connpool.java

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package com.dbconn;

import java.sql.*;
import java.util.*;

public class ConnPool {

	private int connNow = 0;						//现在连接数
	private int maxConn;							//最大连接数	
	private String poolName = null;				//连接池名字
	private String driverName = null;				//驱动程序名
	private String url = null;						//连接数据库url
	private String userName = null;				//数据库用户名
	private String pwd = null;						//数据库密码
	private Vector connections = new Vector();		//存放连接的容器
	
	public ConnPool(String poolName,String driverName,String url,String userName,String pwd,int maxConn){
		
		this.poolName = poolName;
		this.driverName = driverName;
		this.url = url;
		this.userName = userName;
		this.pwd = pwd;
		this.maxConn = maxConn;
	}
	
	public synchronized void releaseConnection(Connection conn){				//释放连接（不是关闭连接）
		
		connections.addElement(conn);      
		connNow--;
		
	}
	
	public synchronized Connection getConnection(){							//获取连接（不是建立连接）
		
		Connection conn = null;
		if(connections.size() > 0){
			
			conn = (Connection)connections.elementAt(0);
			connections.removeElementAt(0);
			
			try{
				if(conn.isClosed())
					conn=getConnection();
			}
			catch(Exception e){
				e.printStackTrace();
			}			
		}
		
		else if(maxConn == 0 || connNow < maxConn){			
			conn = newConnection();
		}
		if(conn != null){
			connNow++;
		}
		return conn;
	}
	
	private Connection newConnection(){										//建立连接
		
		Connection conn = null;
		
		try{
			Class.forName(driverName);
			conn = DriverManager.getConnection(url,userName,pwd);
		}
		catch(Exception e){
			e.printStackTrace();
			return null;
		}
		
		return conn;		
	}
	
	public synchronized void closeConn(){									//关闭连接
		
		Enumeration allConnections = connections.elements();
		
		while(allConnections.hasMoreElements()){
			Connection conn = (Connection)allConnections.nextElement();
			try{
				conn.close();
			}
			catch(Exception e){
				e.printStackTrace();
			}
		}		
		connections.removeAllElements();		
	}
	
}