BŁĄD: Funkcja getWriter () została już wywołana dla tej odpowiedzi w springmvc - spring, spring-mvc, spring-boot

Podczas budowania pozostałej usługi sieci Web przy użyciu Spring Mvc w projekcie SpringBoot wyjątki zostały określone poniżej:

2017-05-24 10:16:10.849 ERROR 10 --- [io-8080-exec-89] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet dispatcherServlet threw exception
java.lang.IllegalStateException: getWriter() has already been called for this response
at org.apache.catalina.connector.Response.getOutputStream(Response.java:575)
at org.apache.catalina.connector.ResponseFacade.getOutputStream(ResponseFacade.java:194)
at javax.servlet.ServletResponseWrapper.getOutputStream(ServletResponseWrapper.java:100)
at org.springframework.http.server.ServletServerHttpResponse.getBody(ServletServerHttpResponse.java:89)
at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.writeInternal(AbstractJackson2HttpMessageConverter.java:237)
at org.springframework.http.converter.AbstractGenericHttpMessageConverter.write(AbstractGenericHttpMessageConverter.java:100)
at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:232)
at org.springframework.web.servlet.mvc.method.annotation.HttpEntityMethodProcessor.handleReturnValue(HttpEntityMethodProcessor.java:198)
at org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:81)
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:130)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:963)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:622)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:230)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:101)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:101)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:101)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:101)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:101)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:101)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:726)
at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:592)
at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:526)
at org.apache.catalina.core.StandardHostValve.custom(StandardHostValve.java:389)
at org.apache.catalina.core.StandardHostValve.status(StandardHostValve.java:254)
at org.apache.catalina.core.StandardHostValve.throwable(StandardHostValve.java:349)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:175)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:349)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:1110)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:785)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1425)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:745)

Jednak pozostałe usługi działają dobrze i można je wywoływać i zwracać oczekiwane wyniki. Oto blok kodu, w którym wywołuję metodę getWritter ():

@RequestMapping(value = "/kafka/picfile", method = RequestMethod.POST)
public void uploadPicture(HttpServletResponse response) {
String result = "";
response.reset();
response.setCharacterEncoding("utf-8");
PrintWriter writer = null;
String prefix = "<!DOCTYPE html>n" +
"<html lang="en">n" +
"<head>n" +
"</head>n" +
"<body>";
String suffix = "</body>n" +
"</html>";
try {
writer = response.getWriter();
Picture picture = new Picture("testname", "this is a test picture");
result = kafkaService.send(picture);
if(!"success".equals(result)){
result = "error[xxxxxxxxxxxxx]";
}
} catch (Exception e) {
result = "error["+e.getMessage()+"]";
}
result = prefix+"n"+result+"n"+suffix;
if(writer != null){
writer.write(result);
writer.flush();
writer.close();
}
}

Obejrzałem wiele zainteresowanych pytań i odpowiadających odpowiedzi, ale żadne z nich tak naprawdę nie pasuje do mojego problemu. Czekam na twoje komentarze. Dzięki!

Odpowiedzi:

Dodaj response.reset (); przed użyciem odpowiedzi.

przykład:

response.reset();
response.getOutPoutStream();

Możesz zobaczyć ślad stosu HandlerMethodReturnValueHandlerComposite, oznacza to, że coś zwraca odpowiedź na „moduł obsługi” Springa.

Następnie Spring używa AbstractJackson2HttpMessageConverter przekonwertować zwróconą wartość.

Myślę, że problem nie dotyczy tej metody, sprawdź lub opublikuj tutaj przynajmniej cały kod kontrolera.