mybatis的collection建立1对多关系

association用于1对1, 想不出有什么是1对1的, 如果1对1能不能他娘的直接一个表搞定了?

collection用于1对多, model里面有个list,例如user类里面有个roleList:

    private List<SysRole> roleList;

在mapper的xml里面, 首先是extends原本的resultMap

    <resultMap id="userRoleListMap" extends="userMap"  type="marc.mybatis.lesson1.model.SysUser">
        <collection property="roleList" columnPrefix="role_" resultMap="marc.mybatis.lesson1.mapper.SysRoleMapper.roleMap" />
    </resultMap>

至于userMap是这样的.

    <resultMap id="userMap" type="marc.mybatis.lesson1.model.SysUser">
        <id property="id" column="id" />
        <result property="userName" column="user_name" />
        <result property="userPassword" column="user_password" />
        <result property="userEmail" column="user_email" />
        <result property="userInfo" column="user_info" />
        <result property="headImg" column="head_img" jdbcType="BLOB" />
        <result property="createTime" column="create_time" jdbcType="TIMESTAMP" />
    </resultMap>

而roleMap是在另一个mapper的xml文件里面:

    <resultMap id="roleMap" type="marc.mybatis.lesson1.model.SysRole">
        <id property="id" column="id" />
        <result property="roleName" column="role_name" />
        <result property="enabled" column="enabled" />
        <result property="createBy" column="create_by" />
        <result property="createTime" column="create_time" jdbcType="TIMESTAMP" />
    </resultMap>

就这么简单, 加上service的interface之后就可以测试了:

    SysUser selectUserRoleListMap(@Param("id") Long id);

测试类如下, 省略baseTester:

    @Test
    public void testSelectUserRoleListMap() {
        SqlSession sqlSession = getSqlSession();
        try {
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
            SysUser resultUser = userMapper.selectUserRoleListMap(1L);
            System.out.println(resultUser);
        } finally {
            sqlSession.close();
        }
    }

哦, 忘了贴xml里面的select了

    <select id="selectUserRoleListMap" resultMap="userRoleListMap">
        select
        u.id,
        u.user_name,
        u.user_password,
        u.user_email,
        u.user_info,
        u.head_img,
        u.create_time,
        r.id role_id,
        r.role_name role_role_name,
        r.enabled
        role_enabled,
        r.create_by role_create_by,
        r.create_time
        role_create_time
        from sys_user u
        inner join
        sys_user_role
        ur on u.id =
        ur.user_id
        inner join
        sys_role r on
        ur.role_id
        = r.id
        where
        u.id = #{id}
    </select>

滑稽的地方是, role_role_name, 太特么不优雅了...一开始role表的字段就不应该叫role_name, 傻...