package com.gd.jdbc;

import java.sql.Connection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

import com.gd.jdbc.impl.GdDbConnectionPool;

public class DbConnectionManager {
	
	static private DbConnectionManager instance; //單例模式 
	private static Map connPool = new HashMap();
	/** 
	* 返回唯一實例.如果是第一次調用此方法,則創建實例 
	* @return DbConnectionManager 
	*/ 
	static synchronized public DbConnectionManager getInstance() { 
		if (instance == null) { 
		instance = new DbConnectionManager(); 
		} 
		return instance; 
	} 

	/** 
	* 防止其它對象創建本類的實例 
	*/ 
	private DbConnectionManager() { 
		init(); 
	} 
	/**
	 * 根據名稱從map中獲取連接
	 * @param name
	 * @return
	 */
	public static Connection getConnection(String name) { 
		Connection conn = null;
		try {
			//從連接池中獲取連接
			DbConnectionPool pool = (GdDbConnectionPool)connPool.get(name);
			if (pool != null)
				conn = pool.getConnection();
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			return conn;
		}		
	} 
	/** 
	* 將連接返回給連接池 
	* @param name 連接池名字 
	* @param con 連接對象 
	*/ 
	public static void returnConnection(String name, Connection conn) { 
		try {
			DbConnectionPool pool = (GdDbConnectionPool)connPool.get(name);
			if (pool != null)
				pool.returnConnection();
		} catch (Exception e) {
			e.printStackTrace();
		} 
	} 
	/** 
	* 關閉所有連接 
	*/ 
	public synchronized void release() { 
		try {
			Set set = connPool.entrySet();
			Iterator iterator = set.iterator();
			while (iterator.hasNext()) {
				Map.Entry map = (Map.Entry)iterator.next();
				DbConnectionPool pool = (GdDbConnectionPool)map.getValue();
				//關閉連接池
				pool.setConnWitch("OFF");
			}
			connPool = null;
		} catch (Exception e) {
			e.printStackTrace();
		}	
	} 
	/** 
	* 創建連接池
	* @param props 連接池屬性 
	*/ 
	private void createPools() { 
		DbConnectionPool pool = new GdDbConnectionPool();
		//設定連接池的大小
		pool.setMaxConns(10);
		try {
			//表示創建連接池
			pool.setConnWitch("ON");
			//將創建后的連接池放在Map中,用mysql表示是用于連接mysql數據庫的
			connPool.put("mysql", pool);
		} catch (Exception e) {
			e.printStackTrace();
		}		
	} 
	/** 
	* 初始化 
	*/ 
	private void init() { 
		//創建連接池
		createPools();
	}
}