其实就是将数据库连接的Connection对象放在自定义的数据结构中，在需要数据库连接的时候，从该结构中取得即可。

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package com.woo.demo.jdbc.util;

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

public class MyDataSource {
	private String url="jdbc:hsqldb:hsql://localhost/woo";
	private String user="sa";
	private String pwd="";
	
	private static LinkedList<Connection> connectionPool=new LinkedList<Connection>();
	private final int connectionNum=5;
	private final int maxConnection=10;
	private int currentConnectionNum=0;
	
	public MyDataSource() {
		try {
			for (int i = 0; i < connectionNum; i++) {
				connectionPool.addLast(this.createConnection());
			}
		} catch (Exception e) {
			throw new ExceptionInInitializerError(e);
		}
	}
	
	/**
	 * 获取连接
	 * @return
	 * @throws SQLException
	 */
	public Connection getConnection()throws SQLException{
		synchronized (connectionPool) {
			if(connectionPool.size()>0){
				currentConnectionNum++;
				return connectionPool.removeFirst();
			}
			if(currentConnectionNum<maxConnection){
				currentConnectionNum++;
				return this.createConnection();
			}
			throw new SQLException("超过最大连接数");
		}
	}
	
	/**
	 * 释放连接
	 * @param con
	 */
	public void freeConnection(Connection con){
		currentConnectionNum--;
		connectionPool.addLast(con);
	}
	
	/**
	 * 创建连接
	 * @return
	 */
	private Connection createConnection(){
		Connection con=null;
		try{
			con=DriverManager.getConnection(url, user, pwd);
		}
		catch (Exception e) {
			throw new ExceptionInInitializerError(e);
		}
		return con;
	}
}