使用预处理的JDBC

public static void login() throws ClassNotFoundException, SQLException{
		//注册驱动
		Class.forName("org.gjt.mm.mysql.Driver");
		//获取连接
		Connection conn=DriverManager.getConnection("jdbc:mysql://localhost:3306/teachmanage","dev","dev");
		//编写sql
		String sql="select *from class_main where cid=?";
		//创建预处理对象
		PreparedStatement pstmt=conn.prepareStatement(sql);
		//设置参数（占位符）
		pstmt.setInt(1,2);
		//执行查询操作
		ResultSet rs=pstmt.executeQuery();		
		//结果集
		int i=1;
		if(rs.next()){			
			while(i<6){
			System.out.print(rs.getString(i++));
			}					
			System.out.println("输完");
			
		}
		if(rs!=null)rs.close();
		if(pstmt!=null)pstmt.close();
		if(conn!=null)conn.close();
	}