彈簧數據wth ne04j錯誤...檢索路徑時出錯

Question

我在neo4j中使用彈簧數據。

我以前@Query標註放置查詢資料庫中的查詢是如下

@Query(value = "START me=node({0}), friend=node({1}) " 
      + "MATCH p=shortestPath(me-[:ACTIVEFRIEND*..]->friend)" 
      + " RETURN p") 

public Iterable<EntityPath<User, User>> getShortestPathBetween(User a, User b); 

在控制器我訪問它作爲

Iterable<EntityPath<User, User>> shortestPathBetween = this.queryService.getShortestPathBetween(user, friend); 
     for (EntityPath<User, User> path : shortestPathBetween) { 
      Iterator<User> iter = path.<User>nodeEntities().iterator(); 
     } 

當它試圖訪問path.nodeEntities，它導致此錯誤：

nested exception is java.lang.NullPointerException] with root cause
java.lang.NullPointerException
at org.springframework.data.neo4j.support.path.ConvertingEntityPath.nodes(ConvertingEntityPath.java:137)
at org.springframework.data.neo4j.support.path.ConvertingEntityPath.nodeEntities(ConvertingEntityPath.java:69)
at com.laindain.cms.controller.QueryController.getShortestPathBetween(QueryController.java:194)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:601) at org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:212) at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:126) at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:96) at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:617) at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:578) at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:900) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:827) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882) at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:789) at javax.servlet.http.HttpServlet.service(HttpServlet.java:647) at javax.servlet.http.HttpServlet.service(HttpServlet.java:728) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99) at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:936) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407) at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1004) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589) at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:1822) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) at java.lang.Thread.run(Thread.java:722)

我會升值吃了，如果有人可以幫助我這一點。

感謝 與Hemant

Answer 1

嘗試定義的方法是這樣的：

public EndResult<EntityPath<User, User>> getShortestPathBetween(User a, User b); 

因爲查詢返回的路徑，而不是路徑的集合。 你可以得到如下結果：

EntityPath<User, User> shortestPathBetween = 
this.queryService.getShortestPathBetween(user, friend).to(EntityPath); 

路徑上的節點和關係，然後可以使用該nodeEntities訪問（）和relationshipEntities（）方法對返回EntityPath。