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)