SPR-6291 - UrlPathHelper is too aggressive decoding URLs

org.springframework.web/src/main/java/org/springframework/web/util/UriUtils.java

@@ -462,6 +462,7 @@ public abstract class UriUtils {
 		Assert.hasLength(encoding, "'encoding' must not be empty");
 		int length = source.length();
 		ByteArrayOutputStream bos = new ByteArrayOutputStream(length);
+		boolean changed = false;
 		for (int i = 0; i < length; i++) {
 			int ch = source.charAt(i);
 			if (ch == '%') {
@@ -472,6 +473,7 @@ public abstract class UriUtils {
 					int l = Character.digit(hex2, 16);
 					bos.write((char) ((u << 4) + l));
 					i += 2;
+					changed = true;
 				}
 				else {
 					throw new IllegalArgumentException("Invalid encoded sequence \"" + source.substring(i) + "\"");
@@ -481,7 +483,7 @@ public abstract class UriUtils {
 				bos.write(ch);
 			}
 		}
-		return new String(bos.toByteArray(), encoding);
+		return changed ? new String(bos.toByteArray(), encoding) : source;
 	}
 
 }

org.springframework.web/src/test/java/org/springframework/web/util/UriUtilsTests.java

@@ -88,11 +88,13 @@ public class UriUtilsTests {
 
 	@Test
 	public void decode() throws UnsupportedEncodingException {
+		assertEquals("Invalid encoded URI", "", UriUtils.decode("", ENC));
 		assertEquals("Invalid encoded URI", "foobar", UriUtils.decode("foobar", ENC));
 		assertEquals("Invalid encoded URI", "foo bar", UriUtils.decode("foo%20bar", ENC));
 		assertEquals("Invalid encoded URI", "foo+bar", UriUtils.decode("foo%2bbar", ENC));
 		assertEquals("Invalid encoded result", "T\u014dky\u014d", UriUtils.decode("T%C5%8Dky%C5%8D", ENC));
 		assertEquals("Invalid encoded result", "/Z\u00fcrich", UriUtils.decode("/Z%C3%BCrich", ENC));
+		assertEquals("Invalid encoded result", "T\u014dky\u014d", UriUtils.decode("T\u014dky\u014d", ENC));
 	}
 
 	@Test(expected = IllegalArgumentException.class)