package com.xuanke.utils;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

/**
 * 
 * @author wengwy
 *  數(shù)據(jù)庫連接池類，
 *  使用方法：
 *  1、通過調(diào)用靜態(tài)函數(shù)setParameter設(shè)置數(shù)據(jù)庫連接的參數(shù)
 *  	同時(shí)加載數(shù)據(jù)庫驅(qū)動(dòng)程序，如果加載失敗，則拋出MyJDBCException
 *  2、通過調(diào)用靜態(tài)函數(shù)getConnection獲取數(shù)據(jù)庫連接，
 *      如果連接失敗，則拋出MyJDBCException
 *      如果1秒鐘連接不上,則返回空
 *  3、通過freeConnection釋放連接
 *      
 */
public class DBConnectionManager {
	private static String jdbcDriver,jdbcUrl,dbuser,dbpassword;
	public static void setParameter(String driver,String url,String user,String pwd) throws MyJDBCException{
		jdbcDriver=driver;
		jdbcUrl=url;
		dbuser=user;
		dbpassword=pwd;
		try {
			Class.forName(driver);
		} catch (ClassNotFoundException e) {
			throw new MyJDBCException("加載數(shù)據(jù)庫驅(qū)動(dòng)程序失敗");
		}
	}
	private static final int poolsize=10;//連接池最多數(shù)據(jù)庫連接數(shù)
	private static Connection[] conns=new Connection[poolsize];
	private static boolean[] inused=new boolean[poolsize];
	
	public static Connection getConnection()throws MyJDBCException{
		for(int k=0;k<5;k++){
			for(int i=0;i<poolsize;i++){
				if(!inused[i]){//第i個(gè)連接空閑
					if(conns[i]==null){//第一次使用該連接時(shí)建立數(shù)據(jù)庫連接
						try {
							conns[i]=DriverManager.getConnection(jdbcUrl,dbuser,dbpassword);
						} catch (SQLException e) {
							throw new MyJDBCException("無法連接數(shù)據(jù)庫");
						}
					}
					inused[i]=true;
					return conns[i];
				}
			}
			try {
				Thread.sleep(200);  //如沒有空閑，等待200毫秒后繼續(xù)
			} catch (InterruptedException e) {
				// TODO 自動(dòng)生成 catch 塊
				
			}
		}
		return null;
	}
	public static void freeConnection(Connection conn){
		for (int i=0;i<poolsize;i++){
			if(conns[i]==conn){
				inused[i]=false;
				return;
			}
		}
	}

}