以前認為連接池，線程池這些東西很高端。因為出了問題之后，總是有人說這個連接池/線程線的配置不對嘛，應該..... 今天學習了下，這個池到底應該怎么設計。發現apache的common-pool早就思考過這個問題了，并且定義了一個規范和框架?；诖宋覍W習了些資料來寫一個數據庫連接池。

先寫個測試程序，多線程不停的拿連接與釋放連接，取到連接就打印一下連接id。如果同一個id，出現多次，則證明這個連接被復用了。

1.測試程序

public class TestJDBCPool {

public static void main(String[] args) {

//初始化,實際可用spring初始化

JDBCPool pool=new JDBCPool("jdbc:mysql://localhost:3306/test","root","xx","com.mysql.jdbc.Driver",null);

try {

for (int i = 0; i < 200; i++) {

new Thread(new PoolTestThread(pool)).start();

}

} catch (Exception e) {

e.printStackTrace();

}

}

private static class PoolTestThread implements Runnable {

private JDBCPool pool;

public PoolTestThread(JDBCPool pool) {

this.pool=pool;

}

public void run() {

try {

Connection conn = pool.getConnection();

System.out.println(Thread.currentThread().getName() + " : " + conn.hashCode());

Thread.sleep(1000);

//歸還連接

JDBCPool.returnConnection(conn);

} catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

}

}

2.設計JDBCPool

根據common-pool的定義，我們要定義兩個類，一個是Pool類給應用提供"取對象"與"還對象"兩個方法。另一個是PooledObjectFactory類，用于生產對象與包裝對象。

package net.highersoft.pool;

import java.sql.Connection;

import java.sql.DriverManager;

import org.apache.commons.pool2.BasePooledObjectFactory;

import org.apache.commons.pool2.PooledObject;

import org.apache.commons.pool2.impl.DefaultPooledObject;

import org.apache.commons.pool2.impl.GenericObjectPool;

import org.apache.commons.pool2.impl.GenericObjectPoolConfig;

public class JDBCPool {

private volatile static JDBCPool pool;

private static GenericObjectPool connPool;

/**

* 初始化連接池，傳遞所需資源

* @param url

* @param userName

* @param passwd

* @param driver

* @param config

*/

public JDBCPool(String url,String userName,String passwd,String driver,GenericObjectPoolConfig config) {

if (config == null) {

config = getDefaultConfig();

}

connPool = new GenericObjectPool(new JDBCPooledFactory(url,userName,passwd,driver), config);

}

private GenericObjectPoolConfig getDefaultConfig() {

GenericObjectPoolConfig conf = new GenericObjectPoolConfig();

// TODO -- 默認8,8,0

conf.setMaxTotal(50);

conf.setMaxIdle(50);

conf.setMinIdle(0);

conf.setMaxWaitMillis(60000);

return conf;

}

/**

* 得到連接

* @return

* @throws Exception

*/

public Connection getConnection() throws Exception {

return connPool.borrowObject();

}

/**

* 釋放連接

* @param conn

*/

public static void returnConnection(Connection conn) {

connPool.returnObject(conn);

}

static class JDBCPooledFactory extends BasePooledObjectFactory {

private String url;

private String userName;

private String passwd;

public JDBCPooledFactory(String url,String userName,String passwd,String driver) {

try {

Class.forName(driver);

} catch (ClassNotFoundException e) {

e.printStackTrace();

}

this.url=url;

this.userName=userName;

this.passwd=passwd;

}

//創建對象

@Override

public Connection create() throws Exception {

return DriverManager.getConnection(url, userName, passwd);

}

//包裝對象

@Override

public PooledObject wrap(Connection conn) {

return new DefaultPooledObject(conn);

}

}

}

再看一下maven依賴:

org.apache.commons

commons-pool2

2.4.2

mysql

mysql-connector-java

5.0.5

總結

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