一个简单的数据库连接池（连接个数，连接时间限制）

/* 数据库连接池 ***********模块说明************** getInstance()返回POOL唯一实例,第一次调用时将执行构造函数 构造函数Pool()调用驱动装载loadDrivers()函数;连接池创建createPool()函数 loadDrivers()装载驱动 createPool()建连接池 getConnection()返回一个连接实例 getConnection(long time)添加时间限制 freeConnection(Connection con)将con连接实例返回到连接池 getnum()返回空闲连接数 getnumActive()返回当前使用的连接数 */ import java.sql.*; public class Pool { static private Pool instance = null; //定义唯一实例 private int maxConnect = 100;//最大连接数 private int normalConnect = 10;//保持连接数 private String password = "";//密码 private String url = "jdbc:mysql://localhost:3306/DB";//连接URL private String user = "";//用户名 private String driverName = "";//驱动类 Driver driver = null;//驱动变量 DBConnectionPool pool = null;//连接池实例变量 /** * 返回唯一实例 * @return */ static synchronized public Pool getInstance() { if (instance == null) { instance = new Pool(); } return instance; } /** * 将构造函数私有,不允许外界访问 */ private Pool() { loadDrivers(driverName); createPool(); } /** * 装载和注册所有JDBC驱动程序 * @param dri */ private void loadDrivers(String dri) { String driverClassName = dri; try{ driver = (Driver) Class.forName(driverClassName).newInstance(); DriverManager.registerDriver(driver); System.out.println("成功注册JDBC驱动程序" + driverClassName); }catch (Exception e) { System.out.println("无法注册JDBC驱动程序:" + driverClassName + ",错误:" + e); } } /** * 创建连接池 */ private void createPool() { pool = new DBConnectionPool(password, url, user, normalConnect, maxConnect); if (pool != null) { System.out.println("创建连接池成功"); }else { System.out.println("创建连接池失败"); } } /** * 获得一个可用的连接,如果没有则创建一个连接,且小于最大连接限制 * @return */ public Connection getConnection() { if (pool != null) { return pool.getConnection(); } return null; } /** * 获得一个连接,有时间限制 * @param time * @return */ public Connection getConnection(long time) { if (pool != null) { return pool.getConnection(time); } return null; } /** * 将连接对象返回给连接池 * @param con */ public void freeConnection(Connection con) { if (pool != null) { pool.freeConnection(con); } } /** * 返回当前空闲连接数 * @return */ public int getnum(){ return pool.getnum(); } /** * 返回当前连接数 * @return */ public int getnumActive(){ return pool.getnumActive(); } /** * 关闭所有连接,撤销驱动注册 */ public synchronized void release() { pool.release(); try { DriverManager.deregisterDriver(driver);//撤销驱动 System.out.println("撤销JDBC驱动程序 " + driver.getClass().getName()); }catch (SQLException e) { System.out.println("无法撤销JDBC驱动程序的注册:" + driver.getClass().getName()); } } } //生成数据连接池 import java.sql.*; import java.util.*; import java.util.Date; public class DBConnectionPool { private int checkedOut; private Vector<Connection> freeConnections = new Vector<Connection>(); private int maxConn; private String password; private String url; private String user; private static int num=0;//空闲的连接数 private static int numActive=0;//当前的连接数 public DBConnectionPool(String password, String url, String user,int normalConn, int maxConn) { this.password = password; this.url = url; this.user = user; this.maxConn = maxConn; 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 * @return */ 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 * @param timeout * @return */ 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) { System.out.println("超时了！！"); return null; //超时返回 } } return con; } /** * 关闭所有连接 */ @SuppressWarnings("unchecked") 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 * @return */ 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 * @return */ public int getnum(){ return num; } /** * 返回当前连接数 * @return */ public int getnumActive(){ return numActive; } }