[Java知识库]Mybatis--注解开发--CURD

前言

??????? Mybatis使用注解只能实行一些简单的SQL

??????? 它只需要在编写接口时,在接口上加上个注解,就不用在mapper.xml配置文件中编写了

??????? user类结构

public class User {
    private int id;
    private String name;
    private String pwd;
}

查询

接口

查询user表中所有的记录

@Select("select * from user")
    List<User> getUsers();

通过查询对应姓名的用户信息

@Select("select * from user where name=#{name}")
User getUserByName(@Param("name") String name);

测试

//查询所有用户
    @Test
    public void getUsers(){
        //1.获取SqlSession对象
        SqlSession sqlSession = getSqlSession();

        //调用
        UserMapper userMapper =sqlSession.getMapper(UserMapper.class);
        List<User> userList =userMapper.getUsers();

        for (User user : userList) {
            System.out.println(user);
        }
        //关闭
        sqlSession.close();
    }

    //通过姓名查询用户信息
    @Test
    public void getUserByName(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        UserMapper mapper =sqlSession.getMapper(UserMapper.class);
        User user=mapper.getUserByName("周星星");

        System.out.println(user);
        sqlSession.close();
    }

插入

接口

往user表插入一条新的记录

@Insert("insert into user(id,name,pwd) values(#{id},#{name},#{pwd})")
    int addUser(User user);

测试

@Test
    public void addUser(){
        //1.获取SqlSession对象
        SqlSession sqlSession = getSqlSession();

        //调用
        UserMapper userMapper =sqlSession.getMapper(UserMapper.class);
        userMapper.addUser(new User(369,"尚下九","147"));

        //提交事务
        sqlSession.commit();
        //关闭
        sqlSession.close();
    }

修改

接口

更新用户信息

@Update("update user set name=#{name},pwd=#{pwd} where id=#{id}")
    int updateUser(User user);

测试

    @Test
    public void updateUser(){
        //1.获取SqlSession对象
        SqlSession sqlSession = getSqlSession();

        //调用
        UserMapper userMapper =sqlSession.getMapper(UserMapper.class);
        userMapper.updateUser(new User(369,"三六九","258"));

        //提交事务
        sqlSession.commit();
        //关闭
        sqlSession.close();
    }

删除

接口

删除一个用户

@Delete("delete from user where id=#{id}")
    int deleteById(@Param("id") Integer id);

测试

    @Test
    public void deleteById(){
        //1.获取SqlSession对象
        SqlSession sqlSession = getSqlSession();

        //调用
        UserMapper userMapper =sqlSession.getMapper(UserMapper.class);
        userMapper.deleteById(369);

        //提交事务
        sqlSession.commit();
        //关闭
        sqlSession.close();
    }

@Param注解

基本类型的参数或者String类型，需要加上
引用类型不需要加
如果只有一个基本类型的话，可以忽略，但是建议大家都加上!
我们在SQL中引用的就是我们这里的@Param()中设定的属性名!