Iterator - Spring MVC控制器中的java.util.NoSuchElementException

Question

我有Java spring MVC应用程序。

通过AngularJS。从我的客户端上传单个文件以及我发布到服务器的其他一些数据。

我的Java Controller类

@Controller 
public class FileUploadController { 

    @RequestMapping(value="/fileUpload", method = RequestMethod.POST) 
    public void UploadFile(MultipartHttpServletRequest request, HttpServletResponse response) { 
     System.out.println(request.getFileNames()); 
     Iterator<String> itr=request.getFileNames(); 
     System.out.println(itr.hashCode()); 
     MultipartFile file=request.getFile(itr.next()); 
     String fileName=file.getOriginalFilename(); 
     System.out.println(fileName); 
      } 
} 

当我运行此我得到的印刷头两行，然后让异常。

[email protected] 
1190767452 

错误

java.util.NoSuchElementException 
    at java.util.LinkedHashMap$LinkedHashIterator.nextEntry(LinkedHashMap.java:396) 
    at java.util.LinkedHashMap$KeyIterator.next(LinkedHashMap.java:405) 
    at com.uploaddemo.web.FileUploadController.UploadFile(DocumentUploadController.java:21) 
    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:606) 
    at org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:219) 
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:132) 
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104) 
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:745) 
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:686) 
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80) 
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:925) 
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856) 
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:920) 
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:827) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:647) 
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:801) 
    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:502) 
    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:953) 
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118) 
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408) 
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1023) 
    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:1145) 
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) 
    at java.lang.Thread.run(Thread.java:744) 

这意味着什么？是服务器获取文件还是在服务器控制器我做错了？

因为当我打印迭代器的散列码时，它会打印出来，这意味着它不为空（如果我错了，请纠正我）。

我正在从客户端发送文件和其他数据。

Answer 1

我想你的请求中没有文件。 getFileNames永远不会返回null：如果没有文件，它是空集合上的迭代器。要知道是否有文件，可以调用itr.hasNext（）。