我给你一个我们项目用的连接池:
/**
* 数据库连接池管理类
*/
import java.io.*;
import java.sql.*;
import java.util.*;
import java.util.Date;/**
* 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 { static private DBConnectionManager instance; // 唯一实例
static private int clients; //
private Vector drivers = new Vector();
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
*/
static synchronized public DBConnectionManager getInstance() {
if (instance == null) {
instance = new DBConnectionManager();
}
clients++;
return instance;
} /**
* 建构私有函数以防止其它对象创建本类实例
*/
private DBConnectionManager() {
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 连接对象
*/
public void freeConnection(String name, Connection con) {
DBConnectionPool pool = (DBConnectionPool) pools.get(name);
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
*
* @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) {
DBConnectionPool pool = (DBConnectionPool) 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) {
DBConnectionPool pool = (DBConnectionPool) pools.get(name);
if (pool != null) {
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() {
// 等待直到最后一个客户程序调用
if (--clients != 0) {
return;
} Enumeration allPools = pools.elements();
while (allPools.hasMoreElements()) {
DBConnectionPool pool = (DBConnectionPool) allPools.nextElement();
pool.release();
} Enumeration allDrivers = drivers.elements();
while (allDrivers.hasMoreElements()) {
Driver driver = (Driver) allDrivers.nextElement();
try {
DriverManager.deregisterDriver(driver);
log("撤销JDBC驱动程序 " + driver.getClass().getName()+"的注册");
}
catch (SQLException e) {
log(e, "无法撤销下列JDBC驱动程序的注册: "
+ driver.getClass().getName());
}
}
} /**
* 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");
int max;
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;
}
DBConnectionPool pool =
new DBConnectionPool(poolName, url, user, password, max);
pools.put(poolName, pool);
log("成功创建连接池" + poolName);
}
}
}
/**
* 数据库连接池管理类
*/
import java.io.*;
import java.sql.*;
import java.util.*;
import java.util.Date;/**
* 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 { static private DBConnectionManager instance; // 唯一实例
static private int clients; //
private Vector drivers = new Vector();
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
*/
static synchronized public DBConnectionManager getInstance() {
if (instance == null) {
instance = new DBConnectionManager();
}
clients++;
return instance;
} /**
* 建构私有函数以防止其它对象创建本类实例
*/
private DBConnectionManager() {
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 连接对象
*/
public void freeConnection(String name, Connection con) {
DBConnectionPool pool = (DBConnectionPool) pools.get(name);
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
*
* @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) {
DBConnectionPool pool = (DBConnectionPool) 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) {
DBConnectionPool pool = (DBConnectionPool) pools.get(name);
if (pool != null) {
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() {
// 等待直到最后一个客户程序调用
if (--clients != 0) {
return;
} Enumeration allPools = pools.elements();
while (allPools.hasMoreElements()) {
DBConnectionPool pool = (DBConnectionPool) allPools.nextElement();
pool.release();
} Enumeration allDrivers = drivers.elements();
while (allDrivers.hasMoreElements()) {
Driver driver = (Driver) allDrivers.nextElement();
try {
DriverManager.deregisterDriver(driver);
log("撤销JDBC驱动程序 " + driver.getClass().getName()+"的注册");
}
catch (SQLException e) {
log(e, "无法撤销下列JDBC驱动程序的注册: "
+ driver.getClass().getName());
}
}
} /**
* 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");
int max;
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;
}
DBConnectionPool pool =
new DBConnectionPool(poolName, url, user, password, max);
pools.put(poolName, pool);
log("成功创建连接池" + poolName);
}
}
}
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/**
* 读取属性完成初始化
*/
private void init() {
InputStream is = getClass().getResourceAsStream("db.properties"); Properties dbProps = new Properties();
try {
dbProps.load(is);
}
catch (Exception e) {
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", "DBConnectionManager.log");
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();
DriverManager.registerDriver(driver);
drivers.addElement(driver);
log("成功注册JDBC驱动程序" + driverClassName);
}
catch (Exception e) {
log("无法注册JDBC驱动程序: " +
driverClassName + ", 错误: " + e);
}
}
} /**
* 将文本信息写入日志文件
*/
private void log(String msg) {
log.println(new Date() + ": " + msg);
} /**
* 将文本信息与异常写入日志文件
*/
private void log(Throwable e, String msg) {
log.println(new Date() + ": " + msg);
e.printStackTrace(log);
}
/****************************************************************/
/**********************内部类DBConnectionPool*********************/
/****************************************************************/
/**
* 此内部类定义了一个连接池.它能够根据要求创建新连接,直到预定的最
* 大连接数为止.在返回连接给客户程序之前,它能够验证连接的有效性.
*/
class DBConnectionPool { private int checkedOut; //当前连接数
private Vector freeConnections = new Vector(); //保存所有可用连接
private int maxConn; //此连接池允许建立的最大连接数
private String name; //连接池名字
private String password; //密码或null
private String URL; //数据库的JDBC URL
private String user; //数据库账号或null /**
* 创建新的连接池
*
* @param name 连接池名字
* @param URL 数据库的JDBC URL
* @param user 数据库帐号或 null
* @param password 密码或 null
* @param maxConn 此连接池允许建立的最大连接数
*/
public DBConnectionPool(String name, String URL, String user, String
password , int maxConn) { this.name = name;
this.URL = URL;
this.user = user;
this.password = password;
this.maxConn = maxConn;
} /**
* 将不再使用的连接返回给连接池
*
* @param con 客户程序释放的连接
*/
public synchronized void freeConnection(Connection con) {
//将指定连接加入到向量末尾
freeConnections.addElement(con);
checkedOut--;
notifyAll(); //删除等待队列中的所有线程
} /**
* 从连接池获得一个可用连接.如果没有空闲的连接且当前连接数小于最大连接
* 数限制,则创建新连接.如原来登记为可用的连接不再有效,则从向量删除之,
* 然后递归调用自己以尝试新的可用连接.
*/
public synchronized Connection getConnection() {
Connection con = null;
if (freeConnections.size() > 0) {
// 获取向量中第一个可用连接
con = (Connection) freeConnections.firstElement();
freeConnections.removeElementAt(0);
try {
if (con.isClosed()) {
log("从连接池" + name + "删除一个无效连接"); // 递归调用自己,尝试再次获取可用连接
con = getConnection();
}
}
catch (SQLException e) {
log("从连接池" + name + "删除一个无效连接");
// 递归调用自己,尝试再次获取可用连接
con = getConnection();
}
}
else if (maxConn == 0 || checkedOut < maxConn) {
con = newConnection();
}
if (con != null) {
checkedOut++;
}
return con;
} /**
* 从连接池获取可用连接.可以指定客户程序能够等待的最长时间
* 参见前一个getConnection()方法.
* @param timeout 以毫秒计的等待时间限制
*/
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) {
// wait()返回的原因是超时
return null;
}
}
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();
log("关闭连接池" + name + "中的一个连接");
}
catch (SQLException e) {
log(e, "无法关闭连接池" + name + "中的连接");
}
}
freeConnections.removeAllElements();
} /**
* 创建新的连接
*/
private Connection newConnection() {
Connection con = null;
try {
if (user == null) {
con = DriverManager.getConnection(URL);
}
else {
con = DriverManager.getConnection(URL, user, password);
}
log("连接池" + name + "创建一个新的连接");
}
catch (SQLException e) {
log(e, "无法创建下列URL的连接: " + URL);
return null;
}
return con;
}
}
}
配置文件如下:
drivers=oracle.jdbc.driver.OracleDriver
logfile=d:\\log.txt
idb.maxconn=4idb.url=**
idb.user=***
idb.password=***
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去看看吧,关于连接池的网上到处都是
import java.sql.*; public class ConnectionPool implements Runnable
{
// Number of initial connections to make.
private int m_InitialConnectionCount = 5;
// A list of available connections for use.
private Vector m_AvailableConnections = new Vector();
// A list of connections being used currently.
private Vector m_UsedConnections = new Vector();
// The URL string used to connect to the database
private String m_URLString = null;
// The username used to connect to the database
private String m_UserName = null;
// The password used to connect to the database
private String m_Password = null;
// The cleanup thread
private Thread m_CleanupThread = null;
//Constructor
public ConnectionPool(String urlString, String user, String passwd) throws SQLException
{
// Initialize the required parameters
m_URLString = urlString;
m_UserName = user;
m_Password = passwd; for(int cnt=0; cnt<m_InitialConnectionCount; cnt++)
{
// Add a new connection to the available list.
m_AvailableConnections.addElement(getConnection());
}
// Create the cleanup thread
m_CleanupThread = new Thread(this);
m_CleanupThread.start();
}
private Connection getConnection() throws SQLException
{
return DriverManager.getConnection(m_URLString, m_UserName, m_Password);
}
public synchronized Connection checkout() throws SQLException
{
Connection newConnxn = null;
if(m_AvailableConnections.size() == 0)
{
// Im out of connections. Create one more.
newConnxn = getConnection();
// Add this connection to the "Used" list.
m_UsedConnections.addElement(newConnxn);
// We dont have to do anything else since this is
// a new connection.
}
else
{
// Connections exist !
// Get a connection object
newConnxn = (Connection)m_AvailableConnections.lastElement();
// Remove it from the available list.
m_AvailableConnections.removeElement(newConnxn);
// Add it to the used list.
m_UsedConnections.addElement(newConnxn);
}
// Either way, we should have a connection object now.
return newConnxn;
}
public synchronized void checkin(Connection c)
{
if(c != null)
{
// Remove from used list.
m_UsedConnections.removeElement(c);
// Add to the available list
m_AvailableConnections.addElement(c);
}
}
public int availableCount()
{
return m_AvailableConnections.size();
}
public void run()
{
try
{
while(true)
{
synchronized(this)
{
while(m_AvailableConnections.size() > m_InitialConnectionCount)
{
// Clean up extra available connections.
Connection c = (Connection)m_AvailableConnections.lastElement();
m_AvailableConnections.removeElement(c);
// Close the connection to the database.
c.close();
}
// Clean up is done
}
System.out.println("CLEANUP : Available Connections : " + availableCount());
// Now sleep for 1 minute
Thread.sleep(60000 * 1);
}
}
catch(SQLException sqle)
{
sqle.printStackTrace();
}
catch(Exception e)
{
e.printStackTrace();
}
}
}
连接池的主要思想:
1。Requests for Connection
2.Unused connection moves to used list.
3.Connection Pool returns unused connection
4.After using connection,modules return them,the connection pool returns them to the unused pool.