common-pool2 使用

common-pool2提供了3中对象池管理方式，它们的使用方式基本一样，这里以GenericObjectPool对象池为例介绍其使用方式，一般实现自己的对象池需要经过2个步骤

1. 实现PooledObjectFactory接口:该接口是一种工厂模式，实现其目的是让对象池通过该工厂模式创建管理的对象

2. 创建对象池(GenericObjectPool(PooledObjectFactory))实例

创建Conn对象池

我们假设Conn对象是一个建立TCP连接的对象，该对象的初始化时间平均为500ms，为了避免在程序中频繁创建Conn对象，我们需要借助对象池管理Conn对象实例

import org.slf4j.LoggerFactory;/** * common-pool2 使用方式 * 
 * 假设这是一个建立TCP连接的对象，该对象的初始化时间平均为500ms，为了避免在程序中频繁创建Conn对象，我们需要借助对象池管理Conn对象实例 * * @author WangJun 
    
      * @version 1.0 15/10/28 * @since 1.6 */public class Conn {    /**     * 记录对象的创建时间     */    private long createTime;    /**     * 初始化Conn对象，模拟创建Conn对象平均消耗500ms     * @throws InterruptedException     */    public Conn() throws InterruptedException {        Thread.sleep(500);        createTime = System.currentTimeMillis();        LoggerFactory.getLogger(getClass()).debug(" init conn suc... " + createTime);    }    /**     * 报告Conn对象信息     */    public void report() {        LoggerFactory.getLogger(getClass()).info("this is a available conn " + createTime);    }}
    

利用工厂模式，使对象池通过该工厂模式创建管理的对象

package com.peaceful.pool.demo;        import org.apache.commons.pool2.BasePooledObjectFactory;    import org.apache.commons.pool2.PooledObject;    import org.apache.commons.pool2.PooledObjectFactory;    import org.apache.commons.pool2.impl.DefaultPooledObject;        /**     * common-pool2 使用方式     * 
     * 为了使用common-pool2对象池管理，我们必须实现{@link org.apache.commons.pool2.PooledObjectFactory}或者其子类     * 这是一个工厂模式，告诉对象池怎样去创建要管理的对象     * 
     * BasePooledObjectFactory 是对{@link org.apache.commons.pool2.PooledObjectFactory}的一个基本实现，我们可以继承该类，减少一些方法的实现     * 
     * 在实现{@link org.apache.commons.pool2.PooledObjectFactory}接口时，我们一定要实现的接口方法是{@link PooledObjectFactory#makeObject()}方法。     *     * @author WangJun 
    
          * @version 1.0 15/10/28     * @since 1.6     */        public class ConnFactory extends BasePooledObjectFactory
     
       {                /**         * 间接实现{@link PooledObjectFactory#makeObject()}方法，表明怎样创建需要管理对象         */        @Override        public Conn create() throws Exception {            return new Conn();        }                /**         * 在common-pool2中为了统计管理的对象的一些信息，比如调用次数，空闲时间，上次使用时间等，需要对管理的对象进行包装，然后在放入到对象池中         *         * @param obj 对象池要管理的对象         * @return 返回包装后的PooledObject对象         */        @Override        public PooledObject
      
        wrap(Conn obj) {            return new DefaultPooledObject
       
        (obj);        }        }
       
      
     
    

为了模拟的更真实，ConnPool池可以让使用者个性化配置

package com.peaceful.pool.demo;        import org.apache.commons.pool2.impl.GenericObjectPoolConfig;        /**     * common-pool2 使用方式     * 
     * {@link org.apache.commons.pool2.impl.GenericObjectPool}支持个性化配置，我们可以配置对象池中总共的对象数，最大、最小空闲对象数等等     * 这边继承{@link GenericObjectPoolConfig}是为了ConnPool也可以进行个性化的配置     *     * @author WangJun 
    
          * @version 1.0 15/10/28     * @since 1.6     */        public class ConnPoolConfig extends GenericObjectPoolConfig {            public ConnPoolConfig() {            // defaults to make your life with connection pool easier :)            setMinIdle(5);            setTestOnBorrow(true);        }        }
    

有了创建对象的工厂，我们就可以创建一个对象池实例

package com.peaceful.pool.demo;        import org.apache.commons.pool2.impl.GenericObjectPool;        /**     * common-pool2 使用方式     * 
     * Conn对象管理池，这里利用GenericObjectPool作为对象池     *     * @author WangJun 
    
          * @version 1.0 15/10/28     * @since 1.6     */        public class ConnPool extends GenericObjectPool
     
       {                /**         * 调用{@link GenericObjectPool}的构造方法，构造ConnPool         */        public ConnPool() {            super(new ConnFactory(), new ConnPoolConfig());        }            /**         * 调用{@link GenericObjectPool}的构造方法，构造ConnPool         */        public ConnPool(ConnPoolConfig connPoolConfig) {            super(new ConnFactory(), connPoolConfig);        }        }
     
    

这样一个就完成了整个ConnPool的编码，下面我们在写一个demo，演示使用ConnPool

public class ConnDemo {            public static void main(String[] args) throws Exception {            ConnPoolConfig connPoolConfig = new ConnPoolConfig();            connPoolConfig.setMinIdle(5);            connPoolConfig.setMaxIdle(8);            ConnPool connPool = new ConnPool(connPoolConfig);            Conn conn1 = connPool.borrowObject();            Conn conn2 = connPool.borrowObject();            Conn conn3 = connPool.borrowObject();            Conn conn4 = connPool.borrowObject();            Conn conn5 = connPool.borrowObject();            conn1.report();            connPool.returnObject(conn1);            conn2.report();            connPool.returnObject(conn2);            conn3.report();            connPool.returnObject(conn3);            conn4.report();            connPool.returnObject(conn4);            conn5.report();            connPool.returnObject(conn5);                conn5.report();                // 被归还的对象的引用，不可以在次归还            // java.lang.IllegalStateException: Object has already been retured to this pool or is invalid            try {                connPool.returnObject(conn5);            }catch (Exception e){                e.printStackTrace();            }        }    }

下面是ConnDemo的运行结果

[2015-10-28 14:56:06 DEBUG]  {com.peaceful.pool.demo.Conn:18}- init conn suc...[2015-10-28 14:56:07 DEBUG]  {com.peaceful.pool.demo.Conn:18}- init conn suc...[2015-10-28 14:56:07 DEBUG]  {com.peaceful.pool.demo.Conn:18}- init conn suc...[2015-10-28 14:56:08 DEBUG]  {com.peaceful.pool.demo.Conn:18}- init conn suc...[2015-10-28 14:56:08 DEBUG]  {com.peaceful.pool.demo.Conn:18}- init conn suc...[2015-10-28 14:56:08 INFO ]  {com.peaceful.pool.demo.Conn:22}-this is a available conn 1446015366746[2015-10-28 14:56:08 INFO ]  {com.peaceful.pool.demo.Conn:22}-this is a available conn 1446015367346[2015-10-28 14:56:08 INFO ]  {com.peaceful.pool.demo.Conn:22}-this is a available conn 1446015367853[2015-10-28 14:56:08 INFO ]  {com.peaceful.pool.demo.Conn:22}-this is a available conn 1446015368354[2015-10-28 14:56:08 INFO ]  {com.peaceful.pool.demo.Conn:22}-this is a available conn 1446015368860[2015-10-28 14:56:08 INFO ]  {com.peaceful.pool.demo.Conn:22}-this is a available conn 1446015368860java.lang.IllegalStateException: Object has already been retured to this pool or is invalid    at org.apache.commons.pool2.impl.GenericObjectPool.returnObject(GenericObjectPool.java:595)    at com.peaceful.pool.demo.ConnDemo.main(ConnDemo.java:37)    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)    at java.lang.reflect.Method.invoke(Method.java:606)    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:140)