四种连接数据库的方法（DriverManager、DataSource子类、DBCP、c3p0）

一、环境

1、数据库驱动jar文件

2、DBCP方法

Commons-dbcp.jar：连接池的实现

Commons-pool.jar：连接池实现的依赖库

资源文件

3、c3p0方法：

c3p0-0.9.1.2.jar

配置文件：c3p0-config.xml

二、连接操作

1.DriverManager方法;

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.SQLException;

public class DBConnection {

private static String driverClass = "com.mysql.jdbc.Driver";

private static String url = "jdbc:mysql://localhost:3306/test";

private static String username = "root";

private static String password = "123456";

private static Connection conn = null;

static{

try {

//注册驱动

// 不要把conn = DriverManager.getConnection(url, username, password);

//放在这里。防止所有用户都用一个Connection

Class.forName(driverClass);

} catch (Exception e) {

throw new RuntimeException(e);

}

public static Connection getConnection() throws SQLException{

conn = DriverManager.getConnection(url, username, password);

return conn;

}

2.使用DataSource子类方法;

资源文件DBConnection.properties

driverClass = com.mysql.jdbc.Driver

url = jdbc:mysql://localhost:3306/test

username = root

password = 123456

模拟数据连接池 DataSourcePool.java

package cn.langzi.jdbc.DataSource;

import java.io.InputStream;

import java.io.PrintWriter;

import java.lang.reflect.InvocationHandler;

import java.lang.reflect.Method;

import java.lang.reflect.Proxy;

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.SQLException;

import java.util.LinkedList;

import java.util.Properties;

import javax.sql.DataSource;

public class DataSourcePool implements DataSource {

private static String url = null;

private static String username = null;

private static String password = null;

private static int size = 10;

private static LinkedList<Connection> list = new LinkedList<Connection>();

static{

try {

InputStream in = DataSourcePool.class.getClassLoader()

.getResourceAsStream(

"cn/langzi/jdbc/DataSource/DBConnection.properties");

Properties prop = new Properties();

prop.load(in);

Class.forName(prop.getProperty("driverClass"));

url = prop.getProperty("url");

username = prop.getProperty("username");

password = prop.getProperty("password");

} catch (Exception e) {

throw new ExceptionInInitializerError(e);

}

private static DataSourcePool pool = new DataSourcePool();

//创建对象就初始化size个数据库连接

private DataSourcePool(){

for(int i=0;i<size;i++){

try {

Connection conn = DriverManager.getConnection(url, username, password);

System.out.println(conn);

list.add(conn);

} catch (SQLException e) {

e.printStackTrace();

}

public static DataSourcePool getInstance(){

return pool;

}

@Override

public Connection getConnection() throws SQLException {

if(list.size()>0){

//取到连接，即从list中弹出一个Connection 连接

final Connection conn = list.pop();

//动态代理，返回一个代理对象

return (Connection) Proxy.newProxyInstance(DataSourcePool.class.getClassLoade(), conn.getClass().getInterfaces(), new InvocationHandler(){

public Object invoke(Object proxy, Method method, Object[] args)

throws Throwable {

//如果Connection调用的是close方法就将连接返回给数据连接池

if(method.getName().equals("close")){

list.push(conn);

return null;

}

return method.invoke(conn, args);

}

});

}

//连接用完

throw new RuntimeException("对不起，服务器繁忙！！！");

}

@Override

public Connection getConnection(String username, String password)

throws SQLException {