Good point Jens. Here's some handy code that works well for me:
In the HttpServlet that servers up the index.html file:
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse
response) throws IOException {
String serverVersion = [LOAD YOUR SERVER VERSION]
String quotedETag = "\"" + serverVersion + "\"";
response.setHeader("ETag", quotedETag);
response.setHeader("Cache-Control", "no-cache, must-revalidate");
String ifNoneMatch = request.getHeader("If-None-Match");
// The browser has the latest version
if (quotedETag.equals(ifNoneMatch)) {
response.setStatus(HttpServletResponse.SC_NOT_MODIFIED); // 304 Not
Modified
}
// The browser needs the latest version
else {
String html = [LOAD YOUR HTML]
response.setContentType("text/html");
response.setCharacterEncoding("UTF-8");
response.getWriter().append(html);
}
}
You need a serverVersion somehow. If using Google App Engine, you can do
System.getenv("GAE_VERSION"); otherwise, it's up to you how you get it and
make it unique for each deploy.
On Friday, 13 February 2026 at 8:52:48 pm UTC+11 Jens wrote:
> Yeah, using the gwt property is the easiest solution. I also use it. But
> be aware that you now have to update your webserver configuration to tell
> the browser to not cache the index.html anymore. Otherwise the embedded GWT
> code will be outdated if you deploy an updated version of your GWT app and
> all the hashes of *.cache.js files have changed.
>
>
> -- J.
>
> Craig Mitchell schrieb am Freitag, 13. Februar 2026 um 02:00:28 UTC+1:
>
>> Thanks Colin. Dug around a little and figured out all I needed was:
>>
>> <meta name="gwt:property" content="baseUrl=/dt/" />
>>
>> ("dt" is my GWT module short name)
>>
>> Now everything works, including superdevmode. Ie: No need for the
>> gwtNoCacheJs.contains("superdevmode") check anymore.
>>
>> I think my page does load a bit faster now (on subsequent times, not the
>> first visit). https://drift.team/ if anyone is curious what the end
>> result root html source looks like.
>>
>> On Friday, 13 February 2026 at 10:16:23 am UTC+11 Colin Alworth wrote:
>>
>>> I believe that
>>> https://github.com/gwtproject/gwt/blob/main/dev/core/src/com/google/gwt/core/ext/linker/impl/computeScriptBase.js
>>>
>>> is what you're going to want to read, or possibly replace on your
>>> classpath. Alternatively, subclass the CrossSiteIframeLinker to override
>>> getJsComputeScriptBase(LinkerContext) to provide your own file.
>>>
>>> From that file:
>>> /**
>>> * Determine our own script's URL by trying various things
>>> *
>>> * First - use the baseUrl meta tag if it exists
>>> * Second - look for a script tag with the src set to
>>> MODULE_NAME.nocache.js and
>>> * if it's found, use it to determine the baseUrl
>>> * Third - if the page is not already loaded, try to use some
>>> document.write
>>> * magic to install a temporary tag and use that to determine the
>>> baseUrl.
>>> *
>>> * This is included into the selection scripts
>>> * wherever COMPUTE_SCRIPT_BASE appears with underlines
>>> * on each side.
>>> */
>>>
>>> The "Second" step is where you appear to be getting stuck - since there
>>> is no script tag with a src attr, the rest of the loading code doesn't know
>>> what to do. So, add a meta tag for baseUrl so the script knows where the
>>> other resources are loaded from.
>>>
>>> Note that I haven't messed with this in years, and might have missed a
>>> point or two.
>>>
>>> On Thursday, February 12, 2026 at 4:54:23 PM UTC-6
>>> [email protected] wrote:
>>>
>>>> I tried to inject the non-dev nocache.js into my main index.html file.
>>>> Like this:
>>>>
>>>> String gwtNoCacheJs = loadFileFromServlet("/dt/dt.nocache.js");
>>>>
>>>> if (gwtNoCacheJs.contains("superdevmode")) {
>>>> gwtNoCacheJs = "<script type='text/javascript'
>>>> src='/dt/dt.nocache.js'></script>";
>>>> }
>>>> else {
>>>> gwtNoCacheJs = "<script type='text/javascript'>\n" + gwtNoCacheJs + "
>>>> \n</script>";
>>>> }
>>>>
>>>> String html = loadFile("index.html").replace("XXX", gwtNoCacheJs);
>>>>
>>>> However, it doesn't work, as nocache.js wants to load files from the
>>>> same sub directory it's located in, and not the root directory.
>>>>
>>>> Has anyone done this? It probably isn't work the effort, as it'll only
>>>> save one network call, but I was curious if it's possible.
>>>>
>>>
--
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