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/*
* Copyright 2002-2015 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.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.web.servlet.resource;
import java.util.List;
import javax.servlet.http.HttpServletRequest;
import org.webjars.MultipleMatchesException;
import org.webjars.WebJarAssetLocator;
import org.springframework.core.io.Resource;
/**
* A {@code ResourceResolver} that delegates to the chain to locate a resource and then
* attempts to find a matching versioned resource contained in a WebJar JAR file.
*
* <p>This allows WebJars.org users to write version agnostic paths in their templates,
* like {@code <script src="/jquery/jquery.min.js"/>}.
* This path will be resolved to the unique version {@code <script src="/jquery/1.2.0/jquery.min.js"/>},
* which is a better fit for HTTP caching and version management in applications.
*
* <p>This also resolves resources for version agnostic HTTP requests {@code "GET /jquery/jquery.min.js"}.
*
* <p>This resolver requires the "org.webjars:webjars-locator" library on classpath,
* and is automatically registered if that library is present.
*
* @author Brian Clozel
* @since 4.2
* @see org.springframework.web.servlet.config.annotation.ResourceChainRegistration
* @see <a href="http://www.webjars.org">webjars.org</a>
*/
public class WebJarsResourceResolver extends AbstractResourceResolver {
private final static String WEBJARS_LOCATION = "META-INF/resources/webjars";
private final static int WEBJARS_LOCATION_LENGTH = WEBJARS_LOCATION.length();
private final WebJarAssetLocator webJarAssetLocator = new WebJarAssetLocator();
@Override
protected Resource resolveResourceInternal(HttpServletRequest request, String requestPath,
List<? extends Resource> locations, ResourceResolverChain chain) {
Resource resolved = chain.resolveResource(request, requestPath, locations);
if (resolved == null) {
String webJarResourcePath = findWebJarResourcePath(requestPath);
if (webJarResourcePath != null) {
return chain.resolveResource(request, webJarResourcePath, locations);
}
}
return resolved;
}
@Override
protected String resolveUrlPathInternal(String resourceUrlPath,
List<? extends Resource> locations, ResourceResolverChain chain) {
String path = chain.resolveUrlPath(resourceUrlPath, locations);
if (path == null) {
String webJarResourcePath = findWebJarResourcePath(resourceUrlPath);
if (webJarResourcePath != null) {
return chain.resolveUrlPath(webJarResourcePath, locations);
}
}
return path;
}
protected String findWebJarResourcePath(String path) {
try {
int startOffset = (path.startsWith("/") ? 1 : 0);
int endOffset = path.indexOf("/", 1);
if (endOffset != -1) {
String webjar = path.substring(startOffset, endOffset);
String partialPath = path.substring(endOffset);
String webJarPath = webJarAssetLocator.getFullPath(webjar, partialPath);
return webJarPath.substring(WEBJARS_LOCATION_LENGTH);
}
}
catch (MultipleMatchesException ex) {
if (logger.isWarnEnabled()) {
logger.warn("WebJar version conflict for \"" + path + "\"", ex);
}
}
catch (IllegalArgumentException ex) {
if (logger.isTraceEnabled()) {
logger.trace("No WebJar resource found for \"" + path + "\"");
}
}
return null;
}
}
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