mybatis 延迟加载的深入理解

  <settings>
    <setting name ="aggressiveLazyLoading" value="false"/>
    <!--开启延迟加载-->
    <setting name="lazyLoadingEnabled" value="true"/>
  </settings>

<!--userMapper.xml-->

....
<resultMap id="BaseResultMap" type="com.redstar.basemapper.pojo.User">
    <id column="id" jdbcType="VARCHAR" property="id"/>
    <result column="name" jdbcType="VARCHAR" property="name"/>
    <result column="age" jdbcType="INTEGER" property="age"/>
    <result column="role_id" jdbcType="INTEGER" property="roleId"/>
  </resultMap>
  <resultMap id="userRoleMapSelect" type="com.redstar.basemapper.pojo.UserVo">
    <association property="user" resultMap="BaseResultMap"/>
    <association property="role" fetchType="lazy" column="{id=role_id}"
           select="com.redstar.basemapper.dao.RoleMapper.getRoleById"/>
  </resultMap>
  <sql id="Base_Column_List">
  id, `name`, age, role_id
 </sql>
  <select id="getUserVo" resultMap="userRoleMapSelect">
   select * from user where id=#{userId}
  </select>
...
  
  
  
  <!--roleMapper.xml-->
...  
  <resultMap id="BaseResultMap" type="com.redstar.basemapper.pojo.Role">
  <id column="id" jdbcType="INTEGER" property="id" />
  <result column="role_name" jdbcType="VARCHAR" property="roleName" />
 </resultMap>
 <sql id="Base_Column_List">
  id, role_name
 </sql>
 <select id="getRoleById" resultMap="BaseResultMap">
  select * from role where id=#{id}
 </select>
... 

@RunWith(SpringRunner.class)
@SpringBootTest
public class BaseMapperApplicationTests {
  @Autowired
  private UserMapper userMapper;

  @Autowired
  private RoleMapper roleMapper;

  @Test
  public void getUserVo() {
    System.out.println(userMapper.getUserVo("12312232"));
//    System.out.println(userMapper.getUserById("12312232"));
//    System.out.println(roleMapper.getRoleById(1));

  }
}