getOutputStream() has already been called for this response

I'm currently developing a web application using struts 1.3.5 with tiles deployed on XP under tomcat 5.5

I've implemented a download facility to enable users to download
files by clicking on appropriate links. This has been achieved
using the struts file download action mentioned at

StrutsFileDownloadAction

The application works fine, and i can download a number of different
formats including pdf, zip etc.

However Problems arise when I perform stress testing using JMeter.

The following exception is thrown

"java.lang.IllegalStateException: getOutputStream() has already been called for this response"

I have the following settings for Jmeter.

Number of Threads: 1

Ramp-up Period : 1

Loop count : 50

I'd appreciate it if anyone could enlighten me as to what is actually going on.

The code is as follows

public class ExampleFileDownload extends DownloadAction 
{
private static final Log log = LogFactory.getLog(ExampleFileDownload.class);
 
protected String contentType = null;

@Override
/**
 * Override the super class getStreamInfo method
 * 
 */
protected StreamInfo getStreamInfo(ActionMapping mapping, 
   ActionForm form, 
   HttpServletRequest request, 
   HttpServletResponse response) throws Exception 
{

//Retrieve request parameter storing url to resource
String path = (String)request.getParameter("url");

//transform logical -> absolute path
Constants c = new Constants();

String absolute_path = c.transformLogicalToAbsolutePath(path);

//set content type
this.setContentType(absolute_path);

File file = new File(absolute_path);

response.setHeader("Content-disposition", "inline; filename="+file.getName());
 
//attempt to solve security-constraint problem which prevents
//opening download files due to IE bug reported since IE4.0 but
//still existing in IE6. See support.microsoft.com for article 821935:
//"Internet Explorer Cannot Download" error message when you use an https
//url to open an office document or pdf file.

response.setHeader("Pragma", "public");
response.setHeader("Cache-Control", "max-age=0");

return new FileStreamInfo(contentType, file);

}

A partial stack trace is given below

2007/7/04 17:07 40 [ERROR] org.apache.catalina.core.ApplicationDispatcher.invoke:L - 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:599)
at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:195)
at javax.servlet.ServletResponseWrapper.getWriter(ServletResponseWrapper.java:111)
at javax.servlet.ServletResponseWrapper.getWriter(ServletResponseWrapper.java:111)
at javax.servlet.ServletResponseWrapper.getWriter(ServletResponseWrapper.java:111)
at javax.servlet.ServletResponseWrapper.getWriter(ServletResponseWrapper.java:111)
at javax.servlet.ServletResponseWrapper.getWriter(ServletResponseWrapper.java:111)
at javax.servlet.ServletResponseWrapper.getWriter(ServletResponseWrapper.java:111)
...............................................................
...............................................................
...............................................................
at javax.servlet.ServletResponseWrapper.getWriter(ServletResponseWrapper.java:111)
at javax.servlet.ServletResponseWrapper.getWriter(ServletResponseWrapper.java:111)
at org.apache.jasper.runtime.JspWriterImpl.initOut(JspWriterImpl.java:124)
at org.apache.jasper.runtime.JspWriterImpl.flushBuffer(JspWriterImpl.java:117)
at org.apache.jasper.runtime.PageContextImpl.release(PageContextImpl.java:174)
at org.apache.jasper.runtime.JspFactoryImpl.internalReleasePageContext(JspFactoryImpl.java:115)
at org.apache.jasper.runtime.JspFactoryImpl.releasePageContext(JspFactoryImpl.java:75)
at org.apache.jsp.WEB_002dINF.common.Layout_jsp._jspService(Layout_jsp.java:85)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
...............................................................
...............................................................
...............................................................

kind regards,

Mo

I've seen situations where this exception is thrown because the download is being done within a tiles template. One way to avoid this would be to make sure a separate window is opened when the file downloads. You can do this by specifying target="_blank" in yor form tag.

Merrill

Thanks for the swift reply.

've seen situations where this exception is thrown because the download is being done within a tiles template. One way to avoid this would be to make sure a separate window is opened when the file downloads. You can do this by specifying target="_blank" in yor form tag.

I tried this but unfortunately I'm still getting the same error.
I'd appreciate any other suggestions you may have.

kind regards,
Mo

Originally posted by mo sayed:
Merrill

Thanks for the swift reply.

I tried this but unfortunately I'm still getting the same error.
I'd appreciate any other suggestions you may have.

kind regards,
Mo

Are you using two System.out & creating an OutputStream in your code?

I have seen this as the problem in other forums.