HTML5 manifest mime type in grails 5

I ran into an issue serving the proper mime type for a cache manifest from grails today, adding a ‘manifest’ key to grails.mime.types failed to register for some reason (if you know why, do tell!). Running on a server this can be addressed by setting the mime type directly in tomcat, but i needed to test locally using the built in Tomcat server. Hopefully this inability to serve a manifest mime type will be addressed soon, but in the meantime the workaround was to make the manifest a generated gsp and add the content-type declaration directly to the manifest:


<%@ page contentType="text/cache-manifest" %>CACHE MANIFEST
# rev 0
file.html


It’s important to keep CACHE MANIFEST on the same line as the contentType property – manifests are discarded if they don’t start from the first character with that declaration.

One last thing – this works better cross browser (where some browsers dont respect a manifest not ending in .manifest) by setting grails.mime.file.extensions to false, which will allow your mapping to be directly to cache.manifest, returning the rendered gsp.