handlerobjectfactory.java

一个非常好的FRAMWRK!是一个外国组织做的!不!

/*
 * Copyright 2003-2005 the original author or authors.
 * 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.model.handler;

import java.util.Collections;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.Map;

import com.jdon.model.ModelHandler;
import com.jdon.model.config.ModelXmlConfig;
import com.jdon.util.Debug;

/**
 * @author <a href="mailto:[e-mail]">banq</a>
 *
 */
public class HandlerObjectFactory {
    public final static String module = HandlerObjectFactory.class.getName();
    
    private final static int HANDLER_INSTANCE_COUNT = 10;
    
    private ModelXmlConfig modelXmlConfig;
    
    //空闲ModelHandler池
    private Map handlerFreePool = Collections.synchronizedMap(new HashMap());
    //在使用的ModelHandler池
    private Map handlerUsedPool = Collections.synchronizedMap(new HashMap());


    public HandlerObjectFactory(ModelXmlConfig modelXmlConfig) {
        super();
        this.modelXmlConfig = modelXmlConfig;
    }
    

    /**
     * 获得一个空闲的ModelHandler
     * 如果空闲池没有，就重新生成指定个数的ModelHandler实例。
     * 获得成功，则记入在用池。
     * 当客户端调用完毕，调用returnHandlerObject返回该ModelHandler实例备重用。
     * @param formName
     * @return
     * @throws java.lang.Exception
     */
    public  ModelHandler borrowHandlerObject(String formName){

      ModelHandler modelHandler = null;
      try {
        String poolKey = (modelXmlConfig.getModelMapping(formName)).getHandler();

          LinkedList listFree = (LinkedList) handlerFreePool.get(poolKey);
          if ( (listFree == null) || (listFree.isEmpty())) { //如果空了，生产
            listFree = makeHandlerObjects(formName);
            handlerFreePool.put(poolKey, listFree);
          }
          modelHandler = (ModelHandler) listFree.removeFirst();

          //加入已经用的池
          LinkedList listUsed = (LinkedList) handlerUsedPool.get(poolKey);
          if (listUsed == null) {
            listUsed = new LinkedList();
            handlerUsedPool.put(poolKey, listUsed);
          }
          listUsed.add(modelHandler);

          Debug.logVerbose("--> borrow Modelhandler instance " + poolKey +
                           listFree.size() + " for " + formName, module);
    } catch (Exception e) {
        Debug.logError("borrowHandlerObject error:" + e, module);
    }

      return modelHandler;
    }

    /**
     * 生成指定个数的实例
     * @param formName
     * @return
     * @throws java.lang.Exception
     */
    private  synchronized LinkedList makeHandlerObjects(String formName) throws Exception {
      Debug.logVerbose("--> create Modelhandler instance " +
                       HANDLER_INSTANCE_COUNT, module);
      int count = 0;
      ModelHandler modelHandler = null;
      LinkedList list = new LinkedList();
      while (count < HANDLER_INSTANCE_COUNT) {
        modelHandler = makeHandlerObject(formName);
        list.add(modelHandler);
        count++;
      }
      return list;
    }

    /**
     * 返还使用过的ModelHandler
     * 1.从使用池中删除该实例
     * 2.将该实例加入空闲池
     * @param modelHandler
     * @throws java.lang.Exception
     */
    public void returnHandlerObject(ModelHandler modelHandler) {
      try {
        String poolKey = modelHandler.getClass().getName();
          LinkedList listUsed = (LinkedList) handlerUsedPool.get(poolKey);
          if (listUsed == null) {
            Debug.logError("ERROR:not find the used pool: class = " + poolKey, module);
            return;
          }
          listUsed.remove(modelHandler);
          LinkedList listFree = (LinkedList) handlerFreePool.get(poolKey);
          if (listFree == null) {
            Debug.logError("ERROR:not find the free pool: class = " + poolKey, module);
            return;
          }
          listFree.add(modelHandler);
          Debug.logVerbose("--> return Modelhandler instance successfully" + poolKey +
                           listFree.size(), module);
    } catch (Exception e) {
        Debug.logError("returnHandlerObject error:" + e, module);
    }
    }
    

    private synchronized ModelHandler makeHandlerObject(String formName) throws Exception {
      ModelHandler object = null;
      Class handlerClass = null;
      try {
        handlerClass = (Class) modelXmlConfig.getHandlerClasses().get(formName);
        if (handlerClass == null) {
          throw new Exception(
              " not found the handler in config xml formName=" + formName);
        }
        object = (ModelHandler) handlerClass.newInstance();
      } catch (Exception e) {
        Debug.logError("--> call Handler: " + handlerClass + " error:" + e,
                       module);
        throw new Exception(e);
      }
      return object;
    }
    
    
    
}