RESTController：返回资源使FetchType.lazy的行为像FetchType.Eager一样

Question

@Entity
public class Company{

    @Id
    private Integer companyId;

    private String name;

    @OneToMany(mappedBy = "company")
    private List<CompanyFund> companyFunds;

}

@Entity
public class CompanyFunds{

    @Id
    private Integer fundId;

    private String name;

  @ManyToOne(fetch = FetchType.LAZY)
  @JoinColumn(name = "company_id")
  private Company company;

}

//controller
@GetMapping(value = "/{companyId}")
public Resource<Company> find(@PathVariable Integer companyId) {

  Resource<Company> companyResource = companyService.find(companyId);
  return companyResource;
}

//service
public Resource<CompanyTypeOther> find(Integer companyId) {
  Company company =  companyRepository.findById(companyId);

  return restResourceAssembler.toResource(company);
}


@Component
public class RestResourceAssembler implements ResourceAssembler<T, Resource<T>> {

    private EntityLinks entityLinks;

    public RestResourceAssembler(EntityLinks entityLinks) {
        this.entityLinks = entityLinks;
    }

    @Override
    public  Resource<T>  toResource(T entity) {
        Resource<T> resource = new Resource<>(entity);
        resource.add(entityLinks.linkToSingleResource(entity.getClass(), entity.getId()).withSelfRel());

        return resource;
    }
}

public class ServletInvocableHandlerMethod extends InvocableHandlerMethod {

  ......

  public void invokeAndHandle(ServletWebRequest webRequest, ModelAndViewContainer mavContainer,
    ........other code
    try {
      this.returnValueHandlers.handleReturnValue(
          returnValue, getReturnValueType(returnValue), mavContainer, webRequest);
    }
    catch (Exception ex) {
      if (logger.isTraceEnabled()) {
        logger.trace(formatErrorForReturnValue(returnValue), ex);
      }
      throw ex;
    }
  }

  .....

}

我注意到的另一件事是，只有在返回资源 时才会出现此问题。如果我从控制器返回company，就不会发生意外情况。懒惰装载很好。

Answer 1

因为我想延迟加载实体，所以一个小的修复/黑客解决了这个问题（从现在开始）。

@JsonIgnore
@OneToMany(mappedBy = "company")
private List<CompanyFund> companyFunds;

@jsonignore防止序列化惰性加载实体。所以我猜杰克逊是这里的罪魁祸首。

这不是一个修复是我的观点，但只是一个黑客做的事情。仍在等待Spring团队的人回复。