JDBC 创建连接对象的三种方式

　　　　 //第一种方式
        Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb?user=root&password=root") ;
        


　　　　 //第二种方式
        //读取properties文件
        Properties pro = new Properties() ;
        InputStream in = JdbcDemo3.class.getClassLoader().getResourceAsStream("dbcfg.properties") ;
        pro.load(in) ;
        Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb", pro) ;



        //第三种方式
        Connection conn = DriverManager.getConnection(url,user,password) ; 

    private static String driverClass = "" ;
    private static String url = "" ;
    private static String user = "" ;
    private static String password  = "";
    
    static{
        ResourceBundle rb = ResourceBundle.getBundle("dbcfg") ;
        driverClass = rb.getString("driverClass") ;
        url = rb.getString("url") ;
        user = rb.getString("user") ;
        password = rb.getString("password") ;
        
        try {
            Class.forName(driverClass) ;//自动注册驱动
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    
    public static Connection getConnection(){
        try {
            return DriverManager.getConnection(url, user, password) ;
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return null ;
    }