ERROR: getWriter() has already been called for this response in springmvc

Question

When building a rest web service using Spring Mvc in SpringBoot project, exceptions eccured as below:

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)

However, the rest service functions well, and can be called and return expected results. Here is the code block where i call the method 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();
    }
}

I have viewed many concerned questions and corresponding answers, but none of them really suits my problem. Looking forward to your comments. Thanks!

Answer 1

Add response.reset(); before using response.

example:

response.reset();
response.getOutputStream();

Answer 2

You can see in stack trace HandlerMethodReturnValueHandlerComposite, this means something is returning a response to Spring "handler".

Then Spring uses the AbstractJackson2HttpMessageConverter to convert the returned value.

So I guess the problem is not in this method, please inspect or post here all your controller code at least.