[JDBC]PreparedStatement替代Statement

一.增

复制代码

    @Test
    public void testInsert() throws Exception {
        try(Connection con = ConnectDB();
            Scanner input = new Scanner(System.in)){

            System.out.print("请输入姓名：");
            String ename = input.next();//李四

            System.out.print("请输入薪资：");
            double salary = input.nextDouble();//15000

            System.out.print("请输入出生日期：");
            String birthday = input.next();//1990-1-1

            System.out.print("请输入性别：");
            char gender = input.next().charAt(0);//男
//        String gender = input.next();

            System.out.print("请输入手机号码：");
            String tel = input.next();//13578595685

            System.out.print("请输入邮箱：");
            String email = input.next();//zhangsan@atguigu.com

            //编写sql
            String sql = "insert into t_employee(ename,salary,birthday,gender,tel,email,hiredate) " +
                    "values(?,?,?,?,?,?,curdate())";

            //告诉数据库执行 INSERT 操作后，返回自动生成的主键值（比如自增 ID）
            PreparedStatement preparedStatement = con.prepareStatement(sql, Statement.RETURN_GENERATED_KEYS);
            //需要填写？对应的值
            preparedStatement.setObject(1, ename);
            preparedStatement.setObject(2, salary);
            preparedStatement.setObject(3, birthday);
            preparedStatement.setObject(4, gender + "");//char变为String类型
            preparedStatement.setObject(5, tel);
            preparedStatement.setObject(6, email);

            int len = preparedStatement.executeUpdate();
            if(len > 0){
                System.out.println("添加成功！ len = " +  len);
            }else{
                System.out.println("添加失败！");
            }
            preparedStatement.close();
        }
    }

一个关于PeparedStatement的insert的错误

二.删

复制代码

@Test
public void testDelete() throws Exception {
    String sql = "delete from t_employee where eid = ?";
    try(Connection con = ConnectDB();
        PreparedStatement ps = con.prepareStatement(sql, Statement.RETURN_GENERATED_KEYS);){
        ps.setInt(1,32);
        int len = ps.executeUpdate();
        if(len > 0){
            System.out.println("删除成功！ len = " + len);
        }else{
            System.out.println("删除失败！");
        }
    }
    catch (Exception e){
        e.printStackTrace();
    }
}

三.改

复制代码

@Test
public void testUpdate() throws Exception {
    try(Connection con = ConnectDB();
    PreparedStatement ps = con.prepareStatement("update t_employee set ename = ? where eid = ?");
    Scanner input = new Scanner(System.in)){

        System.out.println("请输入要修改的姓名：");
        String ename = input.next();
        System.out.println("请输入要修改的员工ID：");
        int eid = input.nextInt();
        ps.setString(1,ename);
        ps.setInt(2, eid);

        int len = ps.executeUpdate();
        if(len > 0){
            System.out.println("修改成功！ len = " + len);
        }else{
            System.out.println("修改失败！");
        }

    }catch(Exception e){
        e.printStackTrace();
    }
}