dbconnectionpool.java

一个数据库连接池的完整代码

package eise.db;
//------------------------------------------------------------------------------
import java.util.*;
import java.sql.*;
//------------------------------------------------------------------------------
public class DBConnectionPool{
    private int checkedOut=0;//被占用的连接数目
    private Vector freeConnections;//空闲的连接
    private int maxConn;//最大的连接数
    private String name;//数据库类型的名称,如MySQL, SQL SERVER, ACCESS等
    private String password;//密码
    private String URL;//连接的地址
    private String user;//连接的用户
    private DBConnectionManager connMgr=null;
//------------------------------------------------------------------------------
    public DBConnectionPool(DBConnectionManager connMgrObj,String nameStr, String urlStr, String userStr, String passwordStr, int maxInt){
        connMgr=connMgrObj;
        freeConnections = new Vector();
        name = nameStr;
        URL = urlStr;
        user = userStr;
        password = passwordStr;
        maxConn = maxInt;
        checkedOut=0;
    }
//------------------------------------------------------------------------------
    public synchronized void freeConnection(Connection connection){
        freeConnections.addElement(connection);
        checkedOut--;
        notifyAll();
    }
//------------------------------------------------------------------------------
    public synchronized Connection getConnection(){
        Connection connection = null;
        if(freeConnections.size()>0)
           {connection = (Connection)freeConnections.firstElement();
            freeConnections.removeElementAt(0);
            try{if(connection.isClosed())
                  {connMgr.log("此连接已经关闭：" + name);
                   connection = getConnection();
                  }
                }
            catch(SQLException ee)
               {connMgr.log("取得连接时出现错误：" + name);
                connection = getConnection();
               }
           }
        else if(maxConn == 0 || checkedOut < maxConn){connection = newConnection();}
        if(connection != null){checkedOut++;}
        return connection;
    }
//------------------------------------------------------------------------------
    public synchronized Connection getConnection(long limit_long){
        long now_long = (new java.util.Date()).getTime();
        Connection connection;
        while((connection = getConnection()) == null)
            {try{wait(limit_long);}
             catch(InterruptedException ee) {connMgr.log("等待空闲的连接时出现错误：" + name);}
             if((new java.util.Date()).getTime() - now_long >= limit_long){return null;}
            }
        return connection;
    }
//------------------------------------------------------------------------------
    private Connection newConnection(){
        Connection connection = null;
        try{if(user == null){connection = DriverManager.getConnection(URL);}
            else{connection = DriverManager.getConnection(URL, user, password);}
            connMgr.log("成功建立新的连接：" + name);
           }
        catch(SQLException ee)
           {connMgr.log(ee, "建立新连接时失败: " + URL);
            return null;
           }
        return connection;
    }
//------------------------------------------------------------------------------
    public synchronized void release(){
        for(Enumeration enumeration = freeConnections.elements(); enumeration.hasMoreElements();)
           {Connection connection = (Connection)enumeration.nextElement();
            try{connection.close();
                connMgr.log("成功关闭连接：" + name);
               }
            catch(SQLException ee)
               {connMgr.log(ee, "关闭连接时失败：" + name);
               }
           }
        freeConnections.removeAllElements();
        checkedOut=0;
    }
//------------------------------------------------------------------------------
}//内部类结束
//------------------------------------------------------------------------------