如何在 JUnit5 中模拟 MapStruct 嵌套映射器

Question

我已经寻找解决方案大约一天了。我仍然无法给出一个有效的例子。

我的问题很简单。我有一个映射器使用另一个映射器：

@Mapper(componentModel = "spring", uses = {RoleMapper.class})
public interface UserMapper {

    /**
     * Converts User DTO to User JPA Entity
     * @Mapping annotation is used to convert fields with different names
     * @param dto
     * @return
     */
    @Mappings({
            @Mapping(target = "identityNo", source = "dto.userIdentity"),
            @Mapping(target = "role", source = "dto.roleDTO")
    })
    User dtoToEntity(UserDTO dto);

    /**
     * Converts User JPA Entity to User DTO
     * @Mapping annotation is used to convert fields with different names
     * @param entity
     * @return
     */
    @Mappings({
            @Mapping(target = "userIdentity", source = "entity.identityNo"),
            @Mapping(target = "roleDTO", source = "entity.role")
    })
    UserDTO entityToDto(User entity);

}

@Mapper(componentModel = "spring")
public interface RoleMapper {

    Role roleDtoToEntity(RoleDTO dto);
    RoleDTO roleEntityToDto(Role entity);
}

我的测试类测试映射器是否正常工作：

class UserMapperTest {

    private UserMapper mapper = Mappers.getMapper(UserMapper.class);

    @Test
    void dtoToEntity() {

        User user = new User();
        user.setName("john");
        user.setSurname("doe");
        user.setIdentityNo("11111111111");
        user.setRole(new Role("ROLE_ADMIN"));

        UserDTO dto = mapper.entityToDto(user);

        Assertions.assertEquals(user.getName(), dto.getName());
        Assertions.assertEquals(user.getSurname(), dto.getSurname());
        Assertions.assertEquals(user.getIdentityNo(), dto.getUserIdentity());
        Assertions.assertEquals(user.getRole().getName(), dto.getRoleDTO().getName());
    }
}

但是，在自动生成的 impl 类UserMapperImpl中调用 roleMapper 的行上会抛出 NullPointerException ：

这涉及到我的基本问题，如何模拟或自动装配嵌套映射器类？

Answer 1

嵌套映射器为空，因为 Spring 上下文未加载。因此，@Autowired 不起作用。

解决方案是通过 ReflectionTestUtils 注入嵌套映射器。

@InjectMocks
private UserMapper mapper = UserMapperImpl.INSTANCE;

@Before
public void init() {
    RoleMapper roleMapper = Mappers.getMapper(RoleMapper.class);
    ReflectionTestUtils.setField(mapper, "roleMapper", roleMapper);
}