001    /**
002     * Copyright (c) 2000-2011 Liferay, Inc. All rights reserved.
003     *
004     * This library is free software; you can redistribute it and/or modify it under
005     * the terms of the GNU Lesser General Public License as published by the Free
006     * Software Foundation; either version 2.1 of the License, or (at your option)
007     * any later version.
008     *
009     * This library is distributed in the hope that it will be useful, but WITHOUT
010     * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
011     * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
012     * details.
013     */
014    
015    package com.liferay.portal.servlet.filters.etag;
016    
017    import com.liferay.portal.kernel.servlet.ByteBufferServletResponse;
018    import com.liferay.portal.kernel.servlet.HttpHeaders;
019    import com.liferay.portal.kernel.util.StringPool;
020    
021    import java.nio.ByteBuffer;
022    
023    import javax.servlet.http.HttpServletRequest;
024    import javax.servlet.http.HttpServletResponse;
025    
026    /**
027     * @author Brian Wing Shun Chan
028     * @author Shuyang Zhou
029     */
030    public class ETagUtil {
031    
032            public static boolean processETag(
033                    HttpServletRequest request, HttpServletResponse response,
034                    byte[] bytes) {
035    
036                    return _processETag(
037                            request, response, _hashCode(bytes, 0, bytes.length));
038            }
039    
040            public static boolean processETag(
041                    HttpServletRequest request, HttpServletResponse response, byte[] bytes,
042                    int length) {
043    
044                    return _processETag(request, response, _hashCode(bytes, 0, length));
045            }
046    
047            public static boolean processETag(
048                    HttpServletRequest request, HttpServletResponse response, byte[] bytes,
049                    int offset, int length) {
050    
051                    return _processETag(
052                            request, response, _hashCode(bytes, offset, length));
053            }
054    
055            public static boolean processETag(
056                    HttpServletRequest request, HttpServletResponse response, String s) {
057    
058                    return _processETag(request, response, s.hashCode());
059            }
060    
061            public static boolean processETag(
062                    HttpServletRequest request, HttpServletResponse response,
063                    ByteBufferServletResponse byteBufferResponse) {
064    
065                    ByteBuffer byteBuffer = byteBufferResponse.getByteBuffer();
066    
067                    return processETag(
068                            request, response, byteBuffer.array(), byteBuffer.position(),
069                            byteBuffer.limit());
070            }
071    
072            private static int _hashCode(byte[] data, int offset, int length) {
073                    int hashCode = 0;
074    
075                    for (int i = 0; i < length; i++) {
076                            hashCode = 31 * hashCode + data[offset++];
077                    }
078    
079                    return hashCode;
080            }
081    
082            private static boolean _processETag(
083                    HttpServletRequest request, HttpServletResponse response,
084                    int hashCode) {
085    
086                    String eTag = StringPool.QUOTE.concat(
087                            Integer.toHexString(hashCode)).concat(StringPool.QUOTE);
088    
089                    response.setHeader(HttpHeaders.ETAG, eTag);
090    
091                    String ifNoneMatch = request.getHeader(HttpHeaders.IF_NONE_MATCH);
092    
093                    if (eTag.equals(ifNoneMatch)) {
094                            response.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
095                            response.setContentLength(0);
096    
097                            return true;
098                    }
099                    else {
100                            return false;
101                    }
102            }
103    
104    }