httpsessionproxyvisitor.java

Java/J2EE框架Jdon-Framework系统的Sample

/**
 * Copyright 2005 Jdon.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.jdon.bussinessproxy.cache;

import com.jdon.bussinessproxy.TargetMetaDef;
import com.jdon.util.Debug;
import javax.servlet.http.HttpSessionBindingListener;
import javax.servlet.http.HttpSessionBindingEvent;
import java.util.Map;
import java.util.HashMap;
import java.util.Iterator;
import javax.ejb.EJBLocalObject;
import javax.ejb.EJBObject;


/**
 * 管理和提供与HttSession相关组件的访问，缓存这些组件为了加速性能。
 *
 HttpSessionBindingListener：
    每当往Session中存入一个对象（setAttribute）或从Session中删除一个对象的时候
   （包括容器自动删除这个Session时），
    如果这个对象实现了此监听器接口，应用服务器将会自动调用接口相应的方法：
    valueBound和valueUnbound
 HttpSessionBindingListener与HttpSessionListener区别是
 前者无需web.xml设置
 *
 * <p>Copyright: Jdon.com Copyright (c) 2005</p>
 * <p></p>
 * @author banq
 * @version JdonFramework 2005 v1.0
 */
public class HttpSessionProxyVisitor implements ComponentCacheVisitor, HttpSessionBindingListener{
  private final static String module = HttpSessionProxyVisitor.class.getName();

  private Map componentsboxs = new HashMap();

  private VisitableFactory visitableFactory;
  public HttpSessionProxyVisitor(VisitableFactory visitableFactory){
      this.visitableFactory = visitableFactory;
  }

  public void valueBound(HttpSessionBindingEvent event) {
    Debug.logVerbose(" valueBound active, sessionId :" + event.getSession().getId() , module);
    Debug.logVerbose(" valueBound active, componentsboxs size:" + componentsboxs.size() , module);
  }

  /**
   * session destroyed.
   * 去除有状态Session Bean之类的有状态引用。
   */
  public void valueUnbound(HttpSessionBindingEvent event) {
     String sessionId = event.getSession().getId();
     Debug.logVerbose(" unvalueBound active, sessionId :" + sessionId , module);
     Debug.logVerbose(" unvalueUnbound active, componentsboxs size" + componentsboxs.size(), module);
     removeObjects();
  }

  public Object visit(TargetMetaDef targetMetaDef){
    StringBuffer sb = new StringBuffer(targetMetaDef.getCacheKey());
    sb.append(targetMetaDef.getVisitableName());
    Debug.logVerbose(" visit key is " + sb.toString(), module);
    Object o = componentsboxs.get(sb.toString());
    if (o == null){
      Visitable vo = visitableFactory.createVisitable(targetMetaDef);
      o = vo.accept(this);
      componentsboxs.put(sb.toString(), o);
    }else{
      Debug.logVerbose(" got the component from session ", module);
    }
    return o;
  }


  /**
   * 需要将一些对象引用去除
   */
  public  void removeObjects(){
     try {
       Iterator iter = componentsboxs.keySet().iterator();
       while (iter.hasNext()) {
         String key = (String) iter.next();
         Object ccEjb = (Object) componentsboxs.get(key);
         removeEJBObject(key);
       }
     } catch (Exception ex) {
       Debug.logWarning(ex, module);
     } finally {
       componentsboxs.clear();
     }
    }

    /**
     * destroy the EJB.
     */
    private void removeEJBObject(Object ccEjb) {
      try {
        //这个EJB的remove方法需要被任何角色访问，因为此时principle为空
        if (ccEjb instanceof EJBLocalObject) {
          if (ccEjb != null) {
            EJBLocalObject eo = ( (EJBLocalObject) ccEjb);
            eo.remove();
          }
        } else if (ccEjb instanceof EJBObject) {
          if (ccEjb != null) {
            EJBObject eo = ( (EJBObject) ccEjb);
            eo.remove();
          }
        }
      } catch (Exception re) {

      }
    }



}