Mybatis的CRUD 增删改查

旧城等待， 2021-09-21 15:22 497阅读 0赞

### 目录 ###

*  namespace 命名空间
 *  select
 *  insert
 *  update
 *  delete

Mybatis 官网： [https://mybatis.org/mybatis-3/zh/getting-started.html][https_mybatis.org_mybatis-3_zh_getting-started.html]

# namespace 命名空间 #

namespace绑定一个对应的 Dap/Mapper 接口

<mapper namespace="com.pro.dao.UserMapper">
    
        
        <select id="getUserList" resultType="com.pro.pojo.User">
            select * from user
        </select>
    </mapper>

# select #

查询语句

*  `id`：绑定 namespace 中接口的方法
 *  `resultType`：SQL返回值类型
 *  `parameterType`：参数类型

> 编写接口

// 根据id查询用户
    User getUserById(int id);

> 编写SQL

<select id="getUserById" resultType="com.pro.pojo.User" parameterType="int">
        select * from user where id = #{id}
    </select>

> 测试

@Test // 根据id查询用户
    public void getUserById() { 
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
    
        User user = mapper.getUserById(1);
        System.out.println("getUserById --> " + user);
    
        // 关闭资源
        sqlSession.close();
    }

# insert #

增删改操作都差不多，这里就演示 `insert`，`update` 和`delete` 就只写了 `SQL`

**注意点：增删改需要提交事务**

> 接口

// 新增用户
    int addUser(User user);

> SQL

<insert id="addUser" parameterType="com.pro.pojo.User">
        insert into user(name,pwd) values(#{name},#{pwd})
    </insert>

> 测试

@Test // 新增用户
    public void addUser() { 
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
    
        User user = new User(0, "test", "123456");
        int test = mapper.addUser(user);
    
        // 提交事务
        sqlSession.commit();
        sqlSession.close();
    }

# update #

**需要提交事务**

<update id="updateUserById" parameterType="com.pro.pojo.User">
        update user set name = #{name}, pwd = ${pwd} where id = #{id}
    </update>

# delete #

**需要提交事务**

<delete id="deleteUserById" parameterType="int">
        delete from user where id = #{id}
    </delete>

[https_mybatis.org_mybatis-3_zh_getting-started.html]: https://mybatis.org/mybatis-3/zh/getting-started.html