001    /**
002     * Copyright (c) 2000-2010 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.io.unsync.UnsyncByteArrayOutputStream;
018    import com.liferay.portal.kernel.servlet.HttpHeaders;
019    import com.liferay.portal.kernel.servlet.StringServletResponse;
020    
021    import javax.servlet.http.HttpServletRequest;
022    import javax.servlet.http.HttpServletResponse;
023    
024    /**
025     * @author Brian Wing Shun Chan
026     * @author Shuyang Zhou
027     */
028    public class ETagUtil {
029    
030            public static boolean processETag(
031                    HttpServletRequest request, HttpServletResponse response,
032                    byte[] bytes) {
033    
034                    return _processETag(
035                            request, response, _hashCode(bytes, 0, bytes.length));
036            }
037    
038            public static boolean processETag(
039                    HttpServletRequest request, HttpServletResponse response, byte[] bytes,
040                    int length) {
041    
042                    return _processETag(request, response, _hashCode(bytes, 0, length));
043            }
044    
045            public static boolean processETag(
046                    HttpServletRequest request, HttpServletResponse response, byte[] bytes,
047                    int offset, int length) {
048    
049                    return _processETag(
050                            request, response, _hashCode(bytes, offset, length));
051            }
052    
053            public static boolean processETag(
054                    HttpServletRequest request, HttpServletResponse response, String s) {
055    
056                    return _processETag(request, response, s.hashCode());
057            }
058    
059            public static boolean processETag(
060                    HttpServletRequest request, HttpServletResponse response,
061                    StringServletResponse stringResponse) {
062    
063                    if (stringResponse.isCalledGetOutputStream()) {
064                            UnsyncByteArrayOutputStream unsyncByteArrayOutputStream =
065                                    stringResponse.getUnsyncByteArrayOutputStream();
066    
067                            return processETag(
068                                    request, response,
069                                    unsyncByteArrayOutputStream.unsafeGetByteArray(),
070                                    unsyncByteArrayOutputStream.size());
071                    }
072                    else {
073                            return processETag(request, response, stringResponse.getString());
074                    }
075            }
076    
077            private static int _hashCode(byte[] data, int offset, int length) {
078                    int hashCode = 0;
079    
080                    for (int i = 0; i < length; i++) {
081                            hashCode = 31 * hashCode + data[offset++];
082                    }
083    
084                    return hashCode;
085            }
086    
087            private static boolean _processETag(
088                    HttpServletRequest request, HttpServletResponse response,
089                    int hashCode) {
090    
091                    String eTag = Integer.toHexString(hashCode);
092    
093                    response.setHeader(HttpHeaders.ETAG, eTag);
094    
095                    String ifNoneMatch = request.getHeader(HttpHeaders.IF_NONE_MATCH);
096    
097                    if (eTag.equals(ifNoneMatch)) {
098                            response.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
099                            response.setContentLength(0);
100    
101                            return true;
102                    }
103                    else {
104                            return false;
105                    }
106            }
107    
108    }