Cache lookup path in ResourceUrlEncodingFilter

Commit https://github.com/spring-projects/spring-framework/commit/2b97d6
introduced a change where the path within the DispatcherServlet is
determined with each call to ResourceUrlProvider.getForRequestUrl.

To avoid repeating that every time a URL is encoded through the
response, we now cache the result of the lookupPath determination in
ResourceUrlEncodingFilter.

Issue: SPR-12332

spring-webmvc/src/main/java/org/springframework/web/servlet/resource/ResourceUrlEncodingFilter.java

@@ -57,6 +57,9 @@ public class ResourceUrlEncodingFilter extends OncePerRequestFilter {
 
 		private HttpServletRequest request;
 
+		/* Cache the index of the path within the DispatcherServlet mapping. */
+		private Integer indexLookupPath;
+
 
 		private ResourceUrlEncodingResponseWrapper(HttpServletRequest request, HttpServletResponse wrapped) {
 			super(wrapped);
@@ -70,8 +73,11 @@ public class ResourceUrlEncodingFilter extends OncePerRequestFilter {
 				logger.debug("Request attribute exposing ResourceUrlProvider not found.");
 				return super.encodeURL(url);
 			}
-			String resolvedUrl = resourceUrlProvider.getForRequestUrl(this.request, url);
-			return (resolvedUrl != null ? super.encodeURL(resolvedUrl) : super.encodeURL(url));
+			initIndexLookupPath(resourceUrlProvider);
+			String prefix = url.substring(0, this.indexLookupPath);
+			String lookupPath = url.substring(this.indexLookupPath);
+			lookupPath = resourceUrlProvider.getForLookupPath(lookupPath);
+			return (lookupPath != null ? super.encodeURL(prefix + lookupPath) : super.encodeURL(url));
 		}
 
 		private ResourceUrlProvider getResourceUrlProvider() {
@@ -79,6 +85,13 @@ public class ResourceUrlEncodingFilter extends OncePerRequestFilter {
 			return (ResourceUrlProvider) this.request.getAttribute(name);
 		}
 
+		private void initIndexLookupPath(ResourceUrlProvider urlProvider) {
+			if (this.indexLookupPath == null) {
+				String requestUri = urlProvider.getPathHelper().getRequestUri(this.request);
+				String lookupPath = urlProvider.getPathHelper().getLookupPathForRequest(this.request);
+				this.indexLookupPath = requestUri.indexOf(lookupPath);
+			}
+		}
 	}
 
 }

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

@@ -79,7 +79,7 @@ public class ResourceUrlProviderJavaConfigTests {
 	}
 
 	@Test
-	public void resolvePathWithServletMappingByPrefix() throws Exception {
+	public void resolvePathWithServletMappedByPrefix() throws Exception {
 		this.request.setRequestURI("/myapp/myservlet/index");
 		this.request.setServletPath("/myservlet");
 		this.filterChain.doFilter(this.request, this.response);
@@ -88,6 +88,16 @@ public class ResourceUrlProviderJavaConfigTests {
 				resolvePublicResourceUrlPath("/myapp/myservlet/resources/foo.css"));
 	}
 
+	@Test
+	public void resolvePathNoMatch() throws Exception {
+		this.request.setRequestURI("/myapp/myservlet/index");
+		this.request.setServletPath("/myservlet");
+		this.filterChain.doFilter(this.request, this.response);
+
+		assertEquals("/myapp/myservlet/index", resolvePublicResourceUrlPath("/myapp/myservlet/index"));
+	}
+
+
 	private String resolvePublicResourceUrlPath(String path) {
 		return this.servlet.wrappedResponse.encodeURL(path);
 	}