Avoid use of java.net.URL constructors (for JDK 20 compatibility)

Explicit path computation also leads to consistent relative path semantics for resource URLs.

Closes gh-29481
Closes gh-28522

spring-core/src/main/java/org/springframework/core/io/UrlResource.java

@@ -89,33 +89,31 @@ public class UrlResource extends AbstractFileResolvingResource {
 	}
 
 	/**
-	 * Create a new {@code UrlResource} based on a URL path.
+	 * Create a new {@code UrlResource} based on a URI path.
 	 * <p>Note: The given path needs to be pre-encoded if necessary.
-	 * @param path a URL path
-	 * @throws MalformedURLException if the given URL path is not valid
-	 * @see java.net.URL#URL(String)
+	 * @param path a URI path
+	 * @throws MalformedURLException if the given URI path is not valid
+	 * @see ResourceUtils#toURI(String)
 	 */
 	public UrlResource(String path) throws MalformedURLException {
 		Assert.notNull(path, "Path must not be null");
+		String cleanedPath = StringUtils.cleanPath(path);
+		URI uri;
+		URL url;
 
-		// Equivalent without java.net.URL constructor - for building on JDK 20+
-		/*
 		try {
-			String cleanedPath = StringUtils.cleanPath(path);
-			this.uri = ResourceUtils.toURI(cleanedPath);
-			this.url = this.uri.toURL();
-			this.cleanedUrl = cleanedPath;
+			// Prefer URI construction with toURL conversion (as of 6.1)
+			uri = ResourceUtils.toURI(cleanedPath);
+			url = uri.toURL();
 		}
 		catch (URISyntaxException | IllegalArgumentException ex) {
-			MalformedURLException exToThrow = new MalformedURLException(ex.getMessage());
-			exToThrow.initCause(ex);
-			throw exToThrow;
+			uri = null;
+			url = ResourceUtils.toURL(path);
 		}
-		*/
 
-		this.uri = null;
-		this.url = ResourceUtils.toURL(path);
-		this.cleanedUrl = StringUtils.cleanPath(path);
+		this.uri = uri;
+		this.url = url;
+		this.cleanedUrl = cleanedPath;
 	}
 
 	/**

spring-core/src/main/java/org/springframework/util/ResourceUtils.java

@@ -390,21 +390,18 @@ public abstract class ResourceUtils {
 	 * @throws MalformedURLException if the location wasn't a valid URL
 	 * @since 6.0
 	 */
+	@SuppressWarnings("deprecation")  // on JDK 20
 	public static URL toURL(String location) throws MalformedURLException {
-		// Equivalent without java.net.URL constructor - for building on JDK 20+
-		/*
 		try {
+			// Prefer URI construction with toURL conversion (as of 6.1)
 			return toURI(StringUtils.cleanPath(location)).toURL();
 		}
 		catch (URISyntaxException | IllegalArgumentException ex) {
-			MalformedURLException exToThrow = new MalformedURLException(ex.getMessage());
-			exToThrow.initCause(ex);
-			throw exToThrow;
-		}
-		*/
-
+			// Lenient fallback to deprecated (on JDK 20) URL constructor,
+			// e.g. for decoded location Strings with percent characters.
 			return new URL(location);
 		}
+	}
 
 	/**
 	 * Create a URL instance for the given root URL and relative path,
@@ -419,12 +416,7 @@ public abstract class ResourceUtils {
 		// # can appear in filenames, java.net.URL should not treat it as a fragment
 		relativePath = StringUtils.replace(relativePath, "#", "%23");
 
-		// Equivalent without java.net.URL constructor - for building on JDK 20+
-		/*
 		return toURL(StringUtils.applyRelativePath(root.toString(), relativePath));
-		*/
-
-		return new URL(root, relativePath);
 	}
 
 	/**

spring-webflux/src/test/java/org/springframework/web/reactive/resource/PathResourceResolverTests.java

@@ -40,7 +40,6 @@ public class PathResourceResolverTests {
 
 	private static final Duration TIMEOUT = Duration.ofSeconds(5);
 
-
 	private final PathResourceResolver resolver = new PathResourceResolver();
 
 
@@ -111,7 +110,11 @@ public class PathResourceResolverTests {
 	@Test  // gh-23463
 	public void ignoreInvalidEscapeSequence() throws IOException {
 		UrlResource location = new UrlResource(getClass().getResource("./test/"));
-		Resource resource = location.createRelative("test%file.txt");
+
+		Resource resource = new UrlResource(location.getURL() + "test%file.txt");
+		assertThat(this.resolver.checkResource(resource, location)).isTrue();
+
+		resource = location.createRelative("test%file.txt");
 		assertThat(this.resolver.checkResource(resource, location)).isTrue();
 	}
 

spring-webmvc/src/test/java/org/springframework/web/servlet/resource/PathResourceResolverTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -95,7 +95,11 @@ public class PathResourceResolverTests {
 	@Test  // gh-23463
 	public void ignoreInvalidEscapeSequence() throws IOException {
 		UrlResource location = new UrlResource(getClass().getResource("./test/"));
-		Resource resource = location.createRelative("test%file.txt");
+
+		Resource resource = new UrlResource(location.getURL() + "test%file.txt");
+		assertThat(this.resolver.checkResource(resource, location)).isTrue();
+
+		resource = location.createRelative("test%file.txt");
 		assertThat(this.resolver.checkResource(resource, location)).isTrue();
 	}