【发布时间】：2014-05-31 11:15:09
【问题描述】：
我创建了一个简单的存储库，其中包含我系统中的所有人员，一切似乎都运行良好。我可以根据给定的键和值添加、删除甚至检索单个人员，但由于某种原因，我无法直接检索存储在存储库中的所有人员。我尝试使用 findAll() 方法来做到这一点，该方法应该返回一个可迭代的。然后我尝试使用可迭代对象进行迭代，并将每个人存储在我希望函数返回的数组列表中。
public List<Person> getAllPersons() {
Iterable<Person> p = personRepository.findAll();
System.out.println("person count: " + personRepository.count());
List<Person> persons = new ArrayList<Person>();
for (Person person : p) {
System.out.println("person");
persons.add(person);
}
return persons;
}
打印行打印“3”，所以存储库不是空的，但我仍然在下面的错误中得到一个空指针异常。
apr 16, 2014 3:45:54 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet [bmsapp] in context with path [/bmsapp] threw exception [Request processing failed; nested exception is org.neo4j.graphdb.TransactionFailureException: Failed to mark transaction as rollback only.] with root cause
java.lang.NullPointerException
at org.neo4j.kernel.TopLevelTransaction.markAsRollbackOnly(TopLevelTransaction.java:93)
at org.neo4j.kernel.TopLevelTransaction.failure(TopLevelTransaction.java:86)
at org.neo4j.cypher.internal.spi.v2_0.TransactionBoundExecutionContext.close(TransactionBoundExecutionContext.scala:58)
at org.neo4j.cypher.internal.compiler.v2_0.spi.DelegatingQueryContext.close(DelegatingQueryContext.scala:32)
at org.neo4j.cypher.internal.compiler.v2_0.spi.ExceptionTranslatingQueryContext.org$neo4j$cypher$internal$compiler$v2_0$spi$ExceptionTranslatingQueryContext$$super$close(ExceptionTranslatingQueryContext.scala:34)
at org.neo4j.cypher.internal.compiler.v2_0.spi.ExceptionTranslatingQueryContext$$anonfun$close$1.apply$mcV$sp(ExceptionTranslatingQueryContext.scala:34)
at org.neo4j.cypher.internal.compiler.v2_0.spi.ExceptionTranslatingQueryContext$$anonfun$close$1.apply(ExceptionTranslatingQueryContext.scala:34)
at org.neo4j.cypher.internal.compiler.v2_0.spi.ExceptionTranslatingQueryContext$$anonfun$close$1.apply(ExceptionTranslatingQueryContext.scala:34)
at org.neo4j.cypher.internal.compiler.v2_0.spi.ExceptionTranslatingQueryContext.org$neo4j$cypher$internal$compiler$v2_0$spi$ExceptionTranslatingQueryContext$$translateException(ExceptionTranslatingQueryContext.scala:149)
at org.neo4j.cypher.internal.compiler.v2_0.spi.ExceptionTranslatingQueryContext.close(ExceptionTranslatingQueryContext.scala:34)
at org.neo4j.cypher.internal.compiler.v2_0.ClosingIterator.failIfThrows(ClosingIterator.scala:94)
at org.neo4j.cypher.internal.compiler.v2_0.ClosingIterator.next(ClosingIterator.scala:45)
at org.neo4j.cypher.internal.compiler.v2_0.PipeExecutionResult.next(PipeExecutionResult.scala:168)
at org.neo4j.cypher.internal.compiler.v2_0.PipeExecutionResult.next(PipeExecutionResult.scala:34)
at scala.collection.Iterator$$anon$11.next(Iterator.scala:328)
at scala.collection.convert.Wrappers$IteratorWrapper.next(Wrappers.scala:30)
at org.neo4j.cypher.internal.compiler.v2_0.PipeExecutionResult$$anon$1.next(PipeExecutionResult.scala:76)
at org.neo4j.helpers.collection.IteratorWrapper.next(IteratorWrapper.java:47)
at org.neo4j.helpers.collection.IteratorWrapper.next(IteratorWrapper.java:47)
at bmsapp.repository.NeoPersonDao.getAllPersons(NeoPersonDao.java:33)
at bmsapp.service.SimplePersonManager.getPersons(SimplePersonManager.java:32)
at bmsapp.web.HelloController.HelloHandler(HelloController.java:45)
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.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:175)
at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:446)
at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:434)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:938)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:870)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:961)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:852)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:837)
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.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:744)
我已经浪费了几个小时来解决这个问题，但没有任何运气。有人可以帮我吗？
【问题讨论】：
-
也许你应该使用
Iterator<Person> it = p.iterator() -
我已经尝试过 Iterator 和 Iterable 选项，但是当我尝试访问它们时都会导致空指针异常。
标签： java spring spring-data spring-data-neo4j