Community contributed extensions

Play GWT2 Module Version 1.6

Play GWT2 1.6 provides some classes and commands to simplify the integration of a GWT 2.2.0 Module in a play application.

This module has been tested with play 1.2 and gwt 2.2.0

In the version 1.6
* Add GWT2SercieAsync annotation to define if a GWT2Service need to be invoked asyncron as aJob
* Add GWT2Chain concept to enable no async service to run Promise/Future/Job async with a callback With this you can start as many future as you want without blocking the service thread
* Add new Async Sample
* Improve errors handling
* some bug fixes

h2. Installation

1. This module does not includes GWT SDK. You will need to download it. ( version 2.0.0 )

2. Set GWT_PATH (or GWT_HOME) environment variable.

> export GWT_HOME=<path to gwt foder>

3. Create a new Play! application or use an existing one.

> play new myApp

4. Go to your application

> cd myApp

5. Edit /conf/dependencies.yml files, and add gwt2 module:

~# Application dependencies
~    - play
~    - play -> gwt2 1.6

6. Install GWT2 module.

> play install gwt2

TIPS: Skip the previous command if you want to install the module directly in the “modules” folder of your application.

p. 7. execute the next command to add the module to your play application

> play deps
h2. <a>Initialize you Application</a> 
bc. play gwt2:init

this will
- create a folder in your application : myApp/app/gwt (directory for gwt modules)
- create a folder in your application : myApp/gwt-public (directory for GWT compiled resources)
- and copy gwt-user.jar to myApp/lib
- Add a default App.gwt.xml in your myApp

if you want to change get path for you gwt modules, edit the conf/application.conf file and add theese lines

# GWT2 Configuration
# ~~~~~
# gwt2.modulesdir=<modulesdir> 
# it will be use to know where are gwt modules
# default: gwt
# gwt2.publicdir=<publicdir>
# it will be use to know where are the public directory for compiled module and for routing
# default: gwt-public
# gwt.publicpath=/<path>
# it will be use for routing configuration
# default: /app

then you can set you personal folder to use

if you want to manage the gwt-user.jar with play dependencies, add gwt-user to your play dependencies file.

~# Application dependencies
~    - play
~    - play -> gwt2 1.6
~    - -> gwt-user 2.2.0

Remove lib/gwt-user.jar

> rm lib/gwt-user.jar

then run “play deps” again

> play deps

Update your route file

Update your route file to add gwt2 dynamic routing

*		/      module:gwt2

Create a GWT Module create your module like this:

play gwt2:create myApp

this will ask you a gwt module name

What is the gwt module name ?

enter for eg: firstmodule

this action create some files

myApp/app/gwt/firstmodule/Firstmodule.gwt.xml (module)
myApp/app/gwt/firstmodule/public/index.html (default page for entry point)
myApp/app/gwt/firstmodule/client/ (entry point)

GreetingService Interface must use annotation @RemoteServiceRelativePath(“greeting”)

Service Implementation must implements GWTService, be place in the package, and named as define in annotation @RemoteServiceRelativePath

Or if you want to place your service or name it differently, eg:, you must use @GWT2ServicePath(“/firstmodule/greet”) annotation

Testing you GWT Module with dev mode

First start you Play application.

play run myApp

Then start the dev mode,

play gwt2:devmode myApp

GWT will compile your modules at first time.

Now you access your gwt module this url /app/firstmodule/index.html

Compiling a module

To compile a module (eg: before deployment)

play gwt2:compile myApp

this will ask you a gwt module name

What is the gwt module name ? 

Enter a name, then GWT will compile your module.

Remove a GWT Module

As for creating a new GWT Module but use gwt2:remove

play gwt2:remove myApp

this will ask you a gwt module name

What is the gwt module name ?

all directory of your module will be deleted:
- myApp/app/gwt/firstmodule/**
- myApp/gwt-public/firstmodule/**


You can use @GWT2ServiceAsync to invoke your GWT2 service normaly or as a play job


If you don’t use @GWT2ServiceAsync you can use GWT2Chain in your GWT2Service to run Promise/Future/Job normaly or async with callback

for that you will use GWT2Service.chain(Future, GWT2Chain) for synced call (blocking thread) or GWT2Service.chainAsyn(Future, GWT2Chain) for async call (non blocking thread)

See gwt2async sample.

Debugging the GWT UI

1. The easiest way it to eclipsify, netbeansify, ... you application and then use you prefered IDE to use JPDA. By default GWT listen on port 3408.

Creating a service using GWT-RPC

this part is the same as the Play-GWT by Rustem Suniev.

If you follow the GWT manual, it will explain you how to expose a service with GWT-RPC using a RemoteServiceServlet.

Exposing a GWT service with Play is almost the same, but since you can’t define servlets in a Play application, you have to use the provided support class, play.modules.gwt.GWTService

For example, to implement this service:

package gwt.mymod.client;
public interface HelloService extends RemoteService {
    String sayHello(String name);

simply create a class that extends the play.modules.gwt.GWTService, and define the service URL path with the play.modules.gwt.GWTServicePath annotation. Like this:

package services;
import play.modules.gwt2.GWT2Service;
import play.modules.gwt2.GWT2ServicePath;
import gwt.mymod.client.HelloService;
public class HelloServiceImpl extends GWT2Service implements HelloService {
    public String sayHello(String name) {
        return "Hello " + name;

This is the only difference from the GWT documentation.

Using Play Model You can use Play Model directly with your GWT Services. For that you have 2 solutions.

1. the first one is to create JPA Entity without extending play.db.jpa.Model

public class MyModel 
	@Column(name="text", nullable=false, length=100)
	public String someText;

You will have to use JPA.em().

2. the second one is to extends your model with play.db.jpa.Model and add a Custom Field Serializer side to the model class.
public class MyModel extends Model 
	@Column(name="text", nullable=false, length=100)
	public String someText;
public class MyModel_CustomFieldSerializer {
	public static MyModel instantiate(SerializationStreamReader reader)
		throws SerializationException {
		return new MyModel();
	public static void serialize(SerializationStreamWriter writer,
			MyModel instance)
		throws SerializationException {
	public static void deserialize(SerializationStreamReader reader,
			MyModel instance)
		throws SerializationException { = (Long) reader.readObject();
		instance.someText = reader.readString();


You will find 2 samples in the folder “samples” in the play gwt2 modules.

1. simple test
This sample is just a basic gwt module create with:
- gwt2:init
- gwt2:create
- gwt2:compile

2. myModel
This sample is an basic gwt module wich use Play Model.

3. gwt2async
This sample show how to use async call inside a GWT2service doing long task without blocking any thread

to test any sample
a. cd> go to the sample folder
b. run> play deps
c. run> play gwt:compileall
d. run> play run


This Module is maintained by Vincent Buzzano and was originaly based on the GWT Plugin by Rustem Suniev.