连接池apache-common-pool2

Posted 2021-04-06 分布式服务

Apache commons-pool2类库是对象池技术的一种具体实现，数据库连接池DBCP就是用的它。

仅记录一下如何使用，需要干货可以学习源码，具体的源码解析参见：http://blog.csdn.net/zilong_zilong/article/details/78556281

• PooledObject：池对象，封装实际对象的。定义了getCreateTime获取PooledObject创建时间，getActiveTimeMillis获取PooledObject处于激活状态的时间，getIdleTimeMillis获取PooledObject空闲时间，getLastBorrowTime获取PooledObject最近借出时间，getLastReturnTime获取PooledObject最近归还时间，getLastUsedTime获取PooledObject最近使用时间。目前Apache commons-pool2提供了2个默认实现DefaultPooledObject和PooledSoftReference，一般使用DefaultPooledObject即可

•  PooledObjectFactory：作用是生产PooledObject，定义了makeObject创建、destroyObject销毁、validateObject校验、activateObject激活PooledObject对象，使用Apache commons-pool2的使用者需要自己实现这个接口

• ObjectPool：对象池，管理池里面的PooledObject，borrowObject借出PooledObject，returnObject归还PooledObject，invalidateObject调用PooledObjectFactory销毁PooledObject，addObject调用PooledObjectFactory创建PooledObject，getNumIdle给出PooledObject空闲个数，getNumActive给出PooledObject激活的个数，使用Apache commons-pool2的使用者可以使用默认的5个实现(SoftReferenceObjectPool GenericObjectPool ProxiedObjectPool GenericKeyedObjectPool ProxiedKeyedObjectPool)，也可以自己实现

使用对象池来管理socket连接，分三步：

• 步骤一：实现自己的PooledObjectFactory

• 步骤二：创建ObjectPool对象

• 步骤三：从ObjectPool获取到PooledObject对象，进行相关业务操作 

实现自己的PooledObjectFactory

package com.ghost.pool.socket;   import java.io.IOException; import java.net.Socket;   import org.apache.commons.pool2.PooledObject; import org.apache.commons.pool2.PooledObjectFactory; import org.apache.commons.pool2.impl.DefaultPooledObject;   publicclass SocketPooledObjectFactory implements  PooledObjectFactory<Socket> {       private String hostname;     privateintport;       public SocketPooledObjectFactory(String hostname, intport) {         this.hostname = hostname;         this.port = port;     }       @Override     public PooledObject<Socket>  makeObject() throws Exception {         returnnew DefaultPooledObject<Socket>(new Socket(hostname, port));     }       @Override     publicvoid  destroyObject(PooledObject<Socket> p) throws Exception {         Socket socket = p.getObject();         if (socket != null) {             try {                 socket.close();             } catch (IOException e) {                 System.out.println("close socket failed.");                 throwe;             }             socket = null;         }     }       @Override     publicboolean  validateObject(PooledObject<Socket> p) {         Socket socket = p.getObject();         if (socket == null){             returnfalse;         }                 if (socket.isClosed()){             returnfalse;         }                 if (!socket.isConnected()){             returnfalse;         }                 returntrue;     }       @Override     publicvoid  activateObject(PooledObject<Socket> p) throws Exception {         if (p.getObject() == null){             p = new DefaultPooledObject<Socket>(new Socket(hostname, port));         }       }       @Override     publicvoid  passivateObject(PooledObject<Socket> p) throws Exception {       } }

 创建ObjectPool对象，用默认的GenericObjectPool

package com.ghost.pool;   import java.net.Socket; import java.util.NoSuchElementException;   import org.apache.commons.pool2.ObjectPool; import org.apache.commons.pool2.PooledObjectFactory; import org.apache.commons.pool2.impl.GenericObjectPool;   import com.ghost.pool.socket.SocketPooledObjectFactory;   /**  * Hello world!  *  */ publicclass App {     publicstaticvoid main( String[] args ) throws  NoSuchElementException, IllegalStateException, Exception     {      PooledObjectFactory<Socket>  factory = new SocketPooledObjectFactory("localhost",8080);      ObjectPool  pool = new GenericObjectPool(factory);      Socket  socket1 = (Socket) pool.borrowObject();      System.out.println(socket1);            Socket  socket2 = (Socket) pool.borrowObject();      System.out.println(socket2);            pool.returnObject(socket1);            Socket  socket3= (Socket) pool.borrowObject();      System.out.println(socket3);     } }

 通过pool的borrowObject可以获取对象，使用完成后归还returnObject给pool