(Quick Reference)

6 Static Resources

Version: 6.0.0

6 Static Resources

Grails 3 integrates with the Asset Pipeline plugin to provide sophisticated static asset management. This plugin is installed by default in new Grails applications.

The basic way to include a link to a static asset in your application is to use the resource tag. This simple approach creates a URI pointing to the file.

However modern applications with dependencies on multiple JavaScript and CSS libraries and frameworks (as well as dependencies on multiple Grails plugins) require something more powerful.

The issues that the Asset-Pipeline plugin tackles are:

  • Reduced Dependence - The plugin has compression, minification, and cache-digests built in.

  • Easy Debugging - Makes for easy debugging by keeping files separate in development mode.

  • Asset Bundling using require directives.

  • Web application performance tuning is difficult.

  • The need for a standard way to expose static assets in plugins and applications.

  • The need for extensible processing to make languages like LESS or Coffee first class citizens.

The asset-pipeline allows you to define your javascript or css requirements right at the top of the file and they get compiled on War creation.

Take a look at the documentation for the asset-pipeline to get started.

If you do not want to use the Asset-Pipeline plugin, you can serve the static assets from directories src/main/resources/public or src/main/webapp, but the latter one only gets included in WAR packaging but not in JAR packaging.

For example, if you had a file stored at /src/main/resources/public/images/example.png and your Grails application was running on port 8080, then you could access the file by navigating to http://localhost:8080/static/images/example.jpg.

Cache Configuration for Static Resources

By default, files under src/main/resources/public or src/main/webapp are served with an HTTP response header of Cache-Control: no-store. To have them be cached by the browser, you can set the configuration setting grails.resources.cachePeriod: number in application.yml so that they are served with a response header of Cache-Control: max-age=number indicating to the browser how many seconds the file should be considered fresh.