java 数据库连接池的实现代码

}
static private DBConnectionManager instance; // 唯一实例
static private int clients; //
private Vector drivers = new Vector();
java 数据库连接池的实现代码
Java代码
package com.xiaobian;
/**
* 数据库连接池管理类
*/
import java.io.*;
import java.sql.*;
import java.util.*;
import java.util.Date;
try {
DriverManager.deregisterDriver(driver);
log("撤销JDBC驱动程序 " + driver.getClass().getName() + "的注册");
if (pool != null) {
pool.freeConnection(con);
}
}
/**
* 获得一个可用的(空闲的)连接.如果没有可用连接,且已有连接数小于最大连接数 限制,则创建并返回新连接
} catch (SQLException e) {
log(e, "无法撤销下列JDBC驱动程序的注册: " + driver.getClass().getNam接对象
*/
public void freeConnection(String name, Connection con) {
DBConnectionPool pool = (DBConnectionPool) pools.get(name);
Enumeration propNames = props.propertyNames();
while (propNames.hasMoreElements()) {
String name = (String) propNames.nextElement();
}
clients++;
return instance;
}
/**
* 建构私有函数以防止其它对象创建本类实例
*/
private DBConnectionManager() {
// 等待直到最后一个客户程序调用
if (--clients != 0) {
return;
}
Enumeration allPools = pools.elements();
/**
* 管理类DBConnectionManager支持对一个或多个由属性文件定义的数据库连接池的
* 访问.客户程序可以调用getInstance()方法访问本类的唯一实例
*/
public class DBConnectionManager {
public static void main(String[] args) {
DBConnectionManager connectionManager = DBConnectionManager.getInstance();
Connection conn = connectionManager.getConnection("idb");
}
/**
* 根据指定属性创建连接池实例.
*
* @param props
* 连接池属性
*/
private void createPools(Properties props) {
DBConnectionPool pool = (DBConnectionPool) pools.get(name);
//System.out.println(" pool == "+pool);
if (pool != null) {
init();
}
/**
* 将连接对象返回给由名字指定的连接池
*
* @param name
* 在属性文件中定义的连接池名字
* @param con
Connection conn3 = connectionManager.getConnection("idb");
Connection conn4 = connectionManager.getConnection("idb");
Connection conn5 = connectionManager.getConnection("idb");
*
* @param name
* 在属性文件中定义的连接池名字
* @return Connection 可用连接或null
*/
public Connection getConnection(String name) {
}
Enumeration allDrivers = drivers.elements();
while (allDrivers.hasMoreElements()) {
Driver driver = (Driver) allDrivers.nextElement();
return pool.getConnection();
}
return null;
}
/**
* 获得一个可用连接.若没有可用连接,且已有连接数小于最大连接数限制, 则创建并返回新连接.否则,在指定的时间内等待其它线程释放连接.
Connection conn6 = connectionManager.getConnection("idb");
Connection conn7 = connectionManager.getConnection("idb");
System.out.println(" conn6 == "+conn6 +" conn7 == "+conn7);
return pool.getConnection(time);
}
return null;
}
/**
* 关闭所有连接,撤销驱动程序的注册
*/
public synchronized void release() {
connectionManager.freeConnection("idb", conn);
connectionManager.freeConnection("idb", conn1);
connectionManager.freeConnection("idb", conn2);
*
* @param name
* 连接池名字
* @param time
* 以毫秒计的等待时间
* @return Connection 可用连接或null
*/
*/
static synchronized public DBConnectionManager getInstance() {
if (instance == null) {
instance = new DBConnectionManager();
connectionManager.freeConnection("idb", conn3);
connectionManager.freeConnection("idb", conn4);
connectionManager.freeConnection("idb", conn5);
private PrintWriter log;
private Hashtable pools = new Hashtable();
/**
* 返回唯一实例.如果是第一次调用此方法,则创建实例
*
* @return DBConnectionManager 唯一实例
while (allPools.hasMoreElements()) {
DBConnectionPool pool = (DBConnectionPool) allPools.nextElement();
pool.release();
e.printStackTrace();
}
Connection conn1 = connectionManager.getConnection("idb");
Connection conn2 = connectionManager.getConnection("idb");
public Connection getConnection(String name, long time) {
DBConnectionPool pool = (DBConnectionPool) pools.get(name);
if (pool != null) {
try {
Thread.sleep(10);
} catch (InterruptedException e) {
// TODO Auto-generated catch block