修复URLUtil.decode无法解码UTF-16问题

CHANGELOG.md

@@ -2,11 +2,12 @@
 # 🚀Changelog
 
 -------------------------------------------------------------------------------------------------------------
-# 5.8.19.M1 (2023-04-16)
+# 5.8.19.M1 (2023-04-17)
 
 ### 🐣新特性
 
 ### 🐞Bug修复
+* 【core  】      修复URLUtil.decode无法解码UTF-16问题（issue#3063@Github）
 
 -------------------------------------------------------------------------------------------------------------
 # 5.8.18 (2023-04-16)

hutool-core/src/main/java/cn/hutool/core/net/URLDecoder.java

@@ -1,6 +1,7 @@
 package cn.hutool.core.net;
 
 import cn.hutool.core.util.CharUtil;
+import cn.hutool.core.util.CharsetUtil;
 import cn.hutool.core.util.StrUtil;
 
 import java.io.ByteArrayOutputStream;
@@ -71,10 +72,41 @@ public class URLDecoder implements Serializable {
 	 * @return 解码后的字符串
 	 */
 	public static String decode(String str, Charset charset, boolean isPlusToSpace) {
-		if(null == charset){
-			return str;
+		if (null == str) {
+			return null;
 		}
-		return StrUtil.str(decode(StrUtil.bytes(str, charset), isPlusToSpace), charset);
+		final int length = str.length();
+		if(0 == length){
+			return StrUtil.EMPTY;
+		}
+
+		final StringBuilder result = new StringBuilder(length / 3);
+
+		int begin = 0;
+		char c;
+		for (int i = 0; i < length; i++) {
+			c = str.charAt(i);
+			if(ESCAPE_CHAR == c || CharUtil.isHexChar(c)){
+				continue;
+			}
+
+			// 遇到非需要处理的字符跳过
+			// 处理之前的hex字符
+			if(i > begin){
+				result.append(decodeSub(str, begin, i, charset, isPlusToSpace));
+			}
+
+			// 非Hex字符，忽略本字符
+			result.append(c);
+			begin = i + 1;
+		}
+
+		// 处理剩余字符
+		if(begin < length){
+			result.append(decodeSub(str, begin, length, charset, isPlusToSpace));
+		}
+
+		return result.toString();
 	}
 
 	/**
@@ -135,4 +167,22 @@ public class URLDecoder implements Serializable {
 		}
 		return buffer.toByteArray();
 	}
+
+	/**
+	 * 解码子串
+	 *
+	 * @param str 字符串
+	 * @param begin 开始位置（包含）
+	 * @param end 结束位置（不包含）
+	 * @param charset 编码
+	 * @param isPlusToSpace 是否+转换为空格
+	 * @return 解码后的字符串
+	 */
+	private static String decodeSub(final String str, final int begin, final int end,
+									final Charset charset, final boolean isPlusToSpace){
+		return new String(decode(
+			// 截取需要decode的部分
+			str.substring(begin, end).getBytes(CharsetUtil.CHARSET_ISO_8859_1), isPlusToSpace
+		), charset);
+	}
 }

hutool-core/src/test/java/cn/hutool/core/net/UrlDecoderTest.java

@@ -1,12 +1,42 @@
 package cn.hutool.core.net;
 
 import cn.hutool.core.util.CharsetUtil;
+import cn.hutool.core.util.URLUtil;
 import org.junit.Assert;
 import org.junit.Test;
 
+import java.io.UnsupportedEncodingException;
+import java.nio.charset.StandardCharsets;
+
 public class UrlDecoderTest {
 	@Test
 	public void decodeForPathTest(){
 		Assert.assertEquals("+", URLDecoder.decodeForPath("+", CharsetUtil.CHARSET_UTF_8));
 	}
+
+	@Test
+	public void issue3063Test() throws UnsupportedEncodingException {
+		// https://github.com/dromara/hutool/issues/3063
+
+		final String s = "测试";
+		final String expectedDecode = "%FE%FF%6D%4B%8B%D5";
+
+		final String s1 = URLUtil.encode(s, StandardCharsets.UTF_16);
+		Assert.assertEquals(expectedDecode, s1);
+		final String s2 = java.net.URLEncoder.encode(s, "UTF-16");
+		Assert.assertEquals(expectedDecode, s2);
+
+		final String decode = URLDecoder.decode(s1, StandardCharsets.UTF_16);
+		Assert.assertEquals(s, decode);
+
+		// 测试编码字符串和非编码字符串混合
+		final String mixDecoded = expectedDecode + "你好";
+		final String decode2 = URLDecoder.decode(mixDecoded, StandardCharsets.UTF_16);
+		Assert.assertEquals("测试你好", decode2);
+
+		Assert.assertEquals(
+			java.net.URLDecoder.decode(mixDecoded, "UTF-16"),
+			URLDecoder.decode(mixDecoded, StandardCharsets.UTF_16)
+		);
+	}
 }