Trouble in java.io.File.DeleteONExit()

Question

//at my servlet
String prjTmpPath= request.getRequestURL().toString();
prjTmpPath=prjTmpPath.substring(0,path.lastIndexOf("/"));
File tmpFile = File.createTempFile("000000book", ".pdf");
tmpFile.deleteOnExit();
-----------------copy temp file to prjTmpPath-----------------------------------
tmpFile.delete();
File prjTempFile=new File(tmpFile+"/"+tmpFile.getName());
//<------I only want to get the temporary file name for Multi users
prjTempFile.deleteOnExit();
-------------------do--PDF file create here-----------..............and open the created PDF file in the next jsp file.
but when i closed the browser and close the programme ,but the 000000book7109.pdf file is still existed in my project folder.
I think the temporary file will be deleted when the programme terminates or JVM terminates .and i try to close All.for delete it .
I was failed.
what can i do ?
thanks

Answer 1

A couple of things:
1. As a servlet programmer, you have no way of knowing when the JVM running the servlet container is going to close. It could be months before the container is rebooted.
2. DeletOnExit is not guaranteed to work (check the API docs)
3. The appropriate place to delete this file would be after it has been served. Create another servlet for downloading PDF files, then pass in the PDF document name as a parameter. Once the servlet returns the contents of the file to the http stream (there are tons of examples of how to do this type of thing, both in this newsgroup and Google), delete the file.
If deleting the file immediately is not to your liking (who knows, maybe the user needs to be able to click the refresh button), then you can tie the file to the user session and only delete it if the session is no longer valid (natch, you'll have to have a queue of files pending deletion, and run through it every now and then to clean it out).
If you are willing to give up some determinate behavior, I suppose you could delete the file in the finalize() method of a reference object in the session scope, but I'll probably get yelled at for even suggesting it, because there is not guarantee of when (or even if) the finalize() method will be called.
- K