这个异常挺多人遇到的，不过我看了一下，跟我们的情况都不一样。

1.    流没关闭。

2.    未设置响应头。

3.    jsp页面需要清空流。

说一下我们遇到的情况。就是一个简单的sprinboot项目。

用的是springboot 1.5.6，本地启动后用花生壳内网映射。

在用httpclient请求项目接口，会报以下的错误。

1. Forwarding to error page from request [/xxx/xxx] due to exception [getOutputStream() has already been called for this response]（接口项目报这个错）

2. java.io.FileNotFoundException: http://1xxx/xxx/xxx/xxx（httpclient项目报这个错）

信息如下(接口项目):

[ERROR] o.springframework.boot.web.support.ErrorPageFilter - Forwarding to error page from request [/xxx/xxx] due to exception [getOutputStream() has already been called for this response]java.lang.IllegalStateException: getOutputStream() has already been called for this responseat org.apache.catalina.connector.Response.getWriter(Response.java:624)at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:211)at javax.servlet.ServletResponseWrapper.getWriter(ServletResponseWrapper.java:109)at org.thymeleaf.spring4.view.ThymeleafView.renderFragment(ThymeleafView.java:335)at org.thymeleaf.spring4.view.ThymeleafView.render(ThymeleafView.java:190)at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1286)at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1041)at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:984)at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901)at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:872)at javax.servlet.http.HttpServlet.service(HttpServlet.java:661)at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)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:52)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)at com.alibaba.druid.support.http.WebStatFilter.doFilter(WebStatFilter.java:123)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.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:101)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.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:101)at org.springframework.boot.web.support.ErrorPageFilter.doFilter(ErrorPageFilter.java:108)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.ApplicationDispatcher.invoke(ApplicationDispatcher.java:728)at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:467)at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:392)at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:311)at org.springframework.boot.web.support.ErrorPageFilter.handleErrorStatus(ErrorPageFilter.java:149)at org.springframework.boot.web.support.ErrorPageFilter.doFilter(ErrorPageFilter.java:117)at org.springframework.boot.web.support.ErrorPageFilter.access$000(ErrorPageFilter.java:59)at org.springframework.boot.web.support.ErrorPageFilter$1.doFilterInternal(ErrorPageFilter.java:90)at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)at org.springframework.boot.web.support.ErrorPageFilter.doFilter(ErrorPageFilter.java:108)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:478)at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:80)at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:624)at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:799)at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1455)at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)at java.lang.Thread.run(Thread.java:748)

信息如下(客户端请求项目):

java.io.FileNotFoundException: http://1xxx/xxx/xxx/xxxat sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1836)at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1441)at com.ruidou.insurance.utils.HttpUtil.doPost(HttpUtil.java:259)at com.ruidou.insurance.test.InsuranceTest.queryInsurance(InsuranceTest.java:109)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:497)at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:252)at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:94)at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)

问题猜想：

1.     springboot项目配置了thymeleaf模板，由于404请求跳转error.html。

2.     由于没有error.html，导致客户端变成了file找不到。

3.     花生壳映射问题，在服务器好像是没有问题，证明代码没有问题。

解决方式：

1.     检查请求是否404。

2.     关闭thymeleaf的配置。

3.     不要用花生壳。在服务器上如果还出现类似问题，可能就是代码的问题了。