�~�程��强 — Mon, 13 Apr 2015 15:33:00 GMT

今天在看夏欣老师的《深入浅出Hibernate》的时候，觉得老师在讲数据库连接池的时候的例子很不错，使用Java动态代理实现对Connection拦截从而让应用者��用连接池的时候不�?x��)因为手贱将Connection�l�关闭了(ji��n)�Q�代码如下：(x��)

1. �q�接池接口类ConnectionPool

package com.snippnet.pool;

import java.sql.Connection;

public interface ConnectionPool

{

Connection getConnection();

boolean releaseConnection(Connection proxy, Connection connection);

}

2. �q�接池实现类DBConnectionPool

package com.snippnet.pool;

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.SQLException;

import java.util.ArrayList;

import java.util.List;

import org.apache.commons.collections.CollectionUtils;

public class DBConnectionPool implements ConnectionPool

{

private List connections;

private int size; //最大容�?span style="white-space:pre">

static {

try

{

Class.forName("com.mysql.jdbc.Driver");

} catch (ClassNotFoundException e)

{

e.printStackTrace();

}

public DBConnectionPool(int size)

{

this.size = size;

connections = new ArrayList();

}

public synchronized Connection getConnection()

{

Connection connection = null;

if (CollectionUtils.isEmpty(connections))

{

try

{

connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/jira", "root", "root");

ConnectionHandler handler = new ConnectionHandler(this, connection);

// connection = (Connection)Proxy.newProxyInstance(this.getClass().getClassLoader(), connection.getClass().getInterfaces(), (InvocationHandler) handler);

connection = handler.bind(connection);

// connections.add(connection);

} catch (SQLException e)

{

e.printStackTrace();

}

} else

{

connection = connections.get(connections.size() - 1);

connections.remove(connections.size() - 1);

}

return connection;

}

public synchronized boolean releaseConnection(Connection proxy, Connection connection)

{

boolean bool = false;

if (connections != null)

{

if (connections.size() < (this.size - 1))

{

connections.add(proxy);

bool = true;

} else

{

try

{

if (!connection.isClosed())

{

connection.close();

}

bool = true;

} catch (SQLException e)

{

bool = false;

}

return bool;

}

3. 拦截器类ConnectionHandler

package com.snippnet.pool;

import java.lang.reflect.InvocationHandler;

import java.lang.reflect.Method;

import java.lang.reflect.Proxy;

import java.sql.Connection;

import java.sql.PreparedStatement;

import java.util.Collections;

import java.util.HashMap;

import java.util.Map;

public class ConnectionHandler implements InvocationHandler

{

private ConnectionPool pool;

private Connection connection;

private Map pstPool;

public ConnectionHandler(ConnectionPool pool, Connection connection)

{

this.pool = pool;

this.connection = connection;

this.pstPool = Collections.synchronizedMap(new HashMap());

}

public Connection bind(Connection connection)

{

this.connection = connection;

return (Connection) Proxy.newProxyInstance(connection.getClass().getClassLoader()

, new Class[]{Connection.class}

, this);

}

@Override

public Object invoke(Object proxy, Method method, Object[] args)

throws Throwable

{

Object obj = null;

if ("close".equals(method.getName()))

{

// 若�ؓ(f��)close�Ҏ(gu��)��

obj = pool.releaseConnection((Connection)proxy, connection);

}

else if ("prepareStatement".equals(method.getName()))

{

if (pstPool.containsKey((String)args[0]))

{

obj = pstPool.get((String)args[0]);

} else

{

String sql = (String)args[0];

obj = connection.prepareStatement(sql);

PrepareStatementHandler handler = new PrepareStatementHandler();

obj = handler.bind((PreparedStatement)obj);

pstPool.put(sql, (PreparedStatement)obj);

}

else

{

// 不�ؓ(f��)close�Ҏ(gu��)��

obj = method.invoke(connection, args);

}

return obj;

}

4. ��试�c?br />

package com.snippnet.pool;

import java.sql.Connection;

import java.sql.PreparedStatement;

public class DynamicConnectionPoolTest

{

public static void main(String[] args) throws Exception

{

ConnectionPool pool = new DBConnectionPool(2);

Connection con = pool.getConnection();

PreparedStatement pst = con.prepareStatement("SELECT id FROM cwd_group WHERE id = ?");

System.out.println(con);

System.out.println(pst);

con.close();

Connection con1 = pool.getConnection();

System.out.println(con1);

PreparedStatement pst2 = con1.prepareStatement("SELECT id FROM cwd_group WHERE id = ?");

System.out.println(pst2);

con.close();

}

代码功能很简单，但麻雀虽小五脏俱全�?br />当Connection定w��讄��?时候，执行�l�果�Q?br />

com.mysql.jdbc.JDBC4Connection@6276e5

com.mysql.jdbc.JDBC4PreparedStatement@edeea8: SELECT id FROM cwd_group WHERE id = ** NOT SPECIFIED **

com.mysql.jdbc.JDBC4Connection@1d44ae9

com.mysql.jdbc.JDBC4PreparedStatement@823618: SELECT id FROM cwd_group WHERE id = ** NOT SPECIFIED **

从结果可以表明没有��用缓存，每次都是取最新的记录

当Connection定w��讄��?时候，执行�l�果�Q?br />

com.mysql.jdbc.JDBC4Connection@6276e5

com.mysql.jdbc.JDBC4PreparedStatement@edeea8: SELECT id FROM cwd_group WHERE id = ** NOT SPECIFIED **

com.mysql.jdbc.JDBC4Connection@6276e5

com.mysql.jdbc.JDBC4PreparedStatement@edeea8: SELECT id FROM cwd_group WHERE id = ** NOT SPECIFIED **

从结果可以表明��用了(ji��n)�~�存�Q�第二次使用的是�W�一�ơ缓存记�?/div>

�~�程��强 2015-04-13 23:33 发表评论

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