覆盖 RestController 方法后，我得到：org.springframework.dao.InvalidDataAccessApiUsageException: The given id must not be null

Question

我想将 spring-hateoas 添加到我的投资组合项目中并使其完整 restful。这意味着我需要覆盖 AbstractResource class 给出的方法（这是我的@RestController 的基础 class）来根据我的需要编辑它，当我这样做时我得到 org.springframework.dao.InvalidDataAccessApiUsageException：给定的 ID 不能为空！

我的项目如下所示：

服务包

public interface AbstractService<ENTITY extends AbstractEntity> {

    ENTITY update(ENTITY entity);

    EntityModel<ENTITY> getById(Long id);

    ENTITY save(ENTITY entity);

    void delete(Long id);

    Collection<ENTITY> getAll();
}

public abstract class AbstractServiceImpl<ENTITY extends AbstractEntity> implements AbstractService<ENTITY> {

    protected abstract JpaRepository<ENTITY, Long> getRepository();

    @Override
    public Collection<ENTITY> getAll() {
        return getRepository().findAll();
    }

    @Override
    public EntityModel<ENTITY> getById(Long id) {
        return EntityModel.of(getRepository().getOne(id));
    }
}

@Service
public class UserServiceImpl extends AbstractServiceImpl<User> implements UserService {

    private final UserRepository userRepository;

    @Override
    protected JpaRepository<User, Long> getRepository() {
        return userRepository;
    }
}

资源包

public abstract class AbstractResource<ENTITY extends AbstractEntity>{

    public abstract AbstractService<ENTITY> getService();

    @GetMapping(value = "/{id}", produces = {"application/hal+json"})
    public EntityModel<ENTITY> getById(@PathVariable("id") Long id) {
        return getService().getById(id);
    }

    @GetMapping
    public Collection<ENTITY> getAll() {
        return getService().getAll();
    }
}

当我这样离开时 - 一切正常 - 我得到了预期的回复

@RestController
@RequestMapping("/api/users")
public class UserResource extends AbstractResource<User> {

    @Autowired
    private final UserService userService;

    @Override
    public AbstractService<User> getService() {
        return userService;
    }
}

当我尝试覆盖此方法时发生错误

@RestController
@RequestMapping("/api/users")
public class UserResource extends AbstractResource<User> {

    @Autowired
    private final UserService userService;

    @Override
    public AbstractService<User> getService() {
        return userService;
    }

    @Override
    public EntityModel<User> getById(Long id) {
        return userService.getById(id);
        or
        return super.getById(id);
    }
}

Answer 1

UserResource覆盖AbstractResource.getById(Long)后，虽然继承了注解@GetMapping(value = "/{id}", produces = {"application/hal+json"})，但没有继承注解@PathVariable("id")。将注释 @PathVariable("id") 放在 UserResource.getById(Long) 内应该可以解决您的问题。

强烈建议在Github中放置一个可运行的示例项目（包括请求URL和测试数据）以重现您遇到的错误。否则很难查明原因和验证。

覆盖 RestController 方法后，我得到：org.springframework.dao.InvalidDataAccessApiUsageException: The given id must not be null

After overriding RestController method I get: org.springframework.dao.InvalidDataAccessApiUsageException: The given id must not be null

java

spring-data-jpa

spring-data

spring-hateoas