源代码：
/*
*
@Title
连接池
*
@Author: zxg
*
@Version 1.0
*
@Memo:定义数据库连接及其数据库连接池等
*/
package com.drsl.db;
import java.io.*;
import java.sql.*;
import java.util.*;
import java.util.Date;
import java.lang.reflect.*;
import com.mysql.jdbc.Driver;
import com.drsl.db.*;
public class ConnectionManager {
static private ConnectionManager instance; // 唯一实例
static private int clients;
static private int maxonlinetime=30*60*1000;
private Vector drivers = new Vector();
private Hashtable pools = new Hashtable();
private Timer checkConnTimer=new Timer();
static private PrintWriter log;
/**
* 返回唯一实例.如果是第一次调用此方法,则创建实例
*
* @return ConnectionManager 唯一实例
*/
static synchronized public ConnectionManager getInstance() {
if (instance == null) {
instance = new ConnectionManager();
}
//
clients++;
return instance;
}
/**
* 建构函数私有以防止其它对象创建本类实例
*/
private ConnectionManager() {
init();
}
/**
* 读取属性完成初始化
*/
private void init() {
try {
InputStream
is =
getClass().getResourceAsStream("db.properties");
Properties
dbProps = new Properties();
dbProps.load(is);
}
catch (Exception e) {
e.printStackTrace();
System.err.println("不能读取属性文件= " +
"请确保db.properties在CLASSPATH指定的路径中");
return;
}
String logFile = dbProps.getProperty("logfile", "log.txt");
try {
log = new PrintWriter(new FileWriter(logFile, true), true);
}
catch (IOException e) {
System.err.println("无法打开日志文件: " + logFile);
log = new PrintWriter(System.err);
}
loadDrivers(dbProps);
createPools(dbProps);
}
/**
* 装载和注册所有JDBC驱动程序
*
* @param props 属性
*/
private void loadDrivers(Properties props) {
String driverClasses = props.getProperty("drivers");
StringTokenizer st = new StringTokenizer(driverClasses);
while (st.hasMoreElements()) {
String driverClassName = st.nextToken().trim();
try {
Driver driver = (Driver)Class.forName(driverClassName).newInstance();
if(driver!=null){
DriverManager.registerDriver(driver);
drivers.addElement(driver);
log("Begin");
log("成功注册JDBC驱动程序" + driverClassName);
}
else{
log("Begin");
log("注册JDBC驱动程序" + driverClassName+"失败");
}
}
catch (Exception e) {
log("Begin");
log("无法注册JDBC驱动程序: " + driverClassName + ", 错误: " + e);
}
}
}
/**
* 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) {
Enumeration propNames = props.propertyNames();
while (propNames.hasMoreElements()) {
String name = (String) propNames.nextElement();
if (name.endsWith(".url")) {
String poolName = name.substring(0, name.lastIndexOf("."));
String url = props.getProperty(poolName + ".url");
if (url == null) {
log("没有为连接池" + poolName + "指定URL");
continue;
}
String user = props.getProperty(poolName + ".user");
String password = props.getProperty(poolName + ".password");
String maxconn = props.getProperty(poolName + ".maxconn", "0");
String minconn = props.getProperty(poolName + ".minconn", "10");
String option=props.getProperty(poolName+".option","");
int max,min;
try {
max = Integer.valueOf(maxconn).intValue();
}
catch (NumberFormatException e) {
log("错误的最大连接数限制: " + maxconn + " .连接池: " + poolName);
max = 0;
}
try {
min = Integer.valueOf(minconn).intValue();
}
catch (NumberFormatException e) {
log("错误的最小连接数限制: " + minconn + " .连接池: " + poolName);
min = 0;
}
try{
ConnectionPool pool = new ConnectionPool(poolName, url,user,password,min,max,option);
pools.put(poolName, pool);
//2秒钟后开始每个一分钟检查一次连接池情况
checkConnTimer.schedule(pool,2000,60*1000);
log("成功创建连接池" + poolName);
}catch(Exception e){
log(e,"创建DBConnectionPool出错");
}
}
}
}
/**
* 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 连接对象
*/
public void freeConnection(String name, Connection conn) {
ConnectionPool pool = (ConnectionPool) pools.get(name);
if (pool != null) {
pool.freeConnection(conn);
}
}
/**
* 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
*
* @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) {
ConnectionPool pool = (ConnectionPool) pools.get(name);
if (pool != null) {
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.
*
* @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
*/
public Connection getConnection(String name, long time) {
ConnectionPool pool = (Con