Introduce class name

Closes gh-1425

initializr-generator/src/main/java/io/spring/initializr/generator/language/ClassName.java

@@ -0,0 +1,200 @@
+/*
+ * Copyright 2012-2023 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
+ *
+ *      https://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.language;
+
+import java.util.List;
+import java.util.Objects;
+
+import javax.lang.model.SourceVersion;
+
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
+
+/**
+ * Type reference abstraction to refer to a {@link Class} that is not available on the
+ * classpath.
+ *
+ * @author Stephane Nicoll
+ */
+public final class ClassName {
+
+	private static final List<String> PRIMITIVE_NAMES = List.of("boolean", "byte", "short", "int", "long", "char",
+			"float", "double", "void");
+
+	private final String packageName;
+
+	private final String simpleName;
+
+	private final ClassName enclosingType;
+
+	private String canonicalName;
+
+	private ClassName(String packageName, String simpleName, ClassName enclosingType) {
+		this.packageName = packageName;
+		this.simpleName = simpleName;
+		this.enclosingType = enclosingType;
+	}
+
+	/**
+	 * Create a {@link ClassName} based on the specified fully qualified name. The format
+	 * of the class name must follow {@linkplain Class#getName()}, in particular inner
+	 * classes should be separated by a {@code $}.
+	 * @param fqName the fully qualified name of the class
+	 * @return a class name
+	 */
+	public static ClassName of(String fqName) {
+		Assert.notNull(fqName, "'className' must not be null");
+		if (!isValidClassName(fqName)) {
+			throw new IllegalStateException("Invalid class name '" + fqName + "'");
+		}
+		if (!fqName.contains("$")) {
+			return createClassName(fqName);
+		}
+		String[] elements = fqName.split("(?<!\\$)\\$(?!\\$)");
+		ClassName className = createClassName(elements[0]);
+		for (int i = 1; i < elements.length; i++) {
+			className = new ClassName(className.getPackageName(), elements[i], className);
+		}
+		return className;
+	}
+
+	/**
+	 * Create a {@link ClassName} based on the specified {@link Class}.
+	 * @param type the class to wrap
+	 * @return a class name
+	 */
+	public static ClassName of(Class<?> type) {
+		return of(type.getName());
+	}
+
+	/**
+	 * Return the fully qualified name.
+	 * @return the reflection target name
+	 */
+	public String getName() {
+		ClassName enclosingType = getEnclosingType();
+		String simpleName = getSimpleName();
+		return (enclosingType != null) ? (enclosingType.getName() + '$' + simpleName)
+				: addPackageIfNecessary(simpleName);
+	}
+
+	/**
+	 * Return the package name.
+	 * @return the package name
+	 */
+	public String getPackageName() {
+		return this.packageName;
+	}
+
+	/**
+	 * Return the {@linkplain Class#getSimpleName() simple name}.
+	 * @return the simple name
+	 */
+	public String getSimpleName() {
+		return this.simpleName;
+	}
+
+	/**
+	 * Return the enclosing class name, or {@code null} if this instance does not have an
+	 * enclosing type.
+	 * @return the enclosing type, if any
+	 */
+	public ClassName getEnclosingType() {
+		return this.enclosingType;
+	}
+
+	/**
+	 * Return the {@linkplain Class#getCanonicalName() canonical name}.
+	 * @return the canonical name
+	 */
+	public String getCanonicalName() {
+		if (this.canonicalName == null) {
+			StringBuilder names = new StringBuilder();
+			buildName(this, names);
+			this.canonicalName = addPackageIfNecessary(names.toString());
+		}
+		return this.canonicalName;
+	}
+
+	private boolean isPrimitive() {
+		return isPrimitive(getSimpleName());
+	}
+
+	private static boolean isPrimitive(String name) {
+		return PRIMITIVE_NAMES.stream().anyMatch(name::startsWith);
+	}
+
+	private String addPackageIfNecessary(String part) {
+		if (this.packageName.isEmpty() || this.packageName.equals("java.lang") && isPrimitive()) {
+			return part;
+		}
+		return this.packageName + '.' + part;
+	}
+
+	private static boolean isValidClassName(String className) {
+		for (String s : className.split("\\.", -1)) {
+			String candidate = s.replace("[", "").replace("]", "");
+			if (!SourceVersion.isIdentifier(candidate)) {
+				return false;
+			}
+		}
+		return true;
+	}
+
+	private static ClassName createClassName(String className) {
+		int i = className.lastIndexOf('.');
+		if (i != -1) {
+			return new ClassName(className.substring(0, i), className.substring(i + 1), null);
+		}
+		else {
+			String packageName = (isPrimitive(className)) ? "java.lang" : "";
+			return new ClassName(packageName, className, null);
+		}
+	}
+
+	private static void buildName(ClassName className, StringBuilder sb) {
+		if (className == null) {
+			return;
+		}
+		String typeName = (className.getEnclosingType() != null) ? "." + className.getSimpleName()
+				: className.getSimpleName();
+		sb.insert(0, typeName);
+		buildName(className.getEnclosingType(), sb);
+	}
+
+	@Override
+	public boolean equals(@Nullable Object other) {
+		if (this == other) {
+			return true;
+		}
+		if (!(other instanceof ClassName className)) {
+			return false;
+		}
+		return getCanonicalName().equals(className.getCanonicalName());
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(getCanonicalName());
+	}
+
+	@Override
+	public String toString() {
+		return getCanonicalName();
+	}
+
+}

initializr-generator/src/main/java/io/spring/initializr/generator/language/CodeBlock.java

@@ -37,8 +37,8 @@ import org.springframework.util.ClassUtils;
  * that. Emit {@code "null"} if the value is {@code null}. Does not handle multi-line
  * strings.
  * <li>{@code $T} emits a type reference. Arguments for types may be plain
- * {@linkplain Class classes}, fully qualified class names, and fully qualified
- * functions.</li>
+ * {@linkplain Class classes}, {@linkplain ClassName class names}, fully qualified class
+ * names, and fully qualified functions.</li>
  * <li>{@code $$} emits a dollar sign.
  * <li>{@code $]} ends a statement and emits the configured
  * {@linkplain FormattingOptions#statementSeparator() statement separator}.
@@ -253,9 +253,13 @@ public final class CodeBlock {
 				this.imports.add(type.getName());
 				return type.getSimpleName();
 			}
-			if (arg instanceof String className) {
-				this.imports.add(className);
-				return ClassUtils.getShortName(className);
+			if (arg instanceof ClassName className) {
+				this.imports.add(className.getName());
+				return className.getSimpleName();
+			}
+			if (arg instanceof String fqName) {
+				this.imports.add(fqName);
+				return ClassUtils.getShortName(fqName);
 			}
 			throw new IllegalArgumentException("Failed to extract type from '%s'".formatted(arg));
 		}

initializr-generator/src/test/java/com/example/Example.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2012-2023 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
+ *
+ *      https://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 com.example;
+
+public class Example {
+
+	public static class Inner {
+
+		public static class Nested {
+
+		}
+
+	}
+
+}

initializr-generator/src/test/java/io/spring/initializr/generator/language/ClassNameTests.java

@@ -0,0 +1,169 @@
+/*
+ * Copyright 2012-2023 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
+ *
+ *      https://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.language;
+
+import java.util.stream.Stream;
+
+import com.example.Example;
+import com.example.Example.Inner;
+import com.example.Example.Inner.Nested;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+import org.junit.jupiter.params.provider.ValueSource;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalStateException;
+
+/**
+ * Tests for {@link ClassName}.
+ *
+ * @author Stephane Nicoll
+ */
+class ClassNameTests {
+
+	@Test
+	void classNameWithTopLevelClassName() {
+		classNameWithTopLevelClass(ClassName.of("com.example.Example"));
+	}
+
+	@Test
+	void classNameWithTopLevelClass() {
+		classNameWithTopLevelClass(ClassName.of(Example.class));
+	}
+
+	private void classNameWithTopLevelClass(ClassName className) {
+		assertThat(className.getName()).isEqualTo("com.example.Example");
+		assertThat(className.getCanonicalName()).isEqualTo("com.example.Example");
+		assertThat(className.getPackageName()).isEqualTo("com.example");
+		assertThat(className.getSimpleName()).isEqualTo("Example");
+		assertThat(className.getEnclosingType()).isNull();
+	}
+
+	@Test
+	void classNameWithInnerClassName() {
+		classNameWithInnerClass(ClassName.of("com.example.Example$Inner"));
+	}
+
+	@Test
+	void classNameWithInnerClass() {
+		classNameWithInnerClass(ClassName.of(Inner.class));
+	}
+
+	private void classNameWithInnerClass(ClassName className) {
+		assertThat(className.getName()).isEqualTo("com.example.Example$Inner");
+		assertThat(className.getCanonicalName()).isEqualTo("com.example.Example.Inner");
+		assertThat(className.getPackageName()).isEqualTo("com.example");
+		assertThat(className.getSimpleName()).isEqualTo("Inner");
+		assertThat(className.getEnclosingType()).satisfies((enclosingType) -> {
+			assertThat(enclosingType.getCanonicalName()).isEqualTo("com.example.Example");
+			assertThat(enclosingType.getPackageName()).isEqualTo("com.example");
+			assertThat(enclosingType.getSimpleName()).isEqualTo("Example");
+			assertThat(enclosingType.getEnclosingType()).isNull();
+		});
+	}
+
+	@Test
+	void classNameWithNestedInnerClassName() {
+		classNameWithNestedInnerClass(ClassName.of("com.example.Example$Inner$Nested"));
+	}
+
+	@Test
+	void classNameWithNestedInnerClass() {
+		classNameWithNestedInnerClass(ClassName.of(Nested.class));
+	}
+
+	private void classNameWithNestedInnerClass(ClassName className) {
+		assertThat(className.getName()).isEqualTo("com.example.Example$Inner$Nested");
+		assertThat(className.getCanonicalName()).isEqualTo("com.example.Example.Inner.Nested");
+		assertThat(className.getPackageName()).isEqualTo("com.example");
+		assertThat(className.getSimpleName()).isEqualTo("Nested");
+		assertThat(className.getEnclosingType()).satisfies((enclosingType) -> {
+			assertThat(enclosingType.getCanonicalName()).isEqualTo("com.example.Example.Inner");
+			assertThat(enclosingType.getPackageName()).isEqualTo("com.example");
+			assertThat(enclosingType.getSimpleName()).isEqualTo("Inner");
+			assertThat(enclosingType.getEnclosingType()).satisfies((parentEnclosingType) -> {
+				assertThat(parentEnclosingType.getCanonicalName()).isEqualTo("com.example.Example");
+				assertThat(parentEnclosingType.getPackageName()).isEqualTo("com.example");
+				assertThat(parentEnclosingType.getSimpleName()).isEqualTo("Example");
+				assertThat(parentEnclosingType.getEnclosingType()).isNull();
+			});
+		});
+	}
+
+	@ParameterizedTest
+	@MethodSource("primitivesAndPrimitivesArray")
+	void primitivesAreHandledProperly(ClassName className, String expectedName) {
+		assertThat(className.getName()).isEqualTo(expectedName);
+		assertThat(className.getCanonicalName()).isEqualTo(expectedName);
+		assertThat(className.getPackageName()).isEqualTo("java.lang");
+	}
+
+	static Stream<Arguments> primitivesAndPrimitivesArray() {
+		return Stream.of(Arguments.of(ClassName.of("boolean"), "boolean"), Arguments.of(ClassName.of("byte"), "byte"),
+				Arguments.of(ClassName.of("short"), "short"), Arguments.of(ClassName.of("int"), "int"),
+				Arguments.of(ClassName.of("long"), "long"), Arguments.of(ClassName.of("char"), "char"),
+				Arguments.of(ClassName.of("float"), "float"), Arguments.of(ClassName.of("double"), "double"),
+				Arguments.of(ClassName.of("boolean[]"), "boolean[]"), Arguments.of(ClassName.of("byte[]"), "byte[]"),
+				Arguments.of(ClassName.of("short[]"), "short[]"), Arguments.of(ClassName.of("int[]"), "int[]"),
+				Arguments.of(ClassName.of("long[]"), "long[]"), Arguments.of(ClassName.of("char[]"), "char[]"),
+				Arguments.of(ClassName.of("float[]"), "float[]"), Arguments.of(ClassName.of("double[]"), "double[]"));
+	}
+
+	@ParameterizedTest
+	@MethodSource("arrays")
+	void arraysHaveSuitableReflectionTargetName(ClassName typeReference, String expectedName) {
+		assertThat(typeReference.getName()).isEqualTo(expectedName);
+	}
+
+	static Stream<Arguments> arrays() {
+		return Stream.of(Arguments.of(ClassName.of("java.lang.Object[]"), "java.lang.Object[]"),
+				Arguments.of(ClassName.of("java.lang.Integer[]"), "java.lang.Integer[]"),
+				Arguments.of(ClassName.of("com.example.Test[]"), "com.example.Test[]"));
+	}
+
+	@Test
+	void classNameInRootPackage() {
+		ClassName type = ClassName.of("MyRootClass");
+		assertThat(type.getCanonicalName()).isEqualTo("MyRootClass");
+		assertThat(type.getPackageName()).isEmpty();
+	}
+
+	@ParameterizedTest(name = "{0}")
+	@ValueSource(strings = { "com.example.Tes(t", "com.example..Test" })
+	void classNameWithInvalidClassName(String invalidClassName) {
+		assertThatIllegalStateException().isThrownBy(() -> ClassName.of(invalidClassName))
+			.withMessageContaining("Invalid class name");
+	}
+
+	@Test
+	void equalsWithIdenticalNameIsTrue() {
+		assertThat(ClassName.of(String.class)).isEqualTo(ClassName.of("java.lang.String"));
+	}
+
+	@Test
+	void equalsWithNonClassNameIsFalse() {
+		assertThat(ClassName.of(String.class)).isNotEqualTo("java.lang.String");
+	}
+
+	@Test
+	void toStringUsesCanonicalName() {
+		assertThat(ClassName.of(String.class)).hasToString("java.lang.String");
+	}
+
+}

initializr-generator/src/test/java/io/spring/initializr/generator/language/CodeBlockTests.java

@@ -125,6 +125,13 @@ class CodeBlockTests {
 
 	@Test
 	void codeBlockWithTypePlaceholderAndClassNameAddsImport() {
+		CodeBlock code = CodeBlock.of("return $T.truncate(myString)", ClassName.of(StringUtils.class));
+		assertThat(writeJava(code)).isEqualTo("return StringUtils.truncate(myString)");
+		assertThat(code.getImports()).containsExactly(StringUtils.class.getName());
+	}
+
+	@Test
+	void codeBlockWithTypePlaceholderAndFullyQualifiedClassNameAddsImport() {
 		CodeBlock code = CodeBlock.of("return $T.truncate(myString)", "com.example.StringUtils");
 		assertThat(writeJava(code)).isEqualTo("return StringUtils.truncate(myString)");
 		assertThat(code.getImports()).containsExactly("com.example.StringUtils");