使用jmeter模拟post请求在jforum论坛回帖报错

一.问题描述
1.使用jmeter模拟post请求在jforum论坛回帖报错，检查回帖发现并没有显示新的回帖信息，报错信息如下。
-- BEGIN ERROR STACK TRACE
net.jforum.exceptions.ForumException: java.lang.reflect.InvocationTargetException
at sun.reflect.GeneratedMethodAccessor205.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at net.jforum.Command.process(Command.java:114)
at net.jforum.JForum.processCommand(JForum.java:217)
at net.jforum.JForum.service(JForum.java:200)
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 net.jforum.util.legacy.clickstream.ClickstreamFilter.doFilter(ClickstreamFilter.java:59)
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:97)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143)
at psiprobe.Tomcat90AgentValve.invoke(Tomcat90AgentValve.java:35)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:690)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:888)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1597)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.reflect.InvocationTargetException
... 33 more
Caused by: java.lang.ClassCastException: java.lang.String cannot be cast to net.jforum.util.legacy.commons.fileupload.FileItem
at net.jforum.view.forum.common.AttachmentCommon.preProcess(AttachmentCommon.java:131)
at net.jforum.view.forum.PostAction.insertSave(PostAction.java:1074)
... 33 more

URL is: /jforum-2.1.9/jforum.page?null
END ERROR STACK TRACE--

二.问题分析
1.检查报错信息，提示string字符串不能强制转换为fileupload.FileItem类型，查了一下fileupload.FileItem是java的一个fileupload类，用于文件上传功能，在回帖的网页看了一下，发现有个上传文件的按钮，随便上传了一个图片，用fiddler抓包如下。
Caused by: java.lang.ClassCastException: java.lang.String cannot be cast to net.jforum.util.legacy.commons.fileupload.FileItem

三.解决方案
1.通过对比2次抓包的数据，发现这个file_0不是字符串类型，而是octet-stream或者image/png或者其他application类型，所以需要在post请求里将参数file_0删除后提交，或者如果需要上传文件（比如图片），可以在jmeter的文件上传页签填写对应的信息。

2.根据上面的2种方式修改后，再提交post请求，可以看到网页已经可以正常显示提交的回复消息了。