spring mvc处理http请求报错:java.lang.IllegalStateException: getInputStream() has already been called for this request
发送 post 请求到 controller 处理失败，报错日志如下：
java.lang.IllegalStateException: getInputStream() has already been called for this request at org.apache.catalina.connector.Request.getReader(Request.java:1212)at org.apache.catalina.connector.RequestFacade.getReader(RequestFacade.java:504) 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:498) at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221) at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136) at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110) at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:832) at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:743) at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:961) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:895) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:967) at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:869) at javax.servlet.http.HttpServlet.service(HttpServlet.java:661) at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:843) at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:230) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) at org.apache.logging.log4j.web.Log4jServletFilter.doFilter(Log4jServletFilter.java:71) 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.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:341) at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:799) at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:861) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1455) at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java: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) 四月 26, 2017 6:27:40 下午 org.apache.catalina.core.StandardWrapperValve invoke 严重: Servlet.service()for servlet [service-dispatcher] in context with path [] threw exception [Request processing failed; nested exception is java.lang.IllegalStateException: getInputStream() has already been called for this request] with root cause java.lang.IllegalStateException: getInputStream() has already been called for this request at org.apache.catalina.connector.Request.getReader(Request.java:1212) at org.apache.catalina.connector.RequestFacade.getReader(RequestFacade.java:504) 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:498) at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221) at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136) at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110) at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:832) at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:743) at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:961) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:895) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:967) at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:869) at javax.servlet.http.HttpServlet.service(HttpServlet.java:661) at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:843) at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:230) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) at org.apache.logging.log4j.web.Log4jServletFilter.doFilter(Log4jServletFilter.java:71) 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.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:341) at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:799) at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:861) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1455) at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java: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)
从报错信息看是调用了两次 ServletRequest 的 getInputStream()，但实际上 getInputStream() 和 getReader()只能调用一次，第二次无论是再调哪个都报错，也就是请求消息体只能读取一次。代码跟 debug 调试，发现是入参 json 转换时调用 ServletRequest 的子类 HttpServletRequest 的 getReader() 时报错了：
JsonFormat.parser().merge(request.getReader(), builder);
那么前面肯定有地方调用了 getInputStream()，找了半天发现是 spring mvc 的注解 @RequestBody
@RequestMapping(value = "/{service}/{method}", method = {RequestMethod.GET, RequestMethod.POST})
public @ResponseBody void invoke(@PathVariable("service") String service, @PathVariable("method") String method,
HttpServletRequest request, HttpServletResponse response, @RequestBody String data)
@RequestBody 里需要以流的形式读取请求，具体见 spring 源码 AbstractJsonHttpMessageConverter 类 getReader 方法：
private static Reader getReader(HttpInputMessage inputMessage) throws IOException { return new InputStreamReader(inputMessage.getBody(), getCharset(inputMessage.getHeaders())); }
这里读流一次后，后面就无法再次读流了。