-			writer.println(name + " {");
-			writer.indented(() -> writeTaskCustomization(writer, customization));
-			writer.println("}");
-		});
-	}
+	protected abstract void writeTasksWithTypeCustomizations(IndentingWriter writer,
+			GradleBuild build);
 
-	private void writeTaskCustomization(IndentingWriter writer,
+	protected abstract void writeTaskCustomizations(IndentingWriter writer,
+			GradleBuild build);
+
+	protected final void writeTaskCustomization(IndentingWriter writer,
 			TaskCustomization customization) {
-		writeCollection(writer, customization.getInvocations(),
-				(invocation) -> invocation.getTarget() + " "
-						+ String.join(", ", invocation.getArguments()));
+		writeCollection(writer, customization.getInvocations(), this::invocationAsString);
 		writeMap(writer, customization.getAssignments(),
 				(key, value) -> key + " = " + value);
 		customization.getNested().forEach((property, nestedCustomization) -> {
@@ -323,12 +227,14 @@ public class GradleBuildWriter {
 		});
 	}
 
-	private <T> void writeNestedCollection(IndentingWriter writer, String name,
+	protected abstract String invocationAsString(TaskCustomization.Invocation invocation);
+
+	protected final <T> void writeNestedCollection(IndentingWriter writer, String name,
 			Collection<T> collection, Function<T, String> itemToStringConverter) {
 		this.writeNestedCollection(writer, name, collection, itemToStringConverter, null);
 	}
 
-	private <T> void writeNestedCollection(IndentingWriter writer, String name,
+	protected final <T> void writeNestedCollection(IndentingWriter writer, String name,
 			Collection<T> collection, Function<T, String> converter,
 			Runnable beforeWriting) {
 		if (!collection.isEmpty()) {
@@ -347,8 +253,9 @@ public class GradleBuildWriter {
 		writeCollection(writer, collection, converter, null);
 	}
 
-	private <T> void writeCollection(IndentingWriter writer, Collection<T> collection,
-			Function<T, String> itemToStringConverter, Runnable beforeWriting) {
+	protected final <T> void writeCollection(IndentingWriter writer,
+			Collection<T> collection, Function<T, String> itemToStringConverter,
+			Runnable beforeWriting) {
 		if (!collection.isEmpty()) {
 			if (beforeWriting != null) {
 				beforeWriting.run();
@@ -357,25 +264,13 @@ public class GradleBuildWriter {
 		}
 	}
 
-	private <T, U> void writeNestedMap(IndentingWriter writer, String name, Map<T, U> map,
-			BiFunction<T, U, String> converter) {
-		if (!map.isEmpty()) {
-			writer.println(name + " {");
-			writer.indented(() -> writeMap(writer, map, converter));
-			writer.println("}");
-		}
-	}
-
-	private <T, U> void writeMap(IndentingWriter writer, Map<T, U> map,
+	protected final <T, U> void writeMap(IndentingWriter writer, Map<T, U> map,
 			BiFunction<T, U, String> converter) {
 		map.forEach((key, value) -> writer.println(converter.apply(key, value)));
 	}
 
-	private void writeProperty(IndentingWriter writer, String name, String value) {
-		if (value != null) {
-			writer.println(String.format("%s = '%s'", name, value));
-		}
-	}
+	protected abstract void writeProperty(IndentingWriter writer, String name,
+			String value);
 
 	private static Collection<Dependency> filterDependencies(
 			DependencyContainer dependencies, DependencyScope... types) {

initializr-generator/src/main/java/io/spring/initializr/generator/buildsystem/gradle/GradleSettingsWriter.java

@@ -22,15 +22,19 @@ import io.spring.initializr.generator.buildsystem.MavenRepository;
 import io.spring.initializr.generator.io.IndentingWriter;
 
 /**
- * A {@link GradleBuild} writer for {@code settings.gradle}.
+ * A {@link GradleBuild} writer template for {@code settings.gradle} and
+ * {@code settings.gradle.kts}. A subclass of this class exists for the Groovy DSL and for
+ * the Kotlin DSL.
  *
  * @author Andy Wilkinson
+ * @author Jean-Baptiste Nizet
  */
-public class GradleSettingsWriter {
+public abstract class GradleSettingsWriter {
 
-	public void writeTo(IndentingWriter writer, GradleBuild build) throws IOException {
+	public final void writeTo(IndentingWriter writer, GradleBuild build)
+			throws IOException {
 		writePluginManagement(writer, build);
-		writer.println("rootProject.name = '" + build.getArtifact() + "'");
+		writer.println("rootProject.name = " + wrapWithQuotes(build.getArtifact()));
 	}
 
 	private void writePluginManagement(IndentingWriter writer, GradleBuild build) {
@@ -62,7 +66,8 @@ public class GradleSettingsWriter {
 		writer.indented(() -> {
 			writer.println("eachPlugin {");
 			writer.indented(() -> {
-				writer.println("if (requested.id.id == 'org.springframework.boot') {");
+				writer.println("if (requested.id.id == "
+						+ wrapWithQuotes("org.springframework.boot") + ") {");
 				writer.indented(() -> writer.println(
 						"useModule(\"org.springframework.boot:spring-boot-gradle-plugin:${requested.version}\")"));
 				writer.println("}");
@@ -76,7 +81,11 @@ public class GradleSettingsWriter {
 		if (MavenRepository.MAVEN_CENTRAL.equals(repository)) {
 			return "mavenCentral()";
 		}
-		return "maven { url '" + repository.getUrl() + "' }";
+		return "maven { " + urlAssignment(repository.getUrl()) + " }";
 	}
 
+	protected abstract String wrapWithQuotes(String value);
+
+	protected abstract String urlAssignment(String url);
+
 }

initializr-generator/src/main/java/io/spring/initializr/generator/buildsystem/gradle/GroovyDslGradleBuildWriter.java

@@ -0,0 +1,202 @@
+/*
+ * Copyright 2012-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.spring.initializr.generator.buildsystem.gradle;
+
+import java.util.List;
+import java.util.Map;
+import java.util.function.BiFunction;
+
+import io.spring.initializr.generator.buildsystem.BillOfMaterials;
+import io.spring.initializr.generator.buildsystem.Dependency;
+import io.spring.initializr.generator.buildsystem.MavenRepository;
+import io.spring.initializr.generator.io.IndentingWriter;
+import io.spring.initializr.generator.version.VersionReference;
+
+/**
+ * A {@link GradleBuild} writer for {@code build.gradle}.
+ *
+ * @author Jean-Baptiste Nizet
+ */
+public class GroovyDslGradleBuildWriter extends GradleBuildWriter {
+
+	@Override
+	protected void writeBuildscript(IndentingWriter writer, GradleBuild build) {
+		List<String> dependencies = build.getBuildscript().getDependencies();
+		Map<String, String> ext = build.getBuildscript().getExt();
+		if (dependencies.isEmpty() && ext.isEmpty()) {
+			return;
+		}
+		writer.println("buildscript {");
+		writer.indented(() -> {
+			writeBuildscriptExt(writer, build);
+			writeBuildscriptRepositories(writer, build);
+			writeBuildscriptDependencies(writer, build);
+		});
+		writer.println("}");
+		writer.println();
+	}
+
+	private void writeBuildscriptExt(IndentingWriter writer, GradleBuild build) {
+		writeNestedMap(writer, "ext", build.getBuildscript().getExt(),
+				(key, value) -> key + " = " + value);
+	}
+
+	private void writeBuildscriptRepositories(IndentingWriter writer, GradleBuild build) {
+		writeRepositories(writer, build);
+	}
+
+	private void writeBuildscriptDependencies(IndentingWriter writer, GradleBuild build) {
+		writeNestedCollection(writer, "dependencies",
+				build.getBuildscript().getDependencies(),
+				(dependency) -> "classpath '" + dependency + "'");
+	}
+
+	@Override
+	protected void writePlugins(IndentingWriter writer, GradleBuild build) {
+		writeNestedCollection(writer, "plugins", build.getPlugins(),
+				this::pluginAsString);
+		writeCollection(writer, build.getAppliedPlugins(),
+				(plugin) -> "apply plugin: '" + plugin + "'", writer::println);
+		writer.println();
+	}
+
+	private String pluginAsString(GradlePlugin plugin) {
+		String string = "id '" + plugin.getId() + "'";
+		if (plugin.getVersion() != null) {
+			string += " version '" + plugin.getVersion() + "'";
+		}
+		return string;
+	}
+
+	@Override
+	protected void writeJavaSourceCompatibility(IndentingWriter writer,
+			GradleBuild build) {
+		writeProperty(writer, "sourceCompatibility", build.getSourceCompatibility());
+	}
+
+	@Override
+	protected void writeConfiguration(IndentingWriter writer, String configurationName,
+			GradleBuild.ConfigurationCustomization configurationCustomization) {
+		if (configurationCustomization.getExtendsFrom().isEmpty()) {
+			writer.println(configurationName);
+		}
+		else {
+			writer.println(configurationName + " {");
+			writer.indented(() -> writer.println(String.format("extendsFrom %s",
+					String.join(", ", configurationCustomization.getExtendsFrom()))));
+			writer.println("}");
+		}
+	}
+
+	@Override
+	protected String repositoryAsString(MavenRepository repository) {
+		if (MavenRepository.MAVEN_CENTRAL.equals(repository)) {
+			return "mavenCentral()";
+		}
+		return "maven { url '" + repository.getUrl() + "' }";
+	}
+
+	@Override
+	protected void writeExtraProperties(IndentingWriter writer,
+			Map<String, String> allProperties) {
+		writeNestedCollection(writer, "ext", allProperties.entrySet(),
+				(e) -> getFormattedExtraProperty(e.getKey(), e.getValue()),
+				writer::println);
+	}
+
+	private String getFormattedExtraProperty(String key, String value) {
+		return String.format("set('%s', '%s')", key, value);
+	}
+
+	@Override
+	protected String dependencyAsString(Dependency dependency) {
+		String quoteStyle = determineQuoteStyle(dependency.getVersion());
+		String version = determineVersion(dependency.getVersion());
+		String type = dependency.getType();
+		return configurationForScope(dependency.getScope()) + " " + quoteStyle
+				+ dependency.getGroupId() + ":" + dependency.getArtifactId()
+				+ ((version != null) ? ":" + version : "")
+				+ ((type != null) ? "@" + type : "") + quoteStyle;
+	}
+
+	private String determineQuoteStyle(VersionReference versionReference) {
+		return (versionReference != null && versionReference.isProperty()) ? "\"" : "'";
+	}
+
+	@Override
+	protected String bomAsString(BillOfMaterials bom, String version) {
+		String quoteStyle = determineQuoteStyle(bom.getVersion());
+		return "mavenBom " + quoteStyle + bom.getGroupId() + ":" + bom.getArtifactId()
+				+ ":" + version + quoteStyle;
+	}
+
+	@Override
+	protected String externalVersionPropertyAsString(String standardFormat) {
+		return "property('" + standardFormat + "')";
+	}
+
+	@Override
+	protected void writeTasksWithTypeCustomizations(IndentingWriter writer,
+			GradleBuild build) {
+		Map<String, GradleBuild.TaskCustomization> tasksWithTypeCustomizations = build
+				.getTasksWithTypeCustomizations();
+
+		tasksWithTypeCustomizations.forEach((typeName, customization) -> {
+			writer.println();
+			writer.println("tasks.withType(" + typeName + ") {");
+			writer.indented(() -> writeTaskCustomization(writer, customization));
+			writer.println("}");
+		});
+	}
+
+	@Override
+	protected void writeTaskCustomizations(IndentingWriter writer, GradleBuild build) {
+		Map<String, GradleBuild.TaskCustomization> taskCustomizations = build
+				.getTaskCustomizations();
+
+		taskCustomizations.forEach((name, customization) -> {
+			writer.println();
+			writer.println(name + " {");
+			writer.indented(() -> writeTaskCustomization(writer, customization));
+			writer.println("}");
+		});
+	}
+
+	@Override
+	protected String invocationAsString(
+			GradleBuild.TaskCustomization.Invocation invocation) {
+		return invocation.getTarget() + " "
+				+ String.join(", ", invocation.getArguments());
+	}
+
+	@Override
+	protected void writeProperty(IndentingWriter writer, String name, String value) {
+		if (value != null) {
+			writer.println(String.format("%s = '%s'", name, value));
+		}
+	}
+
+	private <T, U> void writeNestedMap(IndentingWriter writer, String name, Map<T, U> map,
+			BiFunction<T, U, String> converter) {
+		if (!map.isEmpty()) {
+			writer.println(name + " {");
+			writer.indented(() -> writeMap(writer, map, converter));
+			writer.println("}");
+		}
+	}
+
+}

initializr-generator/src/main/java/io/spring/initializr/generator/buildsystem/gradle/GroovyDslGradleSettingsWriter.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2012-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.spring.initializr.generator.buildsystem.gradle;
+
+/**
+ * A {@link GradleBuild} writer for {@code settings.gradle}.
+ *
+ * @author Jean-Baptiste Nizet
+ */
+public class GroovyDslGradleSettingsWriter extends GradleSettingsWriter {
+
+	@Override
+	protected String wrapWithQuotes(String value) {
+		return "'" + value + "'";
+	}
+
+	@Override
+	protected String urlAssignment(String url) {
+		return "url " + wrapWithQuotes(url);
+	}
+
+}

initializr-generator/src/main/java/io/spring/initializr/generator/buildsystem/gradle/KotlinDslGradleBuildWriter.java

@@ -0,0 +1,203 @@
+/*
+ * Copyright 2012-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.spring.initializr.generator.buildsystem.gradle;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+import io.spring.initializr.generator.buildsystem.BillOfMaterials;
+import io.spring.initializr.generator.buildsystem.Dependency;
+import io.spring.initializr.generator.buildsystem.MavenRepository;
+import io.spring.initializr.generator.buildsystem.gradle.GradleBuild.ConfigurationCustomization;
+import io.spring.initializr.generator.buildsystem.gradle.GradleBuild.TaskCustomization;
+import io.spring.initializr.generator.io.IndentingWriter;
+
+/**
+ * A {@link GradleBuild} writer for {@code build.gradle.kts}.
+ *
+ * @author Jean-Baptiste Nizet
+ */
+public class KotlinDslGradleBuildWriter extends GradleBuildWriter {
+
+	private static final Map<String, String> sourceCompatibilitiesToJavaVersion = createSourceCompatibilitiesToJavaVersion();
+
+	private static Map<String, String> createSourceCompatibilitiesToJavaVersion() {
+		Map<String, String> result = new HashMap<>();
+		for (int version = 6; version <= 10; version++) {
+			result.put(Integer.toString(version), "VERSION_1_" + version);
+			result.put("1." + version, "VERSION_1_" + version);
+		}
+		for (int version = 11; version <= 12; version++) {
+			result.put(Integer.toString(version), "VERSION_" + version);
+			result.put("1." + version, "VERSION_" + version);
+		}
+
+		return Collections.unmodifiableMap(result);
+	}
+
+	@Override
+	protected void writeBuildscript(IndentingWriter writer, GradleBuild build) {
+		if (!(build.getBuildscript().getDependencies().isEmpty()
+				&& build.getBuildscript().getExt().isEmpty())) {
+			throw new IllegalStateException(
+					"build.gradle.kts scripts shouldn't need a buildscript");
+		}
+	}
+
+	@Override
+	protected void writePlugins(IndentingWriter writer, GradleBuild build) {
+		writeNestedCollection(writer, "plugins", build.getPlugins(), this::pluginAsString,
+				null);
+		writer.println();
+
+		if (!build.getAppliedPlugins().isEmpty()) {
+			throw new IllegalStateException(
+					"build.gradle.kts scripts shouldn't apply plugins. They should use the plugins block instead.");
+		}
+	}
+
+	private String pluginAsString(GradlePlugin plugin) {
+		String result = shortPluginNotation(plugin.getId());
+		if (result == null) {
+			result = "id(\"" + plugin.getId() + "\")";
+		}
+		if (plugin.getVersion() != null) {
+			result += " version \"" + plugin.getVersion() + "\"";
+		}
+		return result;
+	}
+
+	private String shortPluginNotation(String pluginId) {
+		if (pluginId.equals("java") || pluginId.equals("war")
+				|| pluginId.equals("groovy")) {
+			return pluginId;
+		}
+
+		String kotlinPluginPrefix = "org.jetbrains.kotlin.";
+		if (pluginId.startsWith(kotlinPluginPrefix)) {
+			return "kotlin(\"" + pluginId.substring(kotlinPluginPrefix.length()) + "\")";
+		}
+
+		return null;
+	}
+
+	@Override
+	protected void writeJavaSourceCompatibility(IndentingWriter writer,
+			GradleBuild build) {
+		writer.println("java.sourceCompatibility = JavaVersion."
+				+ sourceCompatibilitiesToJavaVersion.get(build.getSourceCompatibility()));
+	}
+
+	@Override
+	protected void writeConfiguration(IndentingWriter writer, String configurationName,
+			ConfigurationCustomization configurationCustomization) {
+		if (configurationCustomization.getExtendsFrom().isEmpty()) {
+			writer.println(configurationName);
+		}
+		else {
+			writer.println(configurationName + " {");
+			writer.indented(() -> writer.println(String.format("extendsFrom(%s)",
+					configurationCustomization.getExtendsFrom().stream()
+							.map((c) -> "configurations." + c + ".get()")
+							.collect(Collectors.joining(", ")))));
+			writer.println("}");
+		}
+	}
+
+	@Override
+	protected String repositoryAsString(MavenRepository repository) {
+		if (MavenRepository.MAVEN_CENTRAL.equals(repository)) {
+			return "mavenCentral()";
+		}
+		return "maven { url = uri(\"" + repository.getUrl() + "\") }";
+	}
+
+	@Override
+	protected String dependencyAsString(Dependency dependency) {
+		String version = determineVersion(dependency.getVersion());
+		String type = dependency.getType();
+		return configurationForScope(dependency.getScope()) + "(\""
+				+ dependency.getGroupId() + ":" + dependency.getArtifactId()
+				+ ((version != null) ? ":" + version : "")
+				+ ((type != null) ? "@" + type : "") + "\")";
+	}
+
+	@Override
+	protected void writeExtraProperties(IndentingWriter writer,
+			Map<String, String> allProperties) {
+		writeCollection(writer, allProperties.entrySet(),
+				(e) -> getFormattedExtraProperty(e.getKey(), e.getValue()),
+				writer::println);
+	}
+
+	private String getFormattedExtraProperty(String key, String value) {
+		return String.format("extra[\"%s\"] = \"%s\"", key, value);
+	}
+
+	@Override
+	protected String bomAsString(BillOfMaterials bom, String version) {
+		return "mavenBom(\"" + bom.getGroupId() + ":" + bom.getArtifactId() + ":"
+				+ version + "\")";
+	}
+
+	@Override
+	protected String externalVersionPropertyAsString(String standardFormat) {
+		return "property(\"" + standardFormat + "\")";
+	}
+
+	@Override
+	protected void writeTasksWithTypeCustomizations(IndentingWriter writer,
+			GradleBuild build) {
+		Map<String, TaskCustomization> tasksWithTypeCustomizations = build
+				.getTasksWithTypeCustomizations();
+
+		tasksWithTypeCustomizations.forEach((typeName, customization) -> {
+			writer.println();
+			writer.println("tasks.withType<" + typeName + "> {");
+			writer.indented(() -> writeTaskCustomization(writer, customization));
+			writer.println("}");
+		});
+	}
+
+	@Override
+	protected void writeTaskCustomizations(IndentingWriter writer, GradleBuild build) {
+		Map<String, TaskCustomization> taskCustomizations = build.getTaskCustomizations();
+
+		taskCustomizations.forEach((name, customization) -> {
+			writer.println();
+			writer.println("tasks." + name + " {");
+			writer.indented(() -> writeTaskCustomization(writer, customization));
+			writer.println("}");
+		});
+	}
+
+	@Override
+	protected String invocationAsString(TaskCustomization.Invocation invocation) {
+		return invocation.getTarget() + "(" + String.join(", ", invocation.getArguments())
+				+ ")";
+	}
+
+	@Override
+	protected void writeProperty(IndentingWriter writer, String name, String value) {
+		if (value != null) {
+			writer.println(String.format("%s = \"%s\"", name, value));
+		}
+	}
+
+}

initializr-generator/src/main/java/io/spring/initializr/generator/buildsystem/gradle/KotlinDslGradleSettingsWriter.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2012-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.spring.initializr.generator.buildsystem.gradle;
+
+/**
+ * A {@link GradleBuild} writer for {@code settings.gradle.kts}.
+ *
+ * @author Jean-Baptiste Nizet
+ */
+public class KotlinDslGradleSettingsWriter extends GradleSettingsWriter {
+
+	@Override
+	protected String wrapWithQuotes(String value) {
+		return "\"" + value + "\"";
+	}
+
+	@Override
+	protected String urlAssignment(String url) {
+		return "url = uri(\"" + url + "\")";
+	}
+
+}

initializr-generator/src/test/java/io/spring/initializr/generator/buildsystem/gradle/GroovyDslGradleBuildWriterTests.java

@@ -30,13 +30,13 @@ import org.junit.jupiter.api.Test;
 import static org.assertj.core.api.Assertions.assertThat;
 
 /**
- * Tests for {@link GradleBuildWriter}
+ * Tests for {@link GroovyDslGradleBuildWriter}
  *
  * @author Andy Wilkinson
  * @author Jean-Baptiste Nizet
  * @author Stephane Nicoll
  */
-class GradleBuildWriterTests {
+class GroovyDslGradleBuildWriterTests {
 
 	@Test
 	void gradleBuildWithCoordinates() throws IOException {
@@ -426,7 +426,7 @@ class GradleBuildWriterTests {
 	}
 
 	private List<String> generateBuild(GradleBuild build) throws IOException {
-		GradleBuildWriter writer = new GradleBuildWriter();
+		GradleBuildWriter writer = new GroovyDslGradleBuildWriter();
 		StringWriter out = new StringWriter();
 		writer.writeTo(new IndentingWriter(out), build);
 		return TextTestUtils.readAllLines(out.toString());

initializr-generator/src/test/java/io/spring/initializr/generator/buildsystem/gradle/GroovyDslGradleSettingsWriterTests.java

@@ -27,11 +27,12 @@ import org.junit.jupiter.api.Test;
 import static org.assertj.core.api.Assertions.assertThat;
 
 /**
- * Tests for {@link GradleSettingsWriter}.
+ * Tests for {@link GroovyDslGradleSettingsWriter}.
  *
  * @author Andy Wilkinson
+ * @author Jean-Baptiste Nizet
  */
-class GradleSettingsWriterTests {
+class GroovyDslGradleSettingsWriterTests {
 
 	@Test
 	void gradleBuildWithMavenCentralPluginRepository() throws IOException {
@@ -81,7 +82,7 @@ class GradleSettingsWriterTests {
 	}
 
 	private List<String> generateSettings(GradleBuild build) throws IOException {
-		GradleSettingsWriter writer = new GradleSettingsWriter();
+		GradleSettingsWriter writer = new GroovyDslGradleSettingsWriter();
 		StringWriter out = new StringWriter();
 		writer.writeTo(new IndentingWriter(out), build);
 		return TextTestUtils.readAllLines(out.toString());

initializr-generator/src/test/java/io/spring/initializr/generator/buildsystem/gradle/KotlinDslGradleBuildWriterTests.java

@@ -0,0 +1,457 @@
+/*
+ * Copyright 2012-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.spring.initializr.generator.buildsystem.gradle;
+
+import java.io.IOException;
+import java.io.StringWriter;
+import java.util.Arrays;
+import java.util.List;
+
+import io.spring.initializr.generator.buildsystem.DependencyScope;
+import io.spring.initializr.generator.io.IndentingWriter;
+import io.spring.initializr.generator.version.VersionProperty;
+import io.spring.initializr.generator.version.VersionReference;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalStateException;
+
+/**
+ * Tests for {@link KotlinDslGradleBuildWriter}
+ *
+ * @author Jean-Baptiste Nizet
+ */
+class KotlinDslGradleBuildWriterTests {
+
+	@Test
+	void gradleBuildWithImports() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.addImportedType(
+				"org.springframework.boot.gradle.tasks.buildinfo.BuildInfo");
+		build.addImportedType("org.jetbrains.kotlin.gradle.tasks.KotlinCompile");
+		build.addImportedType("org.jetbrains.kotlin.gradle.tasks.KotlinCompile"); // same
+																					// import
+																					// added
+																					// twice
+
+		List<String> lines = generateBuild(build);
+		assertThat(lines.subList(0, 3)).containsExactly(
+				"import org.jetbrains.kotlin.gradle.tasks.KotlinCompile",
+				"import org.springframework.boot.gradle.tasks.buildinfo.BuildInfo", "");
+	}
+
+	@Test
+	void gradleBuildWithCoordinates() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.setGroup("com.example");
+		build.setVersion("1.0.1-SNAPSHOT");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).contains("group = \"com.example\"",
+				"version = \"1.0.1-SNAPSHOT\"");
+	}
+
+	@Test
+	void gradleBuildWithSourceCompatibility11() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.setSourceCompatibility("11");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).contains("java.sourceCompatibility = JavaVersion.VERSION_11");
+	}
+
+	@Test
+	void gradleBuildWithSourceCompatibility1Dot8() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.setSourceCompatibility("1.8");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).contains("java.sourceCompatibility = JavaVersion.VERSION_1_8");
+	}
+
+	@Test
+	void gradleBuildWithBuildscriptDependency() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.buildscript((buildscript) -> buildscript.dependency(
+				"org.springframework.boot:spring-boot-gradle-plugin:2.1.0.RELEASE"));
+
+		assertThatIllegalStateException().isThrownBy(() -> {
+			generateBuild(build);
+		});
+	}
+
+	@Test
+	void gradleBuildWithBuildscriptExtProperty() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.buildscript((buildscript) -> buildscript.ext("kotlinVersion", "\1.2.51\""));
+		assertThatIllegalStateException().isThrownBy(() -> {
+			generateBuild(build);
+		});
+	}
+
+	@Test
+	void gradleBuildWithBuiltinPlugin() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.addPlugin("java");
+		build.addPlugin("war");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("plugins {", "    java", "    war", "}");
+	}
+
+	@Test
+	void gradleBuildWithKotlinPluginAndVersion() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.addPlugin("org.jetbrains.kotlin.jvm", "1.3.21");
+		build.addPlugin("org.jetbrains.kotlin.plugin.spring", "1.3.21");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("plugins {",
+				"    kotlin(\"jvm\") version \"1.3.21\"",
+				"    kotlin(\"plugin.spring\") version \"1.3.21\"", "}");
+	}
+
+	@Test
+	void gradleBuildWithPluginAndVersion() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.addPlugin("org.springframework.boot", "2.1.0.RELEASE");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("plugins {",
+				"    id(\"org.springframework.boot\") version \"2.1.0.RELEASE\"", "}");
+	}
+
+	@Test
+	void gradleBuildWithApplyPlugin() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.applyPlugin("io.spring.dependency-management");
+
+		assertThatIllegalStateException().isThrownBy(() -> generateBuild(build));
+	}
+
+	@Test
+	void gradleBuildWithMavenCentralRepository() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.repositories().add("maven-central");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("repositories {", "    mavenCentral()", "}");
+	}
+
+	@Test
+	void gradleBuildWithRepository() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.repositories().add("spring-milestones", "Spring Milestones",
+				"https://repo.spring.io/milestone");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("repositories {",
+				"    maven { url = uri(\"https://repo.spring.io/milestone\") }", "}");
+	}
+
+	@Test
+	void gradleBuildWithSnapshotRepository() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.repositories().add("spring-snapshots", "Spring Snapshots",
+				"https://repo.spring.io/snapshot", true);
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("repositories {",
+				"    maven { url = uri(\"https://repo.spring.io/snapshot\") }", "}");
+	}
+
+	@Test
+	void gradleBuildWithPluginRepository() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.pluginRepositories().add("spring-milestones", "Spring Milestones",
+				"https://repo.spring.io/milestone");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).doesNotContain("repositories {");
+	}
+
+	@Test
+	void gradleBuildWithTaskWithTypesCustomizedWithNestedAssignments()
+			throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.customizeTasksWithType("KotlinCompile", (task) -> {
+			task.nested("kotlinOptions", (kotlinOptions) -> {
+				kotlinOptions.set("freeCompilerArgs", "listOf(\"-Xjsr305=strict\")");
+				kotlinOptions.set("jvmTarget", "\"1.8\"");
+			});
+		});
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("tasks.withType<KotlinCompile> {",
+				"    kotlinOptions {",
+				"        freeCompilerArgs = listOf(\"-Xjsr305=strict\")",
+				"        jvmTarget = \"1.8\"", "    }", "}");
+	}
+
+	@Test
+	void gradleBuildWithTaskCustomizedWithInvocations() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.customizeTask("asciidoctor", (task) -> {
+			task.invoke("inputs.dir", "snippetsDir");
+			task.invoke("dependsOn", "test");
+		});
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("tasks.asciidoctor {",
+				"    inputs.dir(snippetsDir)", "    dependsOn(test)", "}");
+	}
+
+	@Test
+	void gradleBuildWithTaskCustomizedWithAssignments() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.customizeTask("compileKotlin", (task) -> {
+			task.set("kotlinOptions.freeCompilerArgs", "listOf(\"-Xjsr305=strict\")");
+			task.set("kotlinOptions.jvmTarget", "\"1.8\"");
+		});
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("tasks.compileKotlin {",
+				"    kotlinOptions.freeCompilerArgs = listOf(\"-Xjsr305=strict\")",
+				"    kotlinOptions.jvmTarget = \"1.8\"", "}");
+	}
+
+	@Test
+	void gradleBuildWithTaskCustomizedWithNestedCustomization() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.customizeTask("compileKotlin", (compileKotlin) -> compileKotlin
+				.nested("kotlinOptions", (kotlinOptions) -> {
+					kotlinOptions.set("freeCompilerArgs", "listOf(\"-Xjsr305=strict\")");
+					kotlinOptions.set("jvmTarget", "\"1.8\"");
+				}));
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("tasks.compileKotlin {", "    kotlinOptions {",
+				"        freeCompilerArgs = listOf(\"-Xjsr305=strict\")",
+				"        jvmTarget = \"1.8\"", "    }", "}");
+	}
+
+	@Test
+	void gradleBuildWithExt() throws Exception {
+		GradleBuild build = new GradleBuild();
+		build.setGroup("com.example.demo");
+		build.setArtifact("demo");
+		build.ext("java.version", "1.8").ext("alpha", "a");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("extra[\"alpha\"] = \"a\"",
+				"extra[\"java.version\"] = \"1.8\"");
+	}
+
+	@Test
+	void gradleBuildWithVersionProperties() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.addVersionProperty(VersionProperty.of("version.property"), "1.2.3");
+		build.addInternalVersionProperty("internal.property", "4.5.6");
+		build.addExternalVersionProperty("external.property", "7.8.9");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("extra[\"external.property\"] = \"7.8.9\"",
+				"extra[\"internalProperty\"] = \"4.5.6\"",
+				"extra[\"versionProperty\"] = \"1.2.3\"");
+	}
+
+	@Test
+	void gradleBuildWithVersionedDependency() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.dependencies().add("kotlin-stdlib", "org.jetbrains.kotlin",
+				"kotlin-stdlib-jdk8", VersionReference.ofProperty("kotlin.version"),
+				DependencyScope.COMPILE);
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("dependencies {",
+				"    implementation(\"org.jetbrains.kotlin:kotlin-stdlib-jdk8:${kotlinVersion}\")",
+				"}");
+	}
+
+	@Test
+	void gradleBuildWithExternalVersionedDependency() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.dependencies().add("acme", "com.example", "acme",
+				VersionReference.ofProperty(VersionProperty.of("acme.version", false)),
+				DependencyScope.COMPILE);
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("dependencies {",
+				"    implementation(\"com.example:acme:${property(\"acme.version\")}\")",
+				"}");
+	}
+
+	@Test
+	void gradleBuildWithExtAndVersionProperties() throws Exception {
+		GradleBuild build = new GradleBuild();
+		build.setGroup("com.example.demo");
+		build.setArtifact("demo");
+		build.addInternalVersionProperty("test-version", "1.0");
+		build.addExternalVersionProperty("alpha-version", "0.1");
+		build.ext("myProperty", "42");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("extra[\"myProperty\"] = \"42\"",
+				"extra[\"alpha-version\"] = \"0.1\"", "extra[\"testVersion\"] = \"1.0\"");
+	}
+
+	@Test
+	void gradleBuildWithConfiguration() throws Exception {
+		GradleBuild build = new GradleBuild();
+		build.addConfiguration("developmentOnly");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("configurations {", "    developmentOnly",
+				"}");
+	}
+
+	@Test
+	void gradleBuildWithConfigurationCustomization() throws Exception {
+		GradleBuild build = new GradleBuild();
+		build.customizeConfiguration("developmentOnly",
+				(configuration) -> configuration.extendsFrom("compile"));
+		build.customizeConfiguration("developmentOnly",
+				(configuration) -> configuration.extendsFrom("testCompile"));
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("configurations {", "    developmentOnly {",
+				"        extendsFrom(configurations.compile.get(), configurations.testCompile.get())",
+				"    }", "}");
+	}
+
+	@Test
+	void gradleBuildWithConfigurationCustomizations() throws Exception {
+		GradleBuild build = new GradleBuild();
+		build.customizeConfiguration("developmentOnly",
+				(configuration) -> configuration.extendsFrom("compile"));
+		build.customizeConfiguration("testOnly",
+				(configuration) -> configuration.extendsFrom("testCompile"));
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("configurations {", "    developmentOnly {",
+				"        extendsFrom(configurations.compile.get())", "    }",
+				"    testOnly {", "        extendsFrom(configurations.testCompile.get())",
+				"    }", "}");
+	}
+
+	@Test
+	void gradleBuildWithAnnotationProcessorDependency() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.dependencies().add("annotation-processor", "org.springframework.boot",
+				"spring-boot-configuration-processor",
+				DependencyScope.ANNOTATION_PROCESSOR);
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("dependencies {",
+				"    annotationProcessor(\"org.springframework.boot:spring-boot-configuration-processor\")",
+				"}");
+	}
+
+	@Test
+	void gradleBuildWithCompileDependency() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.dependencies().add("root", "org.springframework.boot",
+				"spring-boot-starter", DependencyScope.COMPILE);
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("dependencies {",
+				"    implementation(\"org.springframework.boot:spring-boot-starter\")",
+				"}");
+	}
+
+	@Test
+	void gradleBuildWithRuntimeDependency() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.dependencies().add("driver", "com.example", "jdbc-driver",
+				VersionReference.ofValue("1.0.0"), DependencyScope.RUNTIME);
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("dependencies {",
+				"    runtimeOnly(\"com.example:jdbc-driver:1.0.0\")", "}");
+	}
+
+	@Test
+	void gradleBuildWithProvidedRuntimeDependency() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.dependencies().add("tomcat", "org.springframework.boot",
+				"spring-boot-starter-tomcat", DependencyScope.PROVIDED_RUNTIME);
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("dependencies {",
+				"    providedRuntime(\"org.springframework.boot:spring-boot-starter-tomcat\")",
+				"}");
+	}
+
+	@Test
+	void gradleBuildWithTestCompileDependency() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.dependencies().add("test", "org.springframework.boot",
+				"spring-boot-starter-test", DependencyScope.TEST_COMPILE);
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("dependencies {",
+				"    testImplementation(\"org.springframework.boot:spring-boot-starter-test\")",
+				"}");
+	}
+
+	@Test
+	void gradleBuildWithCompileOnlyDependency() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.dependencies().add("test", "org.springframework.boot",
+				"spring-boot-starter-foobar", DependencyScope.COMPILE_ONLY);
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("dependencies {",
+				"    compileOnly(\"org.springframework.boot:spring-boot-starter-foobar\")",
+				"}");
+	}
+
+	@Test
+	void gradleBuildWithTestRuntimeDependency() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.dependencies().add("embed-mongo", "de.flapdoodle.embed",
+				"de.flapdoodle.embed.mongo", DependencyScope.TEST_RUNTIME);
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("dependencies {",
+				"    testRuntimeOnly(\"de.flapdoodle.embed:de.flapdoodle.embed.mongo\")",
+				"}");
+	}
+
+	@Test
+	void gradleBuildWithNonNullArtifactTypeDependency() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.dependencies().add("root", "org.springframework.boot",
+				"spring-boot-starter", null, DependencyScope.COMPILE, "tar.gz");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("dependencies {",
+				"    implementation(\"org.springframework.boot:spring-boot-starter@tar.gz\")",
+				"}");
+	}
+
+	@Test
+	void gradleBuildWithBom() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.boms().add("test", "com.example", "my-project-dependencies",
+				VersionReference.ofValue("1.0.0.RELEASE"));
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("dependencyManagement {", "    imports {",
+				"        mavenBom(\"com.example:my-project-dependencies:1.0.0.RELEASE\")",
+				"    }", "}");
+	}
+
+	@Test
+	void gradleBuildWithOrderedBoms() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.boms().add("bom1", "com.example", "my-project-dependencies",
+				VersionReference.ofValue("1.0.0.RELEASE"), 5);
+		build.boms().add("bom2", "com.example", "root-dependencies",
+				VersionReference.ofProperty("root.version"), 2);
+		List<String> lines = generateBuild(build);
+		assertThat(lines).containsSequence("dependencyManagement {", "    imports {",
+				"        mavenBom(\"com.example:my-project-dependencies:1.0.0.RELEASE\")",
+				"        mavenBom(\"com.example:root-dependencies:${rootVersion}\")",
+				"    }", "}");
+	}
+
+	@Test
+	void gradleBuildWithCustomVersion() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.setVersion("1.2.4.RELEASE");
+		List<String> lines = generateBuild(build);
+		assertThat(lines).contains("version = \"1.2.4.RELEASE\"");
+	}
+
+	private List<String> generateBuild(GradleBuild build) throws IOException {
+		GradleBuildWriter writer = new KotlinDslGradleBuildWriter();
+		StringWriter out = new StringWriter();
+		writer.writeTo(new IndentingWriter(out), build);
+		return Arrays.asList(out.toString().split("\\r?\\n"));
+	}
+
+}

initializr-generator/src/test/java/io/spring/initializr/generator/buildsystem/gradle/KotlinDslGradleSettingsWriterTests.java

@@ -0,0 +1,90 @@
+/*
+ * Copyright 2012-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.spring.initializr.generator.buildsystem.gradle;
+
+import java.io.IOException;
+import java.io.StringWriter;
+import java.util.Arrays;
+import java.util.List;
+
+import io.spring.initializr.generator.io.IndentingWriter;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link KotlinDslGradleSettingsWriter}.
+ *
+ * @author Jean-Baptiste Nizet
+ */
+class KotlinDslGradleSettingsWriterTests {
+
+	@Test
+	void gradleBuildWithMavenCentralPluginRepository() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.pluginRepositories().add("maven-central");
+		List<String> lines = generateSettings(build);
+		assertThat(lines).containsSequence("pluginManagement {", "    repositories {",
+				"        mavenCentral()", "        gradlePluginPortal()", "    }", "}");
+	}
+
+	@Test
+	void gradleBuildWithPluginRepository() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.pluginRepositories().add("spring-milestones", "Spring Milestones",
+				"https://repo.spring.io/milestone");
+		List<String> lines = generateSettings(build);
+		assertThat(lines).containsSequence("pluginManagement {", "    repositories {",
+				"        maven { url = uri(\"https://repo.spring.io/milestone\") }",
+				"        gradlePluginPortal()", "    }", "    resolutionStrategy {",
+				"        eachPlugin {",
+				"            if (requested.id.id == \"org.springframework.boot\") {",
+				"                useModule(\"org.springframework.boot:spring-boot-gradle-plugin:${requested.version}\")",
+				"            }", "        }", "    }", "}");
+	}
+
+	@Test
+	void gradleBuildWithSnapshotPluginRepository() throws IOException {
+		GradleBuild build = new GradleBuild();
+		build.pluginRepositories().add("spring-snapshots", "Spring Snapshots",
+				"https://repo.spring.io/snapshot", true);
+		List<String> lines = generateSettings(build);
+		assertThat(lines).containsSequence("pluginManagement {", "    repositories {",
+				"        maven { url = uri(\"https://repo.spring.io/snapshot\") }",
+				"        gradlePluginPortal()", "    }", "    resolutionStrategy {",
+				"        eachPlugin {",
+				"            if (requested.id.id == \"org.springframework.boot\") {",
+				"                useModule(\"org.springframework.boot:spring-boot-gradle-plugin:${requested.version}\")",
+				"            }", "        }", "    }", "}");
+	}
+
+	@Test
+	void artifactIdShouldBeUsedAsTheRootProjectName() throws Exception {
+		GradleBuild build = new GradleBuild();
+		build.setArtifact("my-application");
+		List<String> lines = generateSettings(build);
+		assertThat(lines).containsSequence("rootProject.name = \"my-application\"");
+	}
+
+	private List<String> generateSettings(GradleBuild build) throws IOException {
+		GradleSettingsWriter writer = new KotlinDslGradleSettingsWriter();
+		StringWriter out = new StringWriter();
+		writer.writeTo(new IndentingWriter(out), build);
+		return Arrays.asList(out.toString().split("\\r?\\n"));
+	}
+
+}

initializr-web/src/main/java/io/spring/initializr/web/project/MainController.java

@@ -26,7 +26,7 @@ import java.util.Map;
 import java.util.concurrent.TimeUnit;
 
 import io.spring.initializr.generator.buildsystem.BuildSystem;
-import io.spring.initializr.generator.buildsystem.gradle.GradleBuildSystem;
+import io.spring.initializr.generator.buildsystem.maven.MavenBuildSystem;
 import io.spring.initializr.generator.io.template.TemplateRenderer;
 import io.spring.initializr.generator.project.ResolvedProjectDescription;
 import io.spring.initializr.generator.version.Version;
@@ -316,8 +316,7 @@ public class MainController extends AbstractInitializrController {
 
 	private static String getWrapperScript(ResolvedProjectDescription description) {
 		BuildSystem buildSystem = description.getBuildSystem();
-		String script = buildSystem.id().equals(GradleBuildSystem.ID) ? "gradlew"
-				: "mvnw";
+		String script = buildSystem.id().equals(MavenBuildSystem.ID) ? "mvnw" : "gradlew";
 		return (description.getBaseDirectory() != null)
 				? description.getBaseDirectory() + "/" + script : script;
 	}