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 》）

 

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 block
			e.printStackTrace();
		}finally{
			try {
				response.getOutputStream().close();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.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 exception
java.lang.IllegalStateException: getOutputStream() has already been called for this response
	at 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 exception
java.lang.IllegalStateException
	at 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)