Structure for big GWT project

Question

Context

• big project with multi maven module or single maven module structure

Question

• did you finally use multi-maven-module or single-maven-module structure?

Details

If you've worked on a big project that had long development duration and contains lots of functionality(i.e. not a trivial project), did you choose to split the project into multiple maven modules or went with the single-module approach?

For example, having a multi-module structure, crashes when running maven commands like mvn gwt:eclipse(see http://bit.ly/gs4Rmo). I guess this would have worked well with single module GWT project. And there could be other commands like the above that has issues with multi-module structure.

However, the multi-module structure could bring the benefits of a faster development, i.e. if you separate the "server" from "client" module, you could compile the business logic(server) separately and package it into resulting web archive. Compiling the GWT code, takes about 20 seconds, so if you only modify the server package, it could save you lots of time in the long run.

Which other cases like the one above did you encounter when working with a multi-module/single module project?

Thank you!

Answer 1

A few notes:

1. On development server you don't have to compile the code "by hand": dev server compiles the code automatically and reloads it. Just keep dev server running, change some code and then reload the page in browser. (this is only true if you change existing classes and don't change project structure)

2. Multiple maven modules have nothing to do with multiple GWT modules.

3. You would want to have multiple GWT modules (= multiple entry points) if you have code that executes in different environments: for example you have web and mobile sites that have quite different code bases. Then you would split the project into three modules: web, mobile and common. Then you'd reference common in both web and mobile.

4. Another case for multiple GWT modules would be if you, for some reason, want to have a multiple host (entry) HTML pages. There are rare cases when you'd want this, for example when you need to do redirects when integrating OpenID. The other case would be that you already have existing Web pages where you are only adding GWT to add some functionality.

5. Don't split the GWT project into multiple modules just to reduce download size: use Code Splitting instead.

6. If your main gripe is long gwt compile times then read: How do I speed up the gwt compiler?

Answer 2

We started with multiple modules and eventually merged into a single module. The main reason for this was maintenance of modules is a huge overhead. Each module had a pom to build the UI, RPC layer and backend services. So with 30 modules we had 90 maven projects to manage.

Merging the modules turned 90 maven projects into 3 with one parent level pom.

This considerably lowers maintenance overhead and improves build times. GWT's compiler is notoriously slow so having a single compile parsing source files once instead of multiple times makes things much faster.

On the flip side, a single module means the compiler slurps everything up into memory at once. This could make split points intolerably slow to find if you insert any in your code. Therefore if you intend to split, it may be worth considering where you're putting those points and arrange your project accordingly.