利用Apache commons pool2构建池应用

原文链接： http://blog.csdn.net/ouyang111222/article/details/50949556

commons pool2与commons pool1还是有很大的差别的，本文主要记录利用commons pool2构建自己的池应用。

1 依赖的引入

<dependency> <groupId>org.apache.commons</groupId> <artifactId>commons-pool2</artifactId> <version>2.4.2</version> <type>jar</type> <scope>compile</scope> </dependency> 1234567 1234567

2 构建自己的池应用

ps:本文构建一个string池，从池获取string对象  2.1 构建自己的PooledObjectFactory

PooledObjectFactory是一个池化对象工厂接口，定义了生成对象、激活对象、钝化对象、销毁对象的方法，其方法如下：

public interface PooledObjectFactory<T> { /** * 生成对象 */ PooledObject<T> makeObject() throws Exception; /** * 销毁对象 */ void destroyObject(PooledObject<T> p) throws Exception; /** * 验证对象 */ boolean validateObject(PooledObject<T> p); /** * 激活对象 */ void activateObject(PooledObject<T> p) throws Exception; /** * 钝化对象 */ void passivateObject(PooledObject<T> p) throws Exception; } 123456789101112131415161718192021222324252627 123456789101112131415161718192021222324252627

如果需要使用Commons-Pool构建构建自己的池应用，那么就需要提供一个PooledObjectFactory接口的具体实现。当然也可以继承BasePooledObjectFactory这个抽象类。本文实现PooledObjectFactory接口，如下所示：

public class StringFactory implements PooledObjectFactory<String>{ public StringFactory(){ System.out.println("init string factory.."); } public void activateObject(PooledObject<String> pool) throws Exception { // TODO Auto-generated method stub } public void destroyObject(PooledObject<String> pool) throws Exception { String str = pool.getObject(); if(str!=null){ str=null; System.out.println(str+" destroy..."); } } public PooledObject<String> makeObject() throws Exception { String i = UUID.randomUUID().toString(); System.out.println("make "+i+" success..."); return new DefaultPooledObject<String>(i); } public void passivateObject(PooledObject<String> pool) throws Exception { // TODO Auto-generated method stub } public boolean validateObject(PooledObject<String> pool) { // TODO Auto-generated method stub return false; } } 1234567891011121314151617181920212223242526272829303132333435 1234567891011121314151617181920212223242526272829303132333435

2.2 创建对象池

在org.apache.commons.pool2.impl中有三个可以直接使用的对象池：GenericObjectPool、GenericKeyedObjectPool和SoftReferenceObjectPool。

通常使用GenericObjectPool来创建对象池，如果是对象池是Keyed的，那么可以使用GenericKeyedObjectPool来创建对象池。

而SoftReferenceObjectPool对象池，它利用一个Java.util.ArrayList对象来保存对象池里的对象。不过它并不在对象池里直接保存对象本身，而是保存它们的“软引用”。  （1）GenericObjectPool的使用  如下所示为GenericObjectPool的使用：

GenericObjectPoolConfig conf = new GenericObjectPoolConfig(); conf.setMaxTotal(10); GenericObjectPool<String> pool = new GenericObjectPool<String>(new StringFactory(), conf); for(int i=0;i<15;i++){ System.out.println(i+":"); try { String str = pool.borrowObject(); System.out.println(str); } catch (Exception e) { e.printStackTrace(); } } 123456789101112 123456789101112

上例中设置GenericObjectPool的maxTotal为10，开启一个循环（循环次数为15），每次从池中拿一个对象，由于池的大小为10，每次拿到对象之后没有释放，所以程序block在i=10处。    下面的例子为每次拿到对象之后，处理完再释放：

GenericObjectPoolConfig conf = new GenericObjectPoolConfig(); conf.setMaxTotal(10); GenericObjectPool<String> pool = new GenericObjectPool<String>(new StringFactory(), conf); for(int i=0;i<15;i++){ System.out.println(i+":"); try { String str = pool.borrowObject(); System.out.println(str); pool.returnObject(str); } catch (Exception e) { e.printStackTrace(); } } 12345678910111213 12345678910111213

其运行结果如下： 

（2）自定义pool  如下所示为自定义Pool实现了Closeable接口，定义自己的获取资源与释放资源的方法。

public class Pool implements Closeable{ public GenericObjectPool<String> innerPool; public Pool() { } public Pool(final GenericObjectPoolConfig poolConfig,PooledObjectFactory<String> factory){ initPool(poolConfig, factory); } public void close() throws IOException { innerPool.close(); } public void initPool(final GenericObjectPoolConfig poolConfig,PooledObjectFactory<String> factory){ if(this.innerPool!=null){ System.out.println("innerPool is not null,destroy it.."); innerPool.close(); } this.innerPool = new GenericObjectPool<String>(factory,poolConfig); } public String getResource(){ String str = ""; try { str=this.innerPool.borrowObject(); System.out.println("get resource success..:"+str); } catch (Exception e) { e.printStackTrace(); System.out.println("get resource error..."); }finally{ return str; } } public void returnResourceObject(final String resource){ if(resource==null){ return; } innerPool.returnObject(resource); System.out.println("return resource success.."+resource); } } 123456789101112131415161718192021222324252627282930313233343536373839404142434445 123456789101112131415161718192021222324252627282930313233343536373839404142434445

其StringPool继承Pool就可以了：

public class StringPool extends Pool{ public StringPool(){ } public StringPool(final GenericObjectPoolConfig poolConfig,StringFactory factory){ super(poolConfig,factory); } } 123456789 123456789

如下为获取资源的实例：

GenericObjectPoolConfig poolConfig = new GenericObjectPoolConfig (); poolConfig.setMaxTotal(10); StringFactory factory = new StringFactory(); StringPool pool = new StringPool(poolConfig,factory); for(int i=0;i<15;i++){ System.out.println(i+":"); String str = pool.getResource(); System.out.println(str); } try { pool.close(); } catch (IOException e) { e.printStackTrace(); } 1234567891011121314 1234567891011121314

其运行结果如下： 

测试一下释放资源的方法：

GenericObjectPoolConfig poolConfig = new GenericObjectPoolConfig (); poolConfig.setMaxTotal(10); StringFactory factory = new StringFactory(); StringPool pool = new StringPool(poolConfig,factory); for(int i=0;i<15;i++){ System.out.println(i+":"); String str = pool.getResource(); System.out.println(str); pool.returnResourceObject(str); } try { pool.close(); } catch (IOException e) { e.printStackTrace(); } 123456789101112131415 123456789101112131415

其运行结果如下：