在我们做struts2文件下载的时候，经常会遇到这种问题：点“打开/保存”一切正常，但当我们点击“取消”时，却报一堆的异常，非常让人头疼，错误如下（每个人的错误估计不太一样，以我的为例）：
2011-5-19 10:30:23 org.apache.catalina.core.ApplicationDispatcher invoke
严重: Servlet.service() for servlet jsp threw exception
java.lang.IllegalStateException: getOutputStream() has already been called for this response
at org.apache.catalina.connector.Response.getWriter(Response.java:611)
at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:198)
at javax.servlet.ServletResponseWrapper.getWriter(ServletResponseWrapper.java:112)
at javax.servlet.ServletResponseWrapper.getWriter(ServletResponseWrapper.java:112)
at org.apache.jasper.runtime.JspWriterImpl.initOut(JspWriterImpl.java:125)
at org.apache.jasper.runtime.JspWriterImpl.flushBuffer(JspWriterImpl.java:118)
at org.apache.jasper.runtime.PageContextImpl.release(PageContextImpl.java:180)
at org.apache.jasper.runtime.JspFactoryImpl.internalReleasePageContext(JspFactoryImpl.java:118)
at org.apache.jasper.runtime.JspFactoryImpl.releasePageContext(JspFactoryImpl.java:77)
at org.apache.jsp.layout.adminlayout_jsp._jspService(adminlayout_jsp.java:204)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:377)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:389)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at com.opensymphony.module.sitemesh.filter.PageFilter.doFilter(PageFilter.java:39)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:646)
at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:551)
at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:488)
at com.opensymphony.module.sitemesh.filter.PageFilter.writeDecorator(PageFilter.java:173)
at com.opensymphony.module.sitemesh.filter.PageFilter.applyDecorator(PageFilter.java:158)
at com.opensymphony.module.sitemesh.filter.PageFilter.doFilter(PageFilter.java:62)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.struts2.dispatcher.ActionContextCleanUp.doFilter(ActionContextCleanUp.java:102)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.tuckey.web.filters.urlrewrite.RuleChain.handleRewrite(RuleChain.java:164)
at org.tuckey.web.filters.urlrewrite.RuleChain.doRules(RuleChain.java:141)
at org.tuckey.web.filters.urlrewrite.UrlRewriter.processRequest(UrlRewriter.java:90)
at org.tuckey.web.filters.urlrewrite.UrlRewriteFilter.doFilter(UrlRewriteFilter.java:417)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:857)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
at java.lang.Thread.run(Thread.java:619)
异常原因分析：
[stream对应的类是org.apache.struts2.dispatcher.StreamResult，该类的处理过程如下：
- 配置其中result标签下的各个参数
- 从服务器中获取输入流，并同时与客户端建立输出流（服务器与客户端链接通过Socket进行连接）
- 当点击“保存”或“打开”时，开始传输数据。如果点击“取消”，关闭所有的流
这里要注意的是，但是实际发现Socket并没有断开！并且流也没有关闭！这一点非常重要！
所以在JSP容器通过Response获取输出流之前，前面的流并没有关闭，所以会造成该异常的报出。
我在CSDN上搜了一个人的解决方法，他是这么解决的：
<package name="default" extends="json-default" namespace="/">
<!-- 定义全局Result -->
<global-results>
<result name="client-abort-exception">/null.jsp</result>
</global-results>
</package>
<package name="main" extends="default" namespace="/">
<action name="download" class="fileAction" method="download">
<exception-mapping result="client-abort-exception" exception="org.apache.catalina.connector.ClientAbortException"></exception-mapping>
<param name="savePath">/upload/download</param>
<!-- 文件下载配置结果类型为stream的结果 -->
<result name="download" type="stream">
<param name="inputName">targetFile</param>
<!-- 指定保存还是直接打开要下载的文件默认为：直接打开，这里配置保存 -->
<param name="contentDisposition">attachment;filename="${downloadFileName}"</param>
<!-- 指定下载文件的缓存大小 -->
<param name="bufferSize">4096</param>
</result>
</action>
</package>
也就是说，如果抛出了ClientAbortException异常，那就跳转到“null.jsp”这个页面，这个页面中什么内容都没有。虽然这种方法暂时可行，但是当遇到其他异常的时候，也就是非ClientAbortException之后，这个方法就不可行了。我之前也是参照这种方法配置，但昨天我重新启动应用的时候，点击“取消”居然还报错，错误就是上面的一堆“java.lang.IllegalStateException”，而且这种方法也是一种逃避的方法，也就是置之不理。这并不可取，解决问题就要解决彻底明了，逃避是没用的，经过网上大师们的分析测试，最终解决办法如下：
- 下载一个插件struts2-sunspoter-stream-1.0.jar（附件中有下载）
- 将附件解压获取struts2-sunspoter-stream-1.0.jar，并复制在/WEB-INF/lib下
- 在原有的struts.xml的基础上进行相应的配置，配置如下：
<package name="main" extends="default" namespace="/">
<!-- 添加如下内容 -->
<result-types>
<result-type name="streamx" class="com.sunspoter.lib.web.struts2.dispatcher.StreamResultX"/>
</result-types>
<action name="download" class="fileAction" method="download">
<param name="savePath">/upload/download</param>
<!-- 文件下载配置结果类型为streamx -->
<result name="download" type="streamx">
<param name="inputName">targetFile</param>
<!-- 指定保存还是直接打开要下载的文件默认为：直接打开，这里配置保存 -->
<param name="contentDisposition">attachment;filename="${downloadFileName}"</param>
<!-- 指定下载文件的缓存大小 -->
<param name="bufferSize">4096</param>
</result>
</action>
</package>
在这种方式下，只需添加一个result-type，将原有的result中type改为“streamx”，其他一律不变，在这种情况下，点击“取消”的同时也关闭了流，不会再报出该异常。
如果出现log4j的警告，比如：
21:23:44,676 WARN StreamResult:45 - StreamResultX Warn : socket write error
出现该警告说明正确执行，该警告说明，Socket非正常中断，但是流确实已经关闭，自此再也不用看到上面出现的讨厌异常结果。
网友评论