《Mybatis入门到精通》——5.基于注解的CRUD

迈不过友情╰ 2023-09-30 03:27 9阅读 0赞

#### Day\_06 ####

Mybatis注解的用法；不推荐使用；  
与XML类似，不再XML中写SQL，改成在接口的方法的注解里写SQL；用法类似；

**1. 不使用XML而是使用@注解在IDAO的方法上面，定义SQL语句**

目录结构没有IDAO接口的XML

![48f8c457332f76aace284354b2f851a5.png][]

**2. 定义CRUD方法**

IUserDao接口

/**
     * @author A
     * User的持久层接口
     */
    //开启二级缓存 @CacheNamespace(blocking = true)
    
    @CacheNamespace(blocking = true)
    public interface IUserDao {
        /**
         * 查询所有User表的记录-操作
         * @return
         */
        @Select("SELECT * FROM user")
        List<User> findAll();
    
        /**
         * 保存用户
         * @param user
         */
        @Insert("insert into user(username,address,sex,birthday)values(#{username},#{address},#{sex},#{birthday})")
        void saveUser(User user);
    
        /**
         * 更新用户
         * @param user
         */
        @Update("update user set username=#{username},sex=#{sex},birthday=#{birthday},address=#{address} where id=#{id}")
        void updateUser(User user);
    
        /**
         * 删除用户
         * @param userId
         */
        @Delete("delete from user where id=#{id} ")
        void deleteUser(Integer userId);
    
        /**
         * 根据id查询用户
         * @param userId
         * @return
         */
        @Select("select * from user  where id=#{id} ")
        User findById(Integer userId);
    
        /**
         * 根据用户名称模糊查询
         * @param username
         * @return
         * //    @Select("select * from user where username like #{username} ")
         */
        @Select("select * from user where username like '%${value}%' ")
        List<User> findUserByName(String username);
    
        /**
         * 查询总用户数量
         * @return
         */
        @Select("select count(*) from user ")
        int findTotalUser();
    }

**3. 一对一、一对多查询**

//添加resultMap（因为多了List<Account>属性），一对一/多
    
    /**
     * 查询所有用户：一对多
     * @return
     */
    @Select("select * from user")
    @Results(id="userMap",value={
            @Result(id=true,column = "id",property = "userId"),
            @Result(column = "username",property = "userName"),
            @Result(column = "address",property = "userAddress"),
            @Result(column = "sex",property = "userSex"),
            @Result(column = "birthday",property = "userBirthday"),
            @Result(property = "accounts",column = "id",
                    many = @Many(select = "com.ming.dao.IAccountDao.findAccountByUid",
                            fetchType = FetchType.LAZY))
    })
    List<User> findAll1();
    
    /**
     * 根据id查询用户
     * @param userId
     * @return
     */
    @Select("select * from user  where id=#{id} ")
    @ResultMap("userMap")
    User findById1(Integer userId);
    
    /**
     * 根据用户名称模糊查询
     * @param username
     * @return
     */
    @Select("select * from user where username like #{username} ")
    @ResultMap("userMap")
    List<User> findUserByName1(String username);

**4. 注解开启二级缓存**

哪个IDao接口需要就写在哪儿；写在接口上面；

@CacheNamespace(blocking = true)

[48f8c457332f76aace284354b2f851a5.png]: https://img-blog.csdnimg.cn/img_convert/48f8c457332f76aace284354b2f851a5.png