dbconnectionmanager.java

图书馆管理系统 能满足 查询

/*建立DBConnectionManager
 2002-10-15
 ver:1.0
 */
package com.jxyd.sql;

import java.io.*;
import java.sql.*;
import java.text.SimpleDateFormat;
import java.util.*;
import java.util.Date;

public class DBConnectionManager {

	static private DBConnectionManager instance;

	static private int clients;

	private Vector drivers = new Vector();

	// private PrintWriter log;
	private Hashtable pools = new Hashtable();

	// 返回唯一的实例
	static synchronized public DBConnectionManager getInstance() {
		if (instance == null) {
			instance = new DBConnectionManager();
		}
		clients++;
	//	System.out.println("客户端连接个数："+clients +"时间 "+new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date()));
		return instance;
	}

	// 构造函数
	private DBConnectionManager() {
		init();
	}

	// 释放一个连接
	public void freeConnection(String name, Connection con) {
		DBConnectionPool pool = (DBConnectionPool) pools.get(name);
		if (pool != null)
			pool.freeConnection(con);
	}

	// 取得一个连接
	public Connection getConnection(String name) {
		DBConnectionPool pool = (DBConnectionPool) pools.get(name);
		if (pool != null)
			return pool.getConnection();
		return 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
	public synchronized void release() {

		// 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);
				System.out.println("成功注销JDBC驱动程序:"
						+ driver.getClass().getName()+"22");
			} catch (SQLException e) {
				System.out.println("无法撤消JDBC驱动程序的注册"
						+ driver.getClass().getName());
			}
		}
		System.out.println("数据库连接池重新初始化完毕!");
		clients = 0;
		instance = null;
	}

	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("."));
				System.out.println(poolName);
				String url = props.getProperty(poolName + ".url");
				if (url == null) {
					System.out.println("没有连接池" + poolName + "指定的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) {
					System.out
							.println("错误的最大连接数" + maxconn + ".连接池" + poolName);
					max = 0;
				}
				DBConnectionPool pool = new DBConnectionPool(poolName, url,
						user, password, max);
				pools.put(poolName, pool);
				System.out.println("成功创建连接池" + poolName);
			}
		}
	}

	private void init() {
		InputStream is = getClass().getResourceAsStream("/db.properties");
		Properties dbProps = new Properties();
		try {
			dbProps.load(is);
		} catch (Exception e) {
			System.out.println("不能读取属性文件，请确保属性文件在classpath路径中");
			return;
		}
		loadDriver(dbProps);
		createPools(dbProps);
	}

	private void loadDriver(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);
				System.out.println("成功注册驱动程序" + driverClassName);
			} catch (Exception e) {
				System.out.println("无法注册驱动程序：" + driverClassName + "错误：" + e);
			}
		}
	}

	class DBConnectionPool {
		private int checkOut;

		private Vector freeConnections = new Vector();

		private int maxconn;

		private String name;

		private String password;

		private String URL;

		private String user;

		public DBConnectionPool(String name, String URL, String user,
				String password, int maxconn) {
			this.name = name;
			this.URL = URL;
			this.password = password;
			this.user = user;
			this.maxconn = maxconn;
		}

		public synchronized void freeConnection(Connection con) {
			freeConnections.addElement(con);
			checkOut--;
			notifyAll();
			// System.out.println(" 释放 1 条连接 最大连接数"+maxconn+"
			// 目前池中有"+freeConnections.size()+" 条可用连接" );

		}

		public synchronized Connection getConnection() {
			Connection con = null;
			if (freeConnections.size() > 0) {
				con = (Connection) freeConnections.firstElement();
				freeConnections.removeElementAt(0);
				try {
					if (con.isClosed()) {

						con = getConnection();
					}
				} catch (SQLException e) {

					con = getConnection();
				}
			} else if (maxconn == 0 || checkOut < maxconn) {
				con = newConnection();
			}
			if (con != null)
				checkOut++;
			return con;
		}

		public synchronized Connection getConnection(long timeOut) {
			long startTime = new java.util.Date().getTime();
			Connection con;
			while ((con = getConnection()) == null) {
				try {
					wait(timeOut);
				} catch (InterruptedException e) {
				}
				if ((new java.util.Date().getTime() - startTime) >= timeOut)
					return null;
			}
			return con;
		}

		public void release() {
			Enumeration allConnections = freeConnections.elements();
			while (allConnections.hasMoreElements()) {
				Connection con = (Connection) allConnections.nextElement();
				try {
					con.close();

				} catch (SQLException e) {
					System.out.println("无法关闭连接池" + name + "中的连接");
				}
			}
			freeConnections.removeAllElements();
		}

		private Connection newConnection() {
			Connection con = null;
			try {
				con = DriverManager.getConnection(URL, user, password);

			} catch (SQLException e) {
				System.out.println("无法创建一个URL的连接" + URL);
				return null;
			}
			return con;
		}

	}

}