问题
I've got a communication between client and server. The process is simple:
- I'm making an AJAX POST request to a controller which generates a pdf in the file system
- On success of the above request a form GET request is made to get the pdf back and the standard browser "save or open" dialog box opens up
The reason I'm having a two step process is because I need to have a progress bar while the pdf is being generated.
The reason of the second request being a form submit rather than part of the AJAX request is because I can't get the standard browser "save or open" dialog box.
The problem with this approach is that IE7 & IE8 pop up a their annoying notification bar notifying the user that the it is dangerous to download the content and I don't want that.
So:
- I need the progress bar.
- If I go for an AJAX request only I need a way to pop up the "save or open" dialog box.
- If I go for the a form GET submit I need a way of knowing when the file has been generated in order to stop the progress bar, something like a shared flag between server and client.
Any help appreciated.
回答1:
One possible (a little of an anti pattern) workaround is this, but it's not a great design probably
However I've seen this (and admit I did this) before, and except some guilt, it did the trick
user clicks a link that goes to the servlet that generates the PDF and will just wait (timeout settings should be applied) until it's ready... (Content-Disposition header etc...) just like a regular download
The servlet will report progress on a shared session variable while generating the PDF
an AJAX call to the server will read from the session variable the progress and show to the user
when the PDF is done, the browser will just download it (request timeout risk perhaps)
The main issue here is using the request thread as a worker thread and blocking it, which may give this answer a couple of downvotes...
I'm not that familiar with Message Driven Beans but this is another, probably better solution.
来源：https://stackoverflow.com/questions/10536425/how-to-show-a-progress-bar-while-generating-a-pdf-file-for-download-without-ie