JPARepository僅返回單個字段

我想返回特定的字段僅用於服務。所以，我在JPARepository接口寫下面的代碼：JPARepository僅返回單個字段

@Query(value="select r.id from Ride r") 
public List<Ride> findIdOnly();

但是當我通過打這個方法：

http://localhost:8080/api/sdr/rides/search/findIdOnly

它給下面的異常回報。我搜索但JPARepository我只喜歡這個解決方案，它是不工作：

java.lang.IllegalArgumentException: PersistentEntity must not be null! 
    at org.springframework.util.Assert.notNull(Assert.java:115) 
    at org.springframework.data.rest.webmvc.PersistentEntityResource$Builder.<init>(PersistentEntityResource.java:139) 
    at org.springframework.data.rest.webmvc.PersistentEntityResource$Builder.<init>(PersistentEntityResource.java:122) 
    at org.springframework.data.rest.webmvc.PersistentEntityResource.build(PersistentEntityResource.java:114) 
    at org.springframework.data.rest.webmvc.PersistentEntityResourceAssembler.wrap(PersistentEntityResourceAssembler.java:102) 
    at org.springframework.data.rest.webmvc.PersistentEntityResourceAssembler.toResource(PersistentEntityResourceAssembler.java:83) 
    at org.springframework.data.rest.webmvc.AbstractRepositoryRestController.entitiesToResources(AbstractRepositoryRestController.java:143) 
    at org.springframework.data.rest.webmvc.AbstractRepositoryRestController.toResources(AbstractRepositoryRestController.java:90) 
    at org.springframework.data.rest.webmvc.AbstractRepositoryRestController.toResource(AbstractRepositoryRestController.java:110) 
    at org.springframework.data.rest.webmvc.RepositorySearchController.executeSearch(RepositorySearchController.java:185) 
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) 
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) 
    at java.lang.reflect.Method.invoke(Method.java:483) 
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221) 
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136) 
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110) 
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:832) 
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:743) 
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) 
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:961) 
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:895) 
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:967) 
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:858) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:620) 
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:843) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:727) 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303) 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) 
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241) 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) 
    at com.org.qatarcreations.saeeq.mvc.web.config.MvcConfig$CORSFilter.doFilterInternal(MvcConfig.java:149) 
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241) 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:316) 
    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:126) 
    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:90) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:114) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:122) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:111) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:169) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:48) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.authentication.www.BasicAuthenticationFilter.doFilterInternal(BasicAuthenticationFilter.java:158) 
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:120) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:64) 
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:91) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:53) 
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) 
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:213) 
    at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:176) 
    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:346) 
    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:262) 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241) 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) 
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:121) 
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241) 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) 
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220) 
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122) 
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501) 
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170) 
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98) 
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116) 
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408) 
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040) 
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607) 
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1721) 
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1679) 
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) 
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) 
    at java.lang.Thread.run(Thread.java:745)

來源

2016-09-08 apurv

你有沒有註冊所需的所有豆？ – nowszy94

查詢返回只有一個字段，但你的方法返回的RideList。嘗試改變的List型，將id場

來源

2016-09-08 06:46:48

卜如果我想返回一個字段，該怎麼辦？像 @Query（value =「select r.id，r fromfrom from the position from ride」） public List findIdOnly（）; – apurv

爲什麼不只是返回對象並讓調用代碼決定如何處理它呢？ – christopher

然後，您可以將其更改爲列表。 –

您可以使用投影

預測聲明的基礎類型和相關暴露性質的方法簽名之間的合同。因此，需要根據基礎類型的屬性名稱來命名getter方法。

http://docs.spring.io/spring-data/jpa/docs/current/reference/html/#projections

來源

2016-09-08 09:13:21

@Query（值=「選擇r.fromLatitude from Ride r「） \t public List findFromLatitudeOnly（）; \t \t 公共接口FromLatitude \t { \t \t公共雙getFromLatitude（）; \t}' 這也給出同樣的錯誤 – apurv

感謝你們幫助我。最後我找到了答案，這不正是我期待的但接近的答案。

@Query("select new com.org.qatarcreations.saeeq.model.Ride(d.fromLatitude) from Ride d") 
public List<Ride> findRidesForListing();

所以，當我打：

http://localhost:8080/api/sdr/rides/search/findRidesForListing

響應：

{ 
    "links" : [ { 
    "rel" : "self", 
    "href" : "http://localhost:8080/api/sdr/rides/search/findRidesForListing" 
    } ], 
    "content" : [ { 
    "country" : null, 
    "service" : null, 
    "price" : null, 
    "finalPrice" : null, 
    "vehicle" : null, 
    "rideMapShape" : null, 
    "customerRating" : null, 
    "status" : null, 
    "driver" : null, 
    "fromLongitude" : 0.0, 
    "fromLatitude" : 75.546546, 
    "toLongitude" : 0.0, 
    "driverRating" : null, 
    "toLatitude" : 0.0, 
    "customer" : null, 
    "fromAddress" : null, 
    "toAddress" : null, 
    "rideEndTime" : null, 
    "rideStartTime" : null, 
    "totalDistance" : null, 
    "cancelReason" : null, 
    "links" : [ { 
     "rel" : "self", 
     "href" : "http://localhost:8080/api/sdr/rides/0" 
    }] 
    } ] 
}

我發現從答案：

https://stackoverflow.com/a/29020641/3576817

來源

2016-09-08 11:59:07 apurv

JPARepository僅返回單個字段

回答

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