001    /**
002     * Copyright (c) 2000-2011 Liferay, Inc. All rights reserved.
003     *
004     * The contents of this file are subject to the terms of the Liferay Enterprise
005     * Subscription License ("License"). You may not use this file except in
006     * compliance with the License. You can obtain a copy of the License by
007     * contacting Liferay, Inc. See the License for the specific language governing
008     * permissions and limitations under the License, including but not limited to
009     * distribution rights of the Software.
010     *
011     *
012     *
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    import com.liferay.portal.kernel.util.StringUtil;
021    
022    import java.nio.ByteBuffer;
023    
024    import javax.servlet.http.HttpServletRequest;
025    import javax.servlet.http.HttpServletResponse;
026    
027    /**
028     * @author Brian Wing Shun Chan
029     * @author Shuyang Zhou
030     */
031    public class ETagUtil {
032    
033            public static boolean processETag(
034                    HttpServletRequest request, HttpServletResponse response,
035                    byte[] bytes) {
036    
037                    return _processETag(
038                            request, response, _hashCode(bytes, 0, bytes.length));
039            }
040    
041            public static boolean processETag(
042                    HttpServletRequest request, HttpServletResponse response, byte[] bytes,
043                    int length) {
044    
045                    return _processETag(request, response, _hashCode(bytes, 0, length));
046            }
047    
048            public static boolean processETag(
049                    HttpServletRequest request, HttpServletResponse response, byte[] bytes,
050                    int offset, int length) {
051    
052                    return _processETag(
053                            request, response, _hashCode(bytes, offset, length));
054            }
055    
056            public static boolean processETag(
057                    HttpServletRequest request, HttpServletResponse response, String s) {
058    
059                    return _processETag(request, response, s.hashCode());
060            }
061    
062            public static boolean processETag(
063                    HttpServletRequest request, HttpServletResponse response,
064                    ByteBufferServletResponse byteBufferResponse) {
065    
066                    ByteBuffer byteBuffer = byteBufferResponse.getByteBuffer();
067    
068                    return processETag(
069                            request, response, byteBuffer.array(), byteBuffer.position(),
070                            byteBuffer.limit());
071            }
072    
073            private static int _hashCode(byte[] data, int offset, int length) {
074                    int hashCode = 0;
075    
076                    for (int i = 0; i < length; i++) {
077                            hashCode = 31 * hashCode + data[offset++];
078                    }
079    
080                    return hashCode;
081            }
082    
083            private static boolean _processETag(
084                    HttpServletRequest request, HttpServletResponse response,
085                    int hashCode) {
086    
087                    String eTag = StringPool.QUOTE.concat(
088                            StringUtil.toHexString(hashCode)).concat(StringPool.QUOTE);
089    
090                    response.setHeader(HttpHeaders.ETAG, eTag);
091    
092                    String ifNoneMatch = request.getHeader(HttpHeaders.IF_NONE_MATCH);
093    
094                    if (eTag.equals(ifNoneMatch)) {
095                            response.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
096                            response.setContentLength(0);
097    
098                            return true;
099                    }
100                    else {
101                            return false;
102                    }
103            }
104    
105    }