ninja-core/src/main/java/ninja/AssetsController.java
private URL getStaticFileFromMetaInfResourcesDir(String fileName) {
        String finalNameWithoutLeadingSlash 
                = assetsControllerHelper.normalizePathWithoutLeadingSlash(fileName, true);
        URL url = null; 
        url = this.getClass().getClassLoader().getResource("META-INF/resources/webjars/" + finalNameWithoutLeadingSlash);
        return url;
    }
private URL getStaticFileFromMetaInfResourcesDir(String fileName) {
        String finalNameWithoutLeadingSlash 
                = assetsControllerHelper.normalizePathWithoutLeadingSlash(fileName, true);
        URL url = null; 
        url = this.getClass().getClassLoader().getResource("META-INF/resources/webjars/" + finalNameWithoutLeadingSlash);
        return url;
    }
Loads files from META-INF/resources directory.
This is compatible with Servlet 3.0 specification and allows
to use e.g. webjars project.