net.sf.ehcache.constructs.web.ResponseUtil Maven / Gradle / Ivy
/**
* Copyright 2003-2009 Terracotta, Inc.
*
* 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 net.sf.ehcache.constructs.web;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* A collection of response processing utilities, which are shared between 2 or more filters
*
* @author Greg Luck
* @version $Id: ResponseUtil.java 744 2008-08-16 20:10:49Z gregluck $
*/
public final class ResponseUtil {
private static final Logger LOG = LoggerFactory.getLogger(ResponseUtil.class);
/**
* Gzipping an empty file or stream always results in a 20 byte output
* This is in java or elsewhere.
*
* On a unix system to reproduce do gzip -n empty_file. -n tells gzip to not
* include the file name. The resulting file size is 20 bytes.
*
* Therefore 20 bytes can be used indicate that the gzip byte[] will be empty when ungzipped.
*/
private static final int EMPTY_GZIPPED_CONTENT_SIZE = 20;
/**
* Utility class. No public constructor.
*/
private ResponseUtil() {
//noop
}
/**
* Checks whether a gzipped body is actually empty and should just be zero.
* When the compressedBytes is {@link #EMPTY_GZIPPED_CONTENT_SIZE} it should be zero.
*
* @param compressedBytes the gzipped response body
* @param request the client HTTP request
* @return true if the response should be 0, even if it is isn't.
*/
public static boolean shouldGzippedBodyBeZero(byte[] compressedBytes, HttpServletRequest request) {
//Check for 0 length body
if (compressedBytes.length == EMPTY_GZIPPED_CONTENT_SIZE) {
if (LOG.isDebugEnabled()) {
LOG.debug(request.getRequestURL() + " resulted in an empty response.");
}
return true;
} else {
return false;
}
}
/**
* Performs a number of checks to ensure response saneness according to the rules of RFC2616:
*
* - If the response code is {@link javax.servlet.http.HttpServletResponse#SC_NO_CONTENT} then it is illegal for the body
* to contain anything. See http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.2.5
*
- If the response code is {@link javax.servlet.http.HttpServletResponse#SC_NOT_MODIFIED} then it is illegal for the body
* to contain anything. See http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.3.5
*
*
* @param request the client HTTP request
* @param responseStatus the responseStatus
* @return true if the response should be 0, even if it is isn't.
*/
public static boolean shouldBodyBeZero(HttpServletRequest request, int responseStatus) {
//Check for NO_CONTENT
if (responseStatus == HttpServletResponse.SC_NO_CONTENT) {
if (LOG.isDebugEnabled()) {
LOG.debug(request.getRequestURL() + " resulted in a " + HttpServletResponse.SC_NO_CONTENT
+ " response. Removing message body in accordance with RFC2616.");
}
return true;
}
//Check for NOT_MODIFIED
if (responseStatus == HttpServletResponse.SC_NOT_MODIFIED) {
if (LOG.isDebugEnabled()) {
LOG.debug(request.getRequestURL() + " resulted in a " + HttpServletResponse.SC_NOT_MODIFIED
+ " response. Removing message body in accordance with RFC2616.");
}
return true;
}
return false;
}
/**
* Adds the gzip HTTP header to the response. This is need when a gzipped body is returned so that browsers can properly decompress it.
*
* @param response the response which will have a header added to it. I.e this method changes its parameter
* @throws ResponseHeadersNotModifiableException Either the response is committed or we were called using the include method
* from a {@link javax.servlet.RequestDispatcher#include(javax.servlet.ServletRequest, javax.servlet.ServletResponse)}
* method and the set set header is ignored.
*/
public static void addGzipHeader(final HttpServletResponse response) throws ResponseHeadersNotModifiableException {
response.setHeader("Content-Encoding", "gzip");
boolean containsEncoding = response.containsHeader("Content-Encoding");
if (!containsEncoding) {
throw new ResponseHeadersNotModifiableException("Failure when attempting to set "
+ "Content-Encoding: gzip");
}
}
}