AbCacheHeaderParser.java

/*
 * Copyright (C) 2012 www.amsoft.cn
 * 
 * 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 com.ab.cache;



import java.util.Map;

import org.apache.http.impl.cookie.DateUtils;

// TODO: Auto-generated Javadoc
/**
 * 
 * © 2012 amsoft.cn
 * 名称：AbCacheHeaderParser.java 
 * 描述：缓存解析
 * @author 还如一梦中
 * @date 2015年4月3日 上午10:01:54
 * @version v1.0
 */
public class AbCacheHeaderParser {
	
    
    /**
     * 
     * 将响应解析成缓存实体.
     * @param response
     * @param force  强制缓存
     * @return
     */
    public static AbDiskCache.Entry parseCacheHeaders(AbCacheResponse response,long cacheMaxAge) {
           
    	   //{andbase=HTTP/1.1 200 OK, ETag="620e0d-dae-4f5d6331a2300", Date=Fri, 26 Jun 2015 02:17:54 GMT, 
    	   //Content-Length=3502, Last-Modified=Sun, 30 Mar 2014 17:23:56 GMT, X-Android-Received-Millis=1435285072907, 
    	   //Keep-Alive=timeout=15, max=100, Content-Type=image/png, Connection=Keep-Alive, Accept-Ranges=bytes, 
    	   //Server=Apache, Cache-Control=max-age=600000, X-Android-Sent-Millis=1435285072809}
           Map<String, String> headers = response.headers;

           long serverTimeMillis = 0;
           long expiredTimeMillis = 0;
           long maxAge = 0;
           boolean hasCacheControl = false;
           String serverEtag = null;
           String headerValue;

           //获取响应的内容的时间
           headerValue = headers.get("Date");
           if (headerValue != null) {
        	   try {
				   serverTimeMillis = DateUtils.parseDate(headerValue).getTime();
			   } catch (Exception e) {
				   e.printStackTrace();
			   }
           }
           
           //服务器的时间可能小雨当前时间，会导致始终过期
           if(serverTimeMillis == 0  || serverTimeMillis < System.currentTimeMillis()){
        	   serverTimeMillis = System.currentTimeMillis();
           }
           
           //Cache-Control有值才使用缓存超时的设置
           headerValue = headers.get("Cache-Control");
           if (headerValue != null) {
               hasCacheControl = true;
               String[] tokens = headerValue.split(",");
               for (int i = 0; i < tokens.length; i++) {
                   String token = tokens[i].trim();
                   if (token.equals("no-cache") || token.equals("no-store")) {
                	   break;
                   } else if (token.startsWith("max-age=")) {
                       try {
                           maxAge = Long.parseLong(token.substring(8));
                       } catch (Exception e) {
                       }
                   } else if (token.equals("must-revalidate") || token.equals("proxy-revalidate")) {
                       maxAge = 0;
                   }
               }
           }
           
           //服务端未设置Header缓存，才使用app的设置
           if(maxAge==0 && cacheMaxAge > 0){
        	   hasCacheControl = true;
        	   maxAge = cacheMaxAge;
    	   }
           
           serverEtag = headers.get("ETag");

           if (hasCacheControl) {
        	   expiredTimeMillis = serverTimeMillis + maxAge;
           }

           
          
           AbDiskCache.Entry entry = new AbDiskCache.Entry();
           entry.data = response.data;
           entry.etag = serverEtag;
           entry.serverTimeMillis = serverTimeMillis;
           entry.expiredTimeMillis = expiredTimeMillis;
           entry.responseHeaders = headers;

           return entry;
           
    }
   
}