package com.systop.chinamobile.dao;
/**
* 数据库连接池中方法的具体的实现
*
* author wushichao
*
* 2008.9.24
*/
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Date;
import java.util.Enumeration;
import java.util.Vector;
// 连接池文件
public class DBConnectionPool {
private int checkedOut;//
private Vector freeConnections = new Vector();// 存储连接的对象
private int maxConn;// 最大的连接数
private int normalConn;// 保持的连接数
private String password;// 密码
private String url;// 连接字符串
private String user;// 用户名
private static int num = 0;// 空闲的连接数
private static int numActive = 0;// 当前的连接数
// 构造函数
public DBConnectionPool(String password, String url, String user,
int normalConn, int maxConn) {
this.password = password;
this.url = url;
this.user = user;
this.maxConn = maxConn;
this.normalConn = normalConn;
for (int i = 0; i < normalConn; i++) { // 初始normalConn个连接
Connection c = newConnection();
if (c != null) {
freeConnections.addElement(c);
num++;
}
}
}
// 释放不用的连接到连接池
public synchronized void freeConnection(Connection con) {
freeConnections.addElement(con);
num++;
checkedOut--;
numActive--;
notifyAll();
}
// 获取一个可用连接
public synchronized Connection getConnection() {
Connection con = null;
if (freeConnections.size() > 0) { // 还有空闲的连接
num--;
con = (Connection) freeConnections.firstElement();
freeConnections.removeElementAt(0);
try {
if (con.isClosed()) {
System.out.println("从连接池删除一个无效连接");
con = getConnection();
}
} catch (SQLException e) {
System.out.println("从连接池删除一个无效连接");
con = getConnection();
}
}
else if (maxConn == 0 || checkedOut < maxConn) { // 没有空闲连接且当前连接小于最大允许值,最大值为0则不限制
con = newConnection();
}
if (con != null) { // 当前连接数加1
checkedOut++;
}
numActive++;
return con;
}
// 获取一个连接,并加上等待时间限制,时间为毫秒
public synchronized Connection getConnection(long timeout) {
long startTime = new Date().getTime();
Connection con;
while ((con = getConnection()) == null) {
try {
wait(timeout);
} catch (InterruptedException e) {
}
if ((new Date().getTime() - startTime) >= timeout) {
return null; // 超时返回
}
}
return con;
}
// 关闭所有连接
public synchronized void release() {
Enumeration allConnections = freeConnections.elements();
while (allConnections.hasMoreElements()) {
Connection con = (Connection) allConnections.nextElement();
try {
con.close();
num--;
} catch (SQLException e) {
System.out.println("无法关闭连接池中的连接");
}
}
freeConnections.removeAllElements();
numActive = 0;
}
// 创建一个新连接
private Connection newConnection() {
Connection con = null;
try {
if (user == null) { // 用户,密码都为空
con = DriverManager.getConnection(url);
} else {
con = DriverManager.getConnection(url, user, password);
}
System.out.println("连接池创建一个新的连接");
} catch (SQLException e) {
System.out.println("无法创建这个URL的连接" + url);
return null;
}
return con;
}
// 返回当前空闲连接数
public int getnum() {
return num;
}
// 返回当前连接数
public int getnumActive() {
return numActive;
}
}
