discriminator

• 鉴别器：mybatis可以使用discriminator判断某列的值，然后根据某列的值改变封装行为

• 封装Employee:

  • 如果查出的是女生；就把部门信息查询出来，否则不查询

  • 如果查出的是男生；把last_name这一列的值赋给email

  <resultMap id="MyEmpDis" type="com.atguigu.mybatis.bean.Employee"><id column="id" property="id"></id><result column="last_name" property="lastName"></result><result column="email" property="email"></result><result column="gender" property="gender"></result><!--column:指定判定的列名javaType:列值对应的java类型--><discriminator javaType="string" column="gender"><!--            女生resultType:指定封装的结果类型，不能缺少--><case value="0" resultType="com.atguigu.mybatis.bean.Employee"><association property="dept" select="com.atguigu.mybatis.dao.DepartmentMapper.getDeptById"column="d_id"></association></case><!--            男生--><case value="1" resultType="com.atguigu.mybatis.bean.Employee"><id column="id" property="id"></id><result column="last_name" property="lastName"></result><result column="last_name" property="email"></result><result column="gender" property="gender"></result></case></discriminator></resultMap><!--    public Employee getEmpByIdStep(Integer id);--><select id = "getEmpByIdStep" resultMap="MyEmpDis">select * from tb1_employee where id = #{id}</select>

  @Testpublic void test04() throws IOException {SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();SqlSession sqlSession = sqlSessionFactory.openSession();try{EmployeeMapperPlus mapper = sqlSession.getMapper(EmployeeMapperPlus.class);Employee employee = mapper.getEmpByIdStep(3);System.out.println(employee);System.out.println(employee.getDept());}finally {sqlSession.close();}}