Introduction

The Maven Plugin for GWT aims at making it easier to build GWT projects with Maven, by providing specific goals, lifecycles, and artifact handlers.

Java code in GWT falls into two buckets:

• code that's shared between the client and server (RPC interfaces and DTOs, RequestFactory interfaces, and other shared code), and
• code that's entirely client-side. That bucket can be subdivided in two again:
  • library code, that needs to be packaged both in compiled and source form; and
  • application code, that will only be compiled to JavaScript through the GWT Compiler.

With Maven, shared code is just a standard project with jar packaging. You'd use the maven-source-plugin's jar-no-fork goal to package the sources as an attached artifact, then in your GWT project add dependencies on both the normal JAR and the sources JAR (with <classifier>sources</classifier>), and possibly add a GWT module (*.gwt.xml file) in the appropriate package, or a <source path="shared" /> in an existing GWT module, within the GWT project. Most of the time, such shared code is part of one multi-module project, so adding things in another module isn't really a code-smell. For more complex scenarios, you'd better create a client library (sometimes called an adapter library) that depends on the shared one and add the GWT-specific files (see below).

Client-only libraries bundle both the compiled classes and their sources, along with a GWT module and possibly other GWT-specific files (UiBinder, etc.) Libraries only depend on other client-only libraries, or on shared libraries and their sources. Some libraries also need to emulate classes from shared libraries, using GWT's super-source feature. Finally, unit-tests will need special treatment if they use GWTTestCase.

Last, but not least, applications are similar to client-only libraries, but their output is JavaScript, CSS, images, etc. after the Java sources and the resources have been processed by the GWT Compiler.

The Maven Plugin for GWT makes it easier to build the two kinds of client-only artifacts, and consume shared libraries.