Angular integration for GWT
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Write AngularJS Controllers, Filters, Directives in GWT

What? (is it)

This is a library that enables Authors to write components or complete apps for AngularJS in Java. This is mostly done using compiler castings for Google Web Toolkit to "compile" Java Code into Javascript.

Why? (GWT to write Angular modules)

AngularJS provides a MVVM framework for web apps, offering modularisation, IOC and allows to create reusable components while still allowing to create apps quickly. As every contemporary web app, AngularJS is built on Javascript.

GWT offers a way to write, test and distibute code in Java and compile it to Javascript. This library offers the possiblity to use GWT to create modules and apps for AngularJS using GWT.

Javascript is a very flexible and widespread language, however for mature languages like Java, a richer set of tooling regarding development, testing, versioning and distribution support is availiable. Also a large base of developers and libraries are availiable that can be migrated more easily.

How? (to use)

Best way to start is to take a look at the archetypes.


There are two archetypes:

  • angulargwt-module-archetype for a module project, where the GWT code is used by a AngularJS app in javascript
  • angulargwt-app-archetype for an app project, where the top-level-module is written in GWT

As usual mvn archetype:generate or an IDE such as m2e or NetBeans can be used for the archetypes.

Other ways to set up AngularGWT projects


You can build AngularGWT libraries or apps is using a maven plugin, such as the codehaus gwt-maven-plugin or the gwt-maven-plugin from Thomas Broyer

Integrate the following dependency into your pom.xml (adjust version number accordingly). It is on sonatype oss and releases are mirrored into maven central.


Current SNAPSHOT state: Build Status

manually add the lib to your project




Inheriting the GWT module

This inherits declaration is needed in your <yourmodule>.gwt.xml (note the namespace)

<inherits name="" />

Creating an AngularJS module

Every project you write will provide at least one AngularJS Module. Just extend AngularModule and provide the module name and the dependencies with the @NgName and the @NgDepends annotations. Also put all provided components (controllers, directives, services etc.) into the @NgDepends.

For example:

@NgDepends({MyService.class, MyFilter.class, MyController.class, MyDirective.class})
public class MyModule implements AngularModule {

Choosing a module or an application as project type

There are three ways a project is used:

  1. As Java library in another AngularGWT project
  2. As javascript containing AngularGWT modules used by an AngularJS app
  3. As javascript containing AngularGWT modules incl. the top-module

For compillation to javascript, a GWT entry point is needed.

App project

If you write not only a library module but an application (use case 3), you need to provide a entry-point class by extending AngularApp. You need to override the abstract method main(), which should return all referenced AngularGWT modules as an array.

public class MyApp extends AngularApp {
   protected AngularModule[] main() {
     return new AngularModule[] {(AngularModule) GWT.create(MyModule.class)};

The template(s) are then provided in the same way as usual for AngularJS and need to include the GWT-generated script. You do not need to include angularjs in the head, it will be lazy-loaded from the CDN if it is not detected.

A library of AngularGWT modules

For all other projects (use cases 1 or 2), you write a module and extend an entry-point in the same way from AngularEntryPoint

public class MyLib extends AngularEntryPoint {
   protected AngularModule[] main() {
     return new AngularModule[] {(AngularModule) GWT.create(MyModule.class)};

If you use this lib in Java (use case 1), you just add the classes and sources to the classpath (or let Maven do it).

If you use the compiled library as javascript in a regular AngularJS app (use case 2) then you have to delay the bootstrapping until the async loading of GWT has finished, this is done via a callback called angularGwtModuleLoaded.

The script angulargwt.js provides a very basic handler for this purpose.

So your AngularJS-app must not use <body ng-app="MyApp">, but instead include this:

<script type="text/javascript" src="angulargwt.js"></script>
<script type="text/javascript">	
		// This must be called instead of ng-app!

Refer to bootstrap process documentation of AngularJS for background.

Implementing the different types of AngularJS components

Refer to AngularJS concepts for a basic intro of the different types of components


A model is defined by its interface, which must extend from Model<> and use the own type as type parameter for the superinterface.

The Model is generated during compilation and in code it is invoked via deferred binding, which means you instatiate a Model via GWT.create().

public interface Person extends Model<Person> {
   String getName();
   Person setName(String name);
   int age();
   Person age(int age); 


Similar to the Model, a Scope is defined by contract (by its interface) and generated in the compilation process. Note that getters and setters can be implicit or explicit and use "fluent" or "void-setter" style.

public interface MyScope extends Scope<MyScope> {
   void setPersons(ArrayOf<Person> persons);
   ArrayOf<Person> getPersons();
   int maxPersons();
   MyScope maxPersons(int max);


Controllers extend the class ÀngularController<> and refer to their scope as type argument. The name to be used in the template is specified via @NgInject(name="ControllerName").

Each controller must implement the abstract function initialize(Scope scope), in which it initializes the scope.

To specify a component to be injected, it must be declared as a public field and annotated with @NgInjected

Watches are defined by annotating a Method with the @Watch annotation. The first parameter is the expression to be watched, the second parameter is a boolean that enforces deep object equality. The Method will be called when the watch expression changes with new and old value as parameters. Refer to Angular's documentation on $watch for background information.

@NgInject(name = "MyCtrl")
public class MyController extends AngularController<MyScope> {
    public MyService service;
    public void initialize(MyScope scope) {...}

    @NgWatch(value = "persons", objEq = true)
    public void $watchPersons() {...}
    public void $watchPath(String path) {...}
    //arbitrary functions to be called from the template
    public void clearPersons() {...}


A Filter is implementing the Filter interface with a type parameter for the Model it is filtering. It is injectable by annotating the class with @NgInject(name="filterName").

@NgInject(name = "todoFilter")
public class TodoFilter implements Filter<Todo> {
        public ArrayOf<Todo> filter(ArrayOf<Todo> todos, Todo todoFilterArg) {
            ArrayOf<Todo> result = JsArrayOf.create();
            //Filtering, e.g. by compairing with the Argument
            return result;


A service can provide Util methods and is just implemented as POJO and annotated with the name used for injection into the controllers.

@NgInject(name = "serverProxy")
public class ServerProxy {
    public ArrayOf<Todo> get() {...}
    public void put(ArrayOf<Todo> todos) {...}


Directives are defined as classes that implement the interface Directive. The class must also be annotated as @NgDirective("name").

Other components can be injected similar to the controller.

public class MyDirective implements Directive {

    public void init() {}

    public void link(final MyScope scope, final ArrayOf<NgElement> element, final JsonObject attrs) {

Supporting the project / to be done

  • More JavaDoc
  • Unit tests.
  • Transitive dependencies, modules that depend on modules.
  • JSO wrappers for the rest of the AngularJs API. (so far only what was needed for TodoMVC is implemented)


Since GWT is using Apache Licence and AngularJS is using MIT Licence, the usage of this code code should conform this both licences. I am happy for any legal advice on the proper licencing.


I forked this code from nordligulv, which is a fork from cromwellian, I merely buffed things up a bit and added this doc.

Written with StackEdit.