Struts导出数据并以CSV格式文件下载(HttpServletResponse)
给力吧！????? 红番薯
在前面一篇《Struts导出数据并以CSV格式文件下载(StreamResult)》中提到过：
StreamResult结果类型利用HttpServletResponse对象返回的ServletOutputStream对象向客户端输出下载文件的二进制数据。（摘自书籍《Struts 2深入详解
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如果使用streamResult，程序执行过程将调用其doExecute方法，源代码如下：
protected void doExecute(String finalLocation, ActionInvocation invocation) throws Exception { // Override any parameters using values on the stack resolveParamsFromStack(invocation.getStack(), invocation); OutputStream oOutput = null; try { if (inputStream == null) { // Find the inputstream from the invocation variable stack inputStream = (InputStream) invocation.getStack().findValue(conditionalParse(inputName, invocation)); } if (inputStream == null) { String msg = ("Can not find a java.io.InputStream with the name [" + inputName + "] in the invocation stack. " + "Check the <param name="inputName"> tag specified for this action."); LOG.error(msg); throw new IllegalArgumentException(msg); } // Find the Response in context HttpServletResponse oResponse = (HttpServletResponse) invocation.getInvocationContext().get(HTTP_RESPONSE); // Set the content type if (contentCharSet != null && ! contentCharSet.equals("")) { oResponse.setContentType(conditionalParse(contentType, invocation)+";charset="+contentCharSet); } else { oResponse.setContentType(conditionalParse(contentType, invocation)); } // Set the content length if (contentLength != null) { String _contentLength = conditionalParse(contentLength, invocation); int _contentLengthAsInt = -1; try { _contentLengthAsInt = Integer.parseInt(_contentLength); if (_contentLengthAsInt >= 0) { oResponse.setContentLength(_contentLengthAsInt); } } catch(NumberFormatException e) { LOG.warn("failed to recongnize "+_contentLength+" as a number, contentLength header will not be set", e); } } // Set the content-disposition if (contentDisposition != null) { oResponse.addHeader("Content-Disposition", conditionalParse(contentDisposition, invocation)); } // Set the cache control headers if neccessary if (!allowCaching) { oResponse.addHeader("Pragma", "no-cache"); oResponse.addHeader("Cache-Control", "no-cache"); } // Get the outputstream oOutput = oResponse.getOutputStream(); if (LOG.isDebugEnabled()) { LOG.debug("Streaming result [" + inputName + "] type=[" + contentType + "] length=[" + contentLength + "] content-disposition=[" + contentDisposition + "] charset=[" + contentCharSet + "]"); } // Copy input to output LOG.debug("Streaming to output buffer +++ START +++"); byte[] oBuff = new byte[bufferSize]; int iSize; while (-1 != (iSize = inputStream.read(oBuff))) { oOutput.write(oBuff, 0, iSize); } LOG.debug("Streaming to output buffer +++ END +++"); // Flush oOutput.flush(); } finally { if (inputStream != null) inputStream.close(); if (oOutput != null) oOutput.close(); } }?了解了上面的代码后，可以不使用StreamResult，而使用HttpServletResponse来实现CSV的文件下载，代码如下:
public String exportUserInfo() {StringBuffer strBuffer = new StringBuffer();while(it.hasNext()){User user = (User)it.next();strBuffer.append(user.getUserNo()+"\n");}HttpServletResponse response = ServletActionContext.getResponse();response.setHeader("Content-Disposition", "attachment;filename="+getGroup().getGroupName()+".csv");response.setContentType("APPLICATION/OCTET-STREAM");try {response.getOutputStream().print(strBuffer.toString());response.getOutputStream().flush();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}finally{try {response.getOutputStream().close();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}}return NONE;}?这样无需使用streamresult也可以实现下载功能。
PS:上面中返回必须是NONE,如果是SUCCESS;的话 就出现以下错误：
2011-1-24 10:30:07 org.apache.catalina.core.ApplicationDispatcher invoke严重: Servlet.service() for servlet jsp threw exceptionjava.lang.IllegalStateException: getOutputStream() has already been called for this responseat org.apache.catalina.connector.Response.getWriter(Response.java:610)at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:198)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.commons.exception_jsp._jspService(exception_jsp.java:72)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.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 org.apache.struts2.dispatcher.ServletDispatcherResult.doExecute(ServletDispatcherResult.java:161)at org.apache.struts2.dispatcher.StrutsResultSupport.execute(StrutsResultSupport.java:186)at com.opensymphony.xwork2.DefaultActionInvocation.executeResult(DefaultActionInvocation.java:373)at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:277)at org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:52)at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:485)at org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:395)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)at cn.gzjp.unimusic.cms.filter.HibernateThreadFilter.doFilter(HibernateThreadFilter.java:37)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)at cn.gzjp.unimusic.cms.filter.RequestRightFilter.doFilter(RequestRightFilter.java:74)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:852)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(Unknown Source)2011-1-24 10:30:07 org.apache.catalina.core.StandardWrapperValve invoke严重: Servlet.service() for servlet default threw exceptionjava.lang.IllegalStateExceptionat org.apache.catalina.connector.ResponseFacade.sendError(ResponseFacade.java:407)at org.apache.struts2.dispatcher.Dispatcher.sendError(Dispatcher.java:771)at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:506)at org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:395)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)at cn.gzjp.unimusic.cms.filter.HibernateThreadFilter.doFilter(HibernateThreadFilter.java:37)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)at cn.gzjp.unimusic.cms.filter.RequestRightFilter.doFilter(RequestRightFilter.java:74)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:852)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(Unknown Source)?