一个简单的MySql数据库连接池的实现

package cn.hc.connectionPool;

import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.LinkedList;
import java.util.Properties;


/**
 * 简单的MySql数据库连接池
 * @author hc
 * @version 1.0
 */
public class ConnectionPool {
    private LinkedList<Connection> connections=new LinkedList<Connection>();
    //默认的数据库连接池大小为5
    private static int initSize=5;
    private static int maxSize=5;
    private  int acturalSize=0;//数据库连接池的实际大小
    private static Properties props = null;
    static{
        try {
            InputStream in = ConnectionPool.class.getClassLoader()
                    .getResourceAsStream("dbconfig.properties");
            props = new Properties();
            props.load(in);
        } catch(IOException e) {
            throw new RuntimeException(e);
        }
        
        try {
            String size=props.getProperty("initSize");
            String size2=props.getProperty("maxSize");
            if(size!=null){
                initSize=Integer.parseInt(size);
            }
            if(size2!=null){
                maxSize=Integer.parseInt(size2);
            }
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
    //获取连接的静态内部类
    static class GetCon{
        static{
            try {
                Class.forName(props.getProperty("driverClassName"));
            } catch (ClassNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        static Connection getConnection() throws SQLException{
            return  DriverManager.getConnection(props.getProperty("url"),
                    props.getProperty("username"), 
                    props.getProperty("password"));
        }
    }
    public ConnectionPool(){
        //初始化数据库连接池
        for (int i = 0; i<initSize; i++) {
            try {
                connections.addLast(GetCon.getConnection());
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            acturalSize++;
            
        }
    }
    /**
     * 该方法用来释放连接，将connection对象放回到数据库连接池,实现对数据库连接池大大小的增减
     * @param connection 要放回数据库连接池的连接
     */
    public void releseConnection(Connection connection){
        if(connection!=null){
            synchronized (connections) {
                if(connections.size()>initSize){
                    try {
                        connection.close();
                        acturalSize--;
                    } catch (SQLException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                    
                }else{
                    connections.addLast(connection);
                }
                
                connections.notifyAll();//唤醒所有等待获取连接的对象
            }
        }
    }
    /**
     * 该方法用来从数据库连接池获取连接
     * @param mills 获取连接的超时时间 单位毫秒,当设置的值为0时候，即不要求等待时间
     * @return connection对象
     * @throws SQLException 
     * @throws InterruptedException 
     */
    public Connection getConnection(long mills) throws SQLException, InterruptedException{
        synchronized (connections) {
            if(mills<=0){
                while (connections.isEmpty()) {
                    if(acturalSize<maxSize){
                        Connection con= DriverManager.getConnection(props.getProperty("url"),
                                props.getProperty("username"), 
                                props.getProperty("password"));
                        acturalSize++;
                        return con;
                    }else{
                        connections.wait();
                    }
                }
                return connections.removeFirst();
            }else{
                if(acturalSize<maxSize){
                    Connection con= DriverManager.getConnection(props.getProperty("url"),
                            props.getProperty("username"), 
                            props.getProperty("password"));
                    acturalSize++;
                    return con;
                }else{
                    long future=System.currentTimeMillis()+mills;
                    long remaining=mills;
                    while(connections.isEmpty()&&remaining>0){
                        connections.wait(remaining);
                        remaining=future-System.currentTimeMillis();
                    }
                    Connection result=null;
                    if(!connections.isEmpty()){
                        result=connections.removeFirst();
                    }
                    return result;
                }
            }
        }
    }
}

配置文件：

driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/acled?rewriteBatchedStatements=true
username=root
password=123
initSize=5
maxSize=7