Avoid unnecessary computation of cleaned URL

Closes gh-25531

(cherry picked from commit 96a4e11)

Author: jhoeller

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -56,7 +56,8 @@ public class UrlResource extends AbstractFileResolvingResource {
 	/**
 	 * Cleaned URL (with normalized path), used for comparisons.
 	 */
-	private final URL cleanedUrl;
+	@Nullable
+	private volatile URL cleanedUrl;
 
 
 	/**
@@ -69,7 +70,6 @@ public UrlResource(URI uri) throws MalformedURLException {
 		Assert.notNull(uri, "URI must not be null");
 		this.uri = uri;
 		this.url = uri.toURL();
-		this.cleanedUrl = getCleanedUrl(this.url, uri.toString());
 	}
 
 	/**
@@ -78,9 +78,8 @@ public UrlResource(URI uri) throws MalformedURLException {
 	 */
 	public UrlResource(URL url) {
 		Assert.notNull(url, "URL must not be null");
-		this.url = url;
-		this.cleanedUrl = getCleanedUrl(this.url, url.toString());
 		this.uri = null;
+		this.url = url;
 	}
 
 	/**
@@ -127,7 +126,6 @@ public UrlResource(String protocol, String location, @Nullable String fragment)
 		try {
 			this.uri = new URI(protocol, location, fragment);
 			this.url = this.uri.toURL();
-			this.cleanedUrl = getCleanedUrl(this.url, this.uri.toString());
 		}
 		catch (URISyntaxException ex) {
 			MalformedURLException exToThrow = new MalformedURLException(ex.getMessage());
@@ -144,7 +142,7 @@ public UrlResource(String protocol, String location, @Nullable String fragment)
 	 * @return the cleaned URL (possibly the original URL as-is)
 	 * @see org.springframework.util.StringUtils#cleanPath
 	 */
-	private URL getCleanedUrl(URL originalUrl, String originalPath) {
+	private static URL getCleanedUrl(URL originalUrl, String originalPath) {
 		String cleanedPath = StringUtils.cleanPath(originalPath);
 		if (!cleanedPath.equals(originalPath)) {
 			try {
@@ -157,6 +155,21 @@ private URL getCleanedUrl(URL originalUrl, String originalPath) {
 		return originalUrl;
 	}
 
+	/**
+	 * Lazily determine a cleaned URL for the given original URL.
+	 * @see #getCleanedUrl(URL, String)
+	 */
+	private URL getCleanedUrl() {
+		URL cleanedUrl = this.cleanedUrl;
+		if (cleanedUrl != null) {
+			return cleanedUrl;
+		}
+		cleanedUrl = getCleanedUrl(this.url, (this.uri != null ? this.uri : this.url).toString());
+		this.cleanedUrl = cleanedUrl;
+		return cleanedUrl;
+	}
+
+
 	/**
 	 * This implementation opens an InputStream for the given URL.
 	 * <p>It sets the {@code useCaches} flag to {@code false},
@@ -247,7 +260,7 @@ public Resource createRelative(String relativePath) throws MalformedURLException
 	 */
 	@Override
 	public String getFilename() {
-		return StringUtils.getFilename(this.cleanedUrl.getPath());
+		return StringUtils.getFilename(getCleanedUrl().getPath());
 	}
 
 	/**
@@ -265,15 +278,15 @@ public String getDescription() {
 	@Override
 	public boolean equals(Object other) {
 		return (this == other || (other instanceof UrlResource &&
-				this.cleanedUrl.equals(((UrlResource) other).cleanedUrl)));
+				getCleanedUrl().equals(((UrlResource) other).getCleanedUrl())));
 	}
 
 	/**
 	 * This implementation returns the hash code of the underlying URL reference.
 	 */
 	@Override
 	public int hashCode() {
-		return this.cleanedUrl.hashCode();
+		return getCleanedUrl().hashCode();
 	}
 
 }