注册Jdbc驱动程序的三种方式
1、比较常用
try{
       Class.forName("com.mysql.jdbc.Driver");//加载数据库驱动
       String url="jdbc:mysql://localhost:3306/databasename";//数据库连接子协议
       Connection conn=DriverManager.getConnection(url,"username","password");
       Statement stmt=conn.createStatement();
       ResultSet rs=stmt.executeQuery("select * from tablename");
       while(rs.next()){//不断指向下一条记录
            System.out.println("DeptNo:"+rs.getInt(1));
            System.out.println("\tDeptName:"+rs.getString(2));
            System.out.println("\tLOC:"+rs.getString(3));
}        
    rs.close();
    stmt.close();
    conn.close();
}catch(ClassNotFoundException e){
   System.out.println("找不到指定的驱动程序类！");
}catch(SQLException e){
    e.printStackTrace();
}


2、通过系统的属性设置
try{
       System.setProperty("jdbc.driver","com.mysql.jdbc.Driver");//系统属性指定数据库驱动
       String url="jdbc:mysql://localhost:3306/databasename";//数据库连接子协议
       Connection conn=DriverManager.getConnection(url,"username","password");
       Statement stmt=conn.createStatement();
       ResultSet rs=stmt.executeQuery("select * from tablename");
       while(rs.next()){//不断指向下一条记录
            System.out.println("DeptNo:"+rs.getInt(1));
            System.out.println("\tDeptName:"+rs.getString(2));
            System.out.println("\tLOC:"+rs.getString(3));
}        
    rs.close();
    stmt.close();
    conn.close();
}catch(SQLException e){
    e.printStackTrace();
}

3、看起来比较直观的一种方式，注册相应的db的jdbc驱动，3在编译时需要导入对应的lib
try{
       new com.mysql.jdbc.Driver();//创建driver对象，加载数据库驱动
       String url="jdbc:mysql://localhost:3306/databasename";//数据库连接子协议
       Connection conn=DriverManager.getConnection(url,"username","password");
       Statement stmt=conn.createStatement();
       ResultSet rs=stmt.executeQuery("select * from tablename");
       while(rs.next()){//不断指向下一条记录
            System.out.println("DeptNo:"+rs.getInt(1));
            System.out.println("\tDeptName:"+rs.getString(2));
            System.out.println("\tLOC:"+rs.getString(3));
}        
    rs.close();
    stmt.close();
    conn.close();
}catch(SQLException e){
    e.printStackTrace();
}