Struts에서 데이터를 내보내고 CSV 형식으로 다운로드(HttpServletResponse)

기똥차!고구마는 앞에서 언급한 바와 같이 StreamResult 결과 형식은 HttpServletResponse 대상이 되돌아오는 Servlet OutputStream 대상을 이용하여 클라이언트에게 다운로드한 파일의 이진 데이터를 출력한다.(책'Struts 2 자세히 보기'에서 발췌)
 
streamResult를 사용하는 경우 프로그램 실행 프로세스에서 DoExecute 메서드를 호출합니다. 소스 코드는 다음과 같습니다.
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  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();
        }
    }

위 코드를 이해한 후에는 StreamResult 대신 HttpServletResponse를 사용하여 다음과 같은 CSV 파일 다운로드를 수행할 수 있습니다.
public String exportUserInfo() {
		StringBuffer strBuffer = new StringBuffer();
		while(it.hasNext()){
			User user = (User)it.next();
			strBuffer.append(user.getUserNo()+"
"); } 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; }
 
이렇게 하면streamresult를 사용하지 않아도 다운로드 기능을 실현할 수 있다.
PS: 위에서 되돌아오는 것은 반드시 NONE이어야 하며, SUCCESS라면;그러면 다음 오류가 발생합니다.
2011-1-24 10:30:07 org.apache.catalina.core.ApplicationDispatcher invoke
  : 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
  : 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)

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