Package com.jfinal.plugin.ehcache

Source Code of com.jfinal.plugin.ehcache.CacheInterceptor

/**
* Copyright (c) 2011-2015, James Zhan 詹波 (jfinal@126.com).
*
* 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.jfinal.plugin.ehcache;

import java.util.Enumeration;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import javax.servlet.http.HttpServletRequest;
import com.jfinal.aop.Interceptor;
import com.jfinal.core.ActionInvocation;
import com.jfinal.core.Controller;

/**
* CacheInterceptor.
*/
public class CacheInterceptor implements Interceptor {
 
  private static final String renderKey = "$renderKey$";
  private static volatile ConcurrentHashMap<String, ReentrantLock> lockMap = new ConcurrentHashMap<String, ReentrantLock>();
 
  private ReentrantLock getLock(String key) {
    ReentrantLock lock = lockMap.get(key);
    if (lock != null)
      return lock;
   
    lock = new ReentrantLock();
    ReentrantLock previousLock = lockMap.putIfAbsent(key, lock);
    return previousLock == null ? lock : previousLock;
  }
 
  final public void intercept(ActionInvocation ai) {
    Controller controller = ai.getController();
    String cacheName = buildCacheName(ai, controller);
    String cacheKey = buildCacheKey(ai, controller);
    Map<String, Object> cacheData = CacheKit.get(cacheName, cacheKey);
    if (cacheData == null) {
      Lock lock = getLock(cacheName);
      lock.lock();          // prevent cache snowslide
      try {
        cacheData = CacheKit.get(cacheName, cacheKey);
        if (cacheData == null) {
          ai.invoke();
          cacheAction(cacheName, cacheKey, controller);
          return ;
        }
      }
      finally {
        lock.unlock();
      }
    }
   
    useCacheDataAndRender(cacheData, controller);
  }
 
  // TODO 考虑与 EvictInterceptor 一样强制使用  @CacheName
  private String buildCacheName(ActionInvocation ai, Controller controller) {
    CacheName cacheName = ai.getMethod().getAnnotation(CacheName.class);
    if (cacheName != null)
      return cacheName.value();
    cacheName = controller.getClass().getAnnotation(CacheName.class);
    return (cacheName != null) ? cacheName.value() : ai.getActionKey();
  }
 
  private String buildCacheKey(ActionInvocation ai, Controller controller) {
    StringBuilder sb = new StringBuilder(ai.getActionKey());
    String urlPara = controller.getPara();
    if (urlPara != null)
      sb.append("/").append(urlPara);
   
    String queryString = controller.getRequest().getQueryString();
    if (queryString != null)
      sb.append("?").append(queryString);
    return sb.toString();
  }
 
  private void cacheAction(String cacheName, String cacheKey, Controller controller) {
    HttpServletRequest request = controller.getRequest();
    Map<String, Object> cacheData = new HashMap<String, Object>();
    for (Enumeration<String> names=request.getAttributeNames(); names.hasMoreElements();) {
      String name = names.nextElement();
      cacheData.put(name, request.getAttribute(name));
    }
   
    cacheData.put(renderKey, new RenderInfo(controller.getRender()));    // cache RenderInfo
    CacheKit.put(cacheName, cacheKey, cacheData);
  }
 
  private void useCacheDataAndRender(Map<String, Object> cacheData, Controller controller) {
    HttpServletRequest request = controller.getRequest();
    Set<Entry<String, Object>> set = cacheData.entrySet();
    for (Iterator<Entry<String, Object>> it=set.iterator(); it.hasNext();) {
      Entry<String, Object> entry = it.next();
      request.setAttribute(entry.getKey(), entry.getValue());
    }
    request.removeAttribute(renderKey);
   
    controller.render(((RenderInfo)cacheData.get(renderKey)).createRender());    // set render from cacheData
  }
}





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