MyBatis的常用注解
这几年来注解开发越来越流行，Mybatis也可以使用注解开发方式，这样我们就可以减少编写Mapper
映射文件了。我们先围绕一些基本的CRUD来学习，再学习复杂映射多表操作。
@Insert：实现新增
@Update：实现更新
@Delete：实现删除
@Select：实现查询
@Result：实现结果集封装
@Results：可以与@Result 一起使用，封装多个结果集
@One：实现一对一结果集封装
@Many：实现一对多结果集封装

 

我们完成简单的user表的增删改查的操作

    private UserMapper mapper;

    @Before
    public void before() throws IOException {
        InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        mapper = sqlSession.getMapper(UserMapper.class);
    }

 

    @Test
    public void testSave(){
        User user = new User();
        user.setUsername("tom");
        user.setPassword("abc");
        mapper.save(user);
    }

    @Test
    public void testUpdate(){
        User user = new User();
        user.setId(8);
        user.setUsername("lucy");
        user.setPassword("123");
        mapper.update(user);
    }

    @Test
    public void testDelete(){
        mapper.delete(9);
    }

    @Test
    public void testFindById(){
        User user = mapper.findById(2);
        System.out.println(user);
    }

    @Test
    public void testFindAll(){
        List<User> all = mapper.findAll();
        for (User user : all) {
            System.out.println(user);
        }
    }

 

1.3 MyBatis的注解实现复杂映射开发
实现复杂关系映射之前我们可以在映射文件中通过配置<resultMap>来实现，使用注解开发后，我们可以使用@Results注解
，@Result注解，@One注解，@Many注解组合完成复杂关系的配置

 

 

 

 

UserMapper

public interface UserMapper {

    @Insert("insert into user values(#{id},#{username},#{password},#{birthday})")
    public void save(User user);

    @Update("update user set username=#{username},password=#{password} where id=#{id}")
    public void update(User user);

    @Delete("delete from user where id=#{id}")
    public void delete(int id);

    @Select("select * from user where id=#{id}")
    public User findById(int id);

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

    @Select("select * from user")
    @Results({
            @Result(id=true ,column = "id",property = "id"),
            @Result(column = "username",property = "username"),
            @Result(column = "password",property = "password"),
            @Result(
                    property = "orderList",
                    column = "id",
                    javaType = List.class,
                    many = @Many(select = "com.itheima.mapper.OrderMapper.findByUid")
            )
    })
    public List<User> findUserAndOrderAll();


    @Select("SELECT * FROM USER")
    @Results({
            @Result(id = true,column = "id",property = "id"),
            @Result(column = "username",property = "username"),
            @Result(column = "password",property = "password"),
            @Result(
                    property = "roleList",
                    column = "id",
                    javaType = List.class,
                    many = @Many(select = "com.itheima.mapper.RoleMapper.findByUid")
            )
    })
    public List<User> findUserAndRoleAll();


}

 

OrderMapper

    @Select("select * from orders where uid=#{uid}")
    public List<Order> findByUid(int uid);



    @Select("select * from orders")
    @Results({
            @Result(column = "id",property = "id"),
            @Result(column = "ordertime",property = "ordertime"),
            @Result(column = "total",property = "total"),
            @Result(
                    property = "user", //要封装的属性名称
                    column = "uid", //根据那个字段去查询user表的数据
                    javaType = User.class, //要封装的实体类型
                    //select属性 代表查询那个接口的方法获得数据
                    one = @One(select = "com.itheima.mapper.UserMapper.findById")
            )
    })
    public List<Order> findAll();

 

RoleMapper

public interface RoleMapper {

    @Select("SELECT * FROM sys_user_role ur,sys_role r WHERE ur.roleId=r.id AND ur.userId=#{uid}")
    public List<Role> findByUid(int uid);

}