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
*/
@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<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 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 1446015368860
java.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)
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