/*
* Copyright 2002-2010 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.io.IOException;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.core.io.Resource;
import org.springframework.http.MediaType;
import org.springframework.util.Assert;
import org.springframework.util.FileCopyUtils;
import org.springframework.util.StringUtils;
import org.springframework.web.HttpRequestHandler;
import org.springframework.web.context.request.ServletWebRequest;
import org.springframework.web.servlet.HandlerMapping;
import org.springframework.web.servlet.support.WebContentGenerator;
/**
* {@link HttpRequestHandler} that serves static resources optimized for superior browser performance
* (according to the guidelines of Page Speed, YSlow, etc.) by allowing for flexible cache settings
* ({@link #setCacheSeconds "cacheSeconds" property}, last-modified support).
*
* <p>The {@link #setLocations "locations" property takes a list of Spring {@link Resource} locations
* from which static resources are allowed to be served by this handler. For a given request, the
* list of locations will be consulted in order for the presence of the requested resource, and the
* first found match will be written to the response, with {@code Expires} and {@code Cache-Control}
* headers set as configured. The handler also properly evaluates the {@code Last-Modified} header
* (if present) so that a {@code 304} status code will be returned as appropriate, avoiding unnecessary
* overhead for resources that are already cached by the client. The use of {@code Resource} locations
* allows resource requests to easily be mapped to locations other than the web application root. For
* example, resources could be served from a classpath location such as "classpath:/META-INF/public-web-resources/",
* allowing convenient packaging and serving of resources such as a JavaScript library from within jar files.
*
* <p>To ensure that users with a primed browser cache get the latest changes to application-specific
* resources upon deployment of new versions of the application, it is recommended that a version string
* is used in the URL mapping pattern that selects this handler. Such patterns can be easily parameterized
* using Spring EL. See the reference manual for further examples of this approach.
*
* <p>Rather than being directly configured as a bean, this handler will typically be configured
* through use of the <code><mvc:resources/></code> XML configuration element.
*
* @author Keith Donald
* @author Jeremy Grelle
* @author Juergen Hoeller
* @since 3.0.4
*/
public class ResourceHttpRequestHandler extends WebContentGenerator implements HttpRequestHandler {
private List<Resource> locations;
public ResourceHttpRequestHandler() {
super(METHOD_GET, METHOD_HEAD);
}
/**
* Set a {@code List} of {@code Resource} paths to use as sources
* for serving static resources.
*/
public void setLocations(List<Resource> locations) {
Assert.notEmpty(locations, "Location list must not be empty");
this.locations = locations;
}
/**
* Processes a resource request.
* <p>Checks for the existence of the requested resource in the configured list of locations.
* If the resource does not exist, a {@code 404} response will be returned to the client.
* If the resource exists, the request will be checked for the presence of the
* {@code Last-Modified} header, and its value will be compared against the last-modified
* timestamp of the given resource, returning a {@code 304} status code if the
* {@code Last-Modified} value is greater. If the resource is newer than the
* {@code Last-Modified} value, or the header is not present, the content resource
* of the resource will be written to the response with caching headers
* set to expire one year in the future.
*/
public void handleRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
checkAndPrepare(request, response, true);
// check whether a matching resource exists
Resource resource = getResource(request);
if (resource == null) {
logger.debug("No matching resource found - returning 404");
response.sendError(HttpServletResponse.SC_NOT_FOUND);
return;
}
// check the resource's media type
MediaType mediaType = getMediaType(resource);
if (mediaType != null) {
if (logger.isDebugEnabled()) {
logger.debug("Determined media type [" + mediaType + "] for " + resource);
}
}
else {
if (logger.isDebugEnabled()) {
logger.debug("No media type found for " + resource + " - returning 404");
}
response.sendError(HttpServletResponse.SC_NOT_FOUND);
return;
}
// header phase
setHeaders(response, resource, mediaType);
if (new ServletWebRequest(request, response).checkNotModified(resource.lastModified())) {
logger.debug("Resource not modified - returning 304");
return;
}
// content phase
if (METHOD_HEAD.equals(request.getMethod())) {
logger.trace("HEAD request - skipping content");
return;
}
writeContent(response, resource);
}
protected Resource getResource(HttpServletRequest request) {
String path = (String) request.getAttribute(HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE);
if (path == null) {
throw new IllegalStateException("Required request attribute '" +
HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE + "' is not set");
}
if (!StringUtils.hasText(path) || path.contains("WEB-INF") || path.contains("META-INF")) {
if (logger.isDebugEnabled()) {
logger.debug("Ignoring invalid resource path [" + path + "]");
}
return null;
}
for (Resource location : this.locations) {
try {
if (logger.isDebugEnabled()) {
logger.debug("Trying relative path [" + path + "] against base location: " + location);
}
Resource resource = location.createRelative(path);
if (resource.exists() && resource.isReadable()) {
if (logger.isDebugEnabled()) {
logger.debug("Found matching resource: " + resource);
}
return resource;
}
else if (logger.isTraceEnabled()) {
logger.trace("Relative resource doesn't exist or isn't readable: " + resource);
}
}
catch (IOException ex) {
logger.debug("Failed to create relative resource - trying next resource location", ex);
}
}
return null;
}
/**
* Determine an appropriate media type for the given resource.
* @param resource the resource to check
* @return the corresponding media type, or <code>null</code> if none found
*/
protected MediaType getMediaType(Resource resource) {
String mimeType = getServletContext().getMimeType(resource.getFilename());
return (StringUtils.hasText(mimeType) ? MediaType.parseMediaType(mimeType) : null);
}
/**
* Set headers on the given servlet response.
* Called for GET requests as well as HEAD requests.
* @param response current servlet response
* @param resource the identified resource (never <code>null</code>)
* @param mediaType the resource's media type (never <code>null</code>)
* @throws IOException in case of errors while setting the headers
*/
protected void setHeaders(HttpServletResponse response, Resource resource, MediaType mediaType) throws IOException {
long length = resource.contentLength();
if (length > Integer.MAX_VALUE) {
throw new IOException("Resource content too long (beyond Integer.MAX_VALUE): " + resource);
}
response.setContentLength((int) length);
response.setContentType(mediaType.toString());
}
/**
* Write the actual content out to the given servlet response,
* streaming the resource's content.
* @param response current servlet response
* @param resource the identified resource (never <code>null</code>)
* @throws IOException in case of errors while writing the content
*/
protected void writeContent(HttpServletResponse response, Resource resource) throws IOException {
FileCopyUtils.copy(resource.getInputStream(), response.getOutputStream());
}
}
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