gwt-serviceworker-linker

The ServiceWorkers specification enables applications to take advantage of persistent background processing, including hooks to enable bootstrapping of web applications while offline. This project attempts to basic AppCache behaviour using ServiceWorkers.

Quick Start

The simplest way to serviceworker enable a GWT application is to;

• add the following dependencies into the build system. i.e.

<dependency>
   <groupId>org.realityforge.gwt.serviceworker</groupId>
   <artifactId>gwt-serviceworker-linker</artifactId>
   <version>0.02</version>
   <scope>provided</scope>
</dependency>

• add the following snippet into the .gwt.xml file.

<module rename-to='myapp'>
  ...

  <inherits name="org.realityforge.gwt.serviceworker.Linker"/>

  <!-- enable the linker that generates the serviceworker javascript -->
  <add-linker name="serviceworker"/>

  <!-- configure all the static files not managed by the GWT compiler -->
  <extend-configuration-property name="serviceworker_static_files" value="./"/>
  <extend-configuration-property name="serviceworker_static_files" value="index.html"/>
</module>

• launch the service worker from within the application using Elemental2.

import static elemental2.dom.DomGlobal.*;

...

if ( null != navigator.serviceWorker )
{
  navigator.serviceWorker
    .register( GWT.getModuleName() + "-sw.js" )
    .then( registration -> {
      console.log( "ServiceWorker registration successful with scope: " + registration.getScope() );

      // Every minute attempt to update the serviceWorker. If it does update
      // then the "controllerchange" event will fire.
      DomGlobal.setInterval( v -> registration.update(), 60000 );

      return null;
    }, error -> {
      console.log( "ServiceWorker registration failed: ", error );
      return null;
    } );

  navigator.serviceWorker.addEventListener( "controllerchange", e -> {
    // This fires when the service worker controlling this page
    // changes, eg a new worker has skipped waiting and become
    // the new active worker.
    console.log( "ServiceWorker updated ", e );
  } );
}
  ...

This should be sufficient to get your application using a serviceworker to cache static assets.