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
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
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* <p/>* 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 <wangjuntytl@163.com>* @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* <p/>* 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* <p/>* 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* <p/>* 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 <wangjuntytl@163.com>* @version 1.0 15/10/28* @since 1.6*/public class ConnFactory extends BasePooledObjectFactory<Conn> {/*** 间接实现{@link PooledObjectFactory#makeObject()}方法，表明怎样创建需要管理对象*/@Overridepublic 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*/@Overridepublic PooledObject<Conn> wrap(Conn obj) {return new DefaultPooledObject<Conn>(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* <p/>* {@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 <wangjuntytl@163.com>* @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* <p/>* Conn对象管理池，这里利用GenericObjectPool作为对象池** @author WangJun <wangjuntytl@163.com>* @version 1.0 15/10/28* @since 1.6*/public class ConnPool extends GenericObjectPool<Conn> {/*** 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 invalidtry {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 1446015368860
java.lang.IllegalStateException: Object has already been retured to this pool or is invalidat 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)
