Disable Caching completely

General
1

Hi guys,

My question is short (and hopefully simple to solve!): How can I completely disable browser-caching in my webservice realized with vaadin?

I want to completely disable caching since I’m getting problems when I try to do some PDF streaming and displaying them in my browers.

I have read about a solution for my problem for example here:

http://stackoverflow.com/questions/1341089/using-meta-tags-to-turn-off-caching-in-all-browsers

They talk about adding some headers to the web application that disable browser caching. But how do I add them to my application?

A short code snippet would be very welcome (and helpful!) (to be honest: Answers in general would be great as well :smiley: )

Thanks once again for your help guys :slight_smile:

2

I think I solved my problem using an own servlet and the following code:


Can anyone confirm that what I’ve done is correct?

(the meta tags are from this post http://stackoverflow.com/questions/1341089/using-meta-tags-to-turn-off-caching-in-all-browsers )

	/**
	 * This prevents caching in all browsers, which would, if allowed, cause
	 * caching problems while streaming and displaying pdfs
	 */
	@Override
	protected void writeAjaxPageHtmlHeader(final BufferedWriter page,
			String title, String themeUri, HttpServletRequest request)
			throws IOException {
		super.writeAjaxPageHtmlHeader(page, title, themeUri, request);
		page.write("<meta http-equiv=\"cache-control\" content=\"max-age=0\" />");
		page.write("<meta http-equiv=\"cache-control\" content=\"no-cache\" />");
		page.write("<meta http-equiv=\"expires\" content=\"0\" />");
		page.write("<meta http-equiv=\"expires\" content=\"Tue, 01 Jan 1980 1:00:00 GMT\" />");
		page.write("<meta http-equiv=\"pragma\" content=\"no-cache\" />");
	}

Thanks a lot

3

Okay this didn’t work. I checked it with “about.cache” and it still caches happily on my webservice?
Can anyone here help me?

4

Hi,

See my response on
StackOverflow

What you’ve done above is to simply remove caching from the initial bootstrap page. Every subsequent request is handled in other methods within AbstractApplicationServlet - which are tricky to override, as some of them are private.

If you’re dealing with Vaadin streaming, add the parameters to the DownloadStream - otherwise, a servlet filter is probably your best bet. Details on SO.

HTH,

Cheers,

Charles.

5


Thanks for your answer here, as well as the more detailed one on stackoverflow.

More in Detail, I’m using a Streamresource (This code basically comes from another user vaadin example who has shown how to integrate a pdf into a vaadin window):

final Embedded pdfContents = new Embedded();
pdfContents.setWidth("500px");
pdfContents.setHeight("500px");
pdfContents.setType(Embedded.TYPE_BROWSER);

StreamResource resource = new StreamResource(new PDF(doc), randomString.generateRandomString(), WebsiteFrame.getDefault().getMainWindow().getApplication());
resource.setCacheTime(1000); 
// Set the right mime type
resource.setMIMEType("application/pdf");
pdfContents.setSource(resource);

Before I had the cache time set on “0”, I’ve changed it now to “1000” as marked in your post.

I also tried the setParameter()-Method you’re mentioning on SO, but it doesn’t exist for a StreamResource.

Still, I think I might have solved the issue through generating a random String as title for the pdf. I read somewhere in the vaadin forums that these forces the browser to always reload the pdf and not using the cached version. As far as I have tested this, I’m not experiencing any wrong pdfs displayed through the cache (While about:cache always showed me that the cache grew while a pdf is being displayed, which indicates a new pdf has been added under a new title)

So, basically, this could mean that the new random name did the trick, or what do you think?