My spring-web version is 5.2.8.RELEASE.

java.lang.NullPointerException: null
 at org.springframework.http.server.ServletServerHttpResponse.lambda$writeHeaders$0(ServletServerHttpResponse.java:103)
 at java.base/java.util.Map.forEach(Map.java:661)
 at org.springframework.http.server.ServletServerHttpResponse.writeHeaders(ServletServerHttpResponse.java:102)
 at org.springframework.http.server.ServletServerHttpResponse.flush(ServletServerHttpResponse.java:89)
 at org.springframework.web.servlet.mvc.method.annotation.HttpEntityMethodProcessor.handleReturnValue(HttpEntityMethodProcessor.java:222)
 at org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:82)
 at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:123)
 at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:878)
 at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:792)
 at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
 at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040)
 at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
 at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
 at org.springframework.web.servlet.FrameworkServlet.doPut(FrameworkServlet.java:920)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:655)
 at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
 at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
 at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:320)
 at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:126)
 at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:90)
 at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334)
 at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:118)
 at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334)
 at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:137)
 at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334)
 at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:111)
 at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334)
 at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:158)
 at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334)
 at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:63)
 at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334)
 at org.springframework.security.oauth2.provider.authentication.OAuth2AuthenticationProcessingFilter.doFilter(OAuth2AuthenticationProcessingFilter.java:176)
 at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334)
 at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:116)
 at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334)
 at org.springframework.web.filter.CorsFilter.doFilterInternal(CorsFilter.java:92)
 at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
 at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334)
 at org.springframework.security.web.header.HeaderWriterFilter.doHeadersAfter(HeaderWriterFilter.java:92)
 at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:77)
 at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
 at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334)
 at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:105)
 at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334)
 at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:56)
 at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
 at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334)
 at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:215)
 at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:178)
 at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:358)
 at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:271)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
 at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)
 at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
 at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)
 at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
 at org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter.doFilterInternal(WebMvcMetricsFilter.java:93)
 at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
 at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
 at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
 at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
 at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
 at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541)
 at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
 at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
 at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
 at org.apache.catalina.valves.RemoteIpValve.invoke(RemoteIpValve.java:747)
 at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
 at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:373)
 at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
 at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)
 at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1589)
 at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
 at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
 at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
 at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
 at java.base/java.lang.Thread.run(Thread.java:834)

Comment From: bclozel

Please share a minimal, sample application that reproduces the problem. Ideally something we can git clone or unzip and run. You can use start.spring.io to create a new project and only add the requires dependencies to reproduce the problem.

Thanks!

Comment From: Tao-Zhang-Myob

Sorry, I was wrong. it's not for RestTemplate. It's for MVC. here is my code implementation:

@RequestMapping(path = "/business/**")
    public ResponseEntity<JsonNode> handleRequest(@RequestBody(required = false) String requestBody,
                                                  HttpMethod method,
                                                  HttpServletRequest request) {
        var response = myProxyService.proxyRequest(getProxyPath(request), method, requestBody, getToken(request));
        return new ResponseEntity(response.getBody(), getHeaders(response.getHeaders()), response.getStatusCode());
    }

and this is the value of response: <204,[Date:"Thu, 07 Apr 2022 06:52:16 GMT", Connection:"keep-alive", Vary:"Origin", "Access-Control-Request-Method", "Access-Control-Request-Headers", Pragma:"no-cache", Expires:"0", Cache-Control:"no-cache, no-store, max-age=0, must-revalidate", X-Frame-Options:"DENY", X-XSS-Protection:"1; mode=block", X-Content-Type-Options:"nosniff", Strict-Transport-Security:"max-age=31536000; includeSubDomains", Access-Control-Allow-Origin:"https://xxxx.com", Access-Control-Allow-Credentials:"true", Content-Security-Policy:"default-src 'self'"]>

Did I use a wrong implementation?

Comment From: snicoll

@Tao-Zhang-Myob Brian asked for a sample, not a partial code snippet. Please take the time to build a small project we can use to reproduce the issue. You can share it with us by pushing it to a GitHub repository or by attaching a zip to this issue.

Comment From: Tao-Zhang-Myob

I think I found the root cause. for some reason, there is no value for some header field and we don't know. so that will cause the NPE error in Spring. I think this place could improve for this scenario. Spring Meet NPE when I call RestTemplate.exchange()

Comment From: spring-projects-issues

If you would like us to look at this issue, please provide the requested information. If the information is not provided within the next 7 days this issue will be closed.

Comment From: spring-projects-issues

Closing due to lack of requested feedback. If you would like us to look at this issue, please provide the requested information and we will re-open the issue.