Friday, December 01, 2006

Maven 1.x and Google Web Toolkit

I'm fiddling with Google's Web Toolkit with an eye to using it to produce a new front end to a web app I've written. I'm a big fan of Maven and wanted to get my head round setting up a GWT project which runs as a maven project (and thenceforth within my IDE of choice - Netbeans). There is a maven plugin (actually there is one for Maven 1 and another for Maven 2) for GWT but the docs are a little sparse. I had a fiddle and soon got things going but I had a few problems along the way. Here's what I had to do (assuming you already have Maven 1.0.x installed):
  1. Download and install the current version of GWT for your platform. Instructions and binaries are here. Put the install directory in your path.

  2. Obtain the GWT plugin. This example currently only works with the 1.0 version. You need to get it from here and then after unzipping it cd into the expanded folder and run the command: maven plugin:install-now

  3. Then you need to get the GWT jar files (and .dll's) into your Maven repository. You'll find them in your GWT install directory. I copied them to a new ./.maven/repository/ folder. I had to place gwt-dev-windows.jar, gwt-servlet.jar, gwt-user.jar, swt-win32-3235.dll and gwt-ll.dll in there to get this all to work fine. NOTE: You could get the jars automatically too but I was behind a firewall and too lazy to set up Maven to get through it.

  4. Now you can create your new GWT project. Create a directory (e.g. "./sample/") to house your project somewhere sensible, change directory into it and run the following command:applicationCreator com.mydemo.gwt.client.SimpleDemo.This will create you a source code directory ("./src/") containing a hello world-style GWT application and two scripts for compiling and running your app.

  5. Now we need to mavenise the directory structure. To do this change directory into ./src/ and create three new directories called java, webapp and test. Then move the auto generated com directory and it's contents into the new ./java/ folder. NOTE: We won't use the webapp directory this time, but it's where we would put things like the web.xml file if we had servlets as part of this application.

  6. Finally we need to create the required maven config files as follows which all live in the project root directory ("./sample/" in our case). NOTE: You'll need to edit the bits in red to suit your app and workstation:


<?xml version="1.0" encoding="UTF-8"?>
<name>GoogleWebToolkit and Maven Demo</name>
<!-- Unit test classes -->


<?xml version="1.0" encoding="UTF-8"?>
<project xmlns:j="jelly:core">
<preGoal name="war:war">
<attainGoal name="gwt:compile"/>

google.webtoolkit.home=C:\Program Files\GoogleWebToolkit\gwt-windows-1.2.22

That's it, you're ready to go. Just run the maven target "gwt" and you'll see your app in the google debugger.

NOTE: This borrows heavily from an introduction to the maven GWT plugin created by Rober Cooper. His article on O'Reilly can be found here and the google code project for the plugin is here.


Todd Huss said...

The problem I found with this approach is that making gwt:compile a pregoal of war:war results in war:webapp getting run twice (because it is a prereq for both gwt:compile and war:war) and that results in your unit tests getting run twice. As a hack I've prefixed the attainGoal with a j:set var maven.test.skip=true.

Andrew Law said...

Cheers Todd,

Great comment. I'll give it a try.