package com.wangjia.tools;

        import java.io.Serializable;
        import java.sql.*;
        import java.util.*;

        /**
        * 数据库连接池的简单实现
        * @author wangjia
        * @version 1.0
        *@serial 2301410997974776106L
        */
        public class DbConn implements Serializable{

        /**
        * 
        */
        private static final long serialVersionUID = 2301410997974776106L;
        private static List<Connection> connList=new ArrayList<Connection>();
        //private static String driver="com.microsoft.jdbc.sqlserver.SQLServerDriver";//sql2000
        private static String driver="com.microsoft.sqlserver.jdbc.SQLServerDriver";//sql2005
        private static String url="jdbc:sqlserver://127.0.0.1:1433;DatabaseName=Forum";
        private static String userName="sa";
        private static String password="sa";
        private static int maxConn=20;
        private static int minConn=5;
        private static int usedConn=0;
        private static DbConn dbconn=null;
        // private static int flag=1;
        /**
        * 设置数据库连接的驱动
        * @param driver 数据库连接的驱动<br/>例如:"com.microsoft.sqlserver.jdbc.SQLServerDriver"
        */
        public static void setDriver(String driver) {
        DbConn.driver = driver;
        }

        /**
        * 设置数据库连接池的最小数量
        * @param maxConn 数据库连接池的最小数量
        */
        public static void setMaxConn(int maxConn) {
        DbConn.maxConn = maxConn;
        }

        /**
        * 设置数据库连接池的最大数量
        * @param minConn 数据库连接池的最大数量
        */
        public static void setMinConn(int minConn) {
        DbConn.minConn = minConn;
        }

        /**
        * 设置数据库连接的URL
        * @param url 数据库连接的URL,包括数据库的名称<br/>例如: "jdbc:sqlserver://127.0.0.1:1433;DatabaseName=master"
        */
        public static void setUrl(String url) {
        DbConn.url = url;
        }

        private DbConn() throws MyException{
        try{
        Class.forName(driver);
        for(int i=0;i<minConn;i++){
        connList.add(DriverManager.getConnection(url,userName.toString(),password.toString()));
        }
        }catch(ClassNotFoundException e){
        throw new MyException("请设置正确的数据库连接驱动!\nusing: DbConn.setDriver(String driver)");

        }catch(SQLException e){
        throw new MyException("请设置正确的数据库连接URL以及用于连接的用户名和密码!\n" +
        "using: DbConn.setUrl(String url),DbConn.setUserName(String userName),DbConn.setPassword(String password)");

        }
        }
        /**
        * 用于得到DbConn对象
        * @return 返回一个DbConn对像
        */


        public static Connection getConn() throws MyException{
        // flag++;
        if(dbconn==null)dbconn=new DbConn();
        // System.out.println("falg="+flag);
        // System.out.println("usedConn="+usedConn);
        if(connList.size()==0){
        throw new MyException("没有正确的设置相关信息,以至连接池未初始化");
        }
        if(usedConn==maxConn){

        Thread thread=new Thread(new Runnable(){

        @SuppressWarnings("static-access")
        public void run() {
        if(usedConn<maxConn){
        try {
        try {
        Thread.currentThread().sleep(2000);
        } catch (InterruptedException e) {
        e.printStackTrace();
        }
        getConn();
        } catch (MyException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
        }
        }

        }

        });
        thread.start();
        }
        if(usedConn>=minConn&&usedConn<maxConn){
        try {
        connList.add(DriverManager.getConnection(url,userName.toString(),password.toString()));
        } catch (SQLException e) {

        }
        return connList.get(usedConn++);
        }
        if(usedConn<5){
        return connList.get(usedConn++);
        }
        return null;
        }

        public static void close(){
        try {
        if(usedConn>5)
        connList.get(--usedConn).cl