How to handle caching of GWT theme CSS files

Question

I've got an app written with Struts/Tiles/JSP that I'm adding a GWT app to. The non-GWT portion of my app handles css caching by actually writing out the css file with a version number taken from my svn repository attached, like this "styles.css?svnbuild=12345". That way I can tell the browser to cache those css files forever and when I deploy a new version all my users download it immediately.

Now I'm moving on to the GWT app and I love how it uses "longmd5sum.cache.css" as the filename so I can still tell the browser to cache it forever. The problem is that the css files associated with my theme, like "gwt-standard.css", don't have a strong name and don't have my svnbuild parameter attached. Whenever I deploy a new version of my app, users are still seeing the old version of the css which makes it look wrong.

Has anyone figured out a best practice for handling caching of gwt theme css files? Is there a way I can append an svnbuild parameter or something similar when appending the css to the document?

Answer 1

Ok. So after I posted this I dug into the GWT source code and found some links about creating a GWT custom linker.

http://development.lombardi.com/?p=29

http://code.google.com/webtoolkit/doc/1.6/DevGuideOrganizingProjects.html

Here's how I solved it with my own linker. First I made a linker class that extends the standard IFrameLinker:

@LinkerOrder(LinkerOrder.Order.PRIMARY)
public class MyLinker extends IFrameLinker {
    protected String generateStylesheetInjector(String stylesheetUrl) {
        stylesheetUrl = stylesheetUrl + "?buildtime=" + System.currentTimeMillis();
        return super.generateStylesheetInjector(stylesheetUrl);
    }
}

After that it's just a matter of telling your module to use your custom linker. In your module.gwt.xml file:

<module>
    <define-linker name="mylinker" class="com.company.gwt.core.linker.MyLinker" />
    <add-linker name="mylinker" />
</module>

Just tried it out and now in my nocache.js file it outputs a new timestamp every time I compile. My users can cache the css file forever and they will download a new one automatically whenever I deploy a new version of the app.