Spring ROO 1.2 review

This post as the title mentions, is about my personal impressions and thoughts about the 
'Spring ROO' framework, version 1.2.1.

What is ROO?
ROO is a tool, which helps automating the development process of web-applications written in Java.
It supports different kinds of technology stack, such as GWT & Spring MVC in the front end, JPA & Hibernate, EclipseLink in the back-end and such.
The framework is entirely based on the Spring framework, in order to accomplish the goal of creating a full-blown, end-to-end web-application.
The idea is to be able to rapidly create and maintain a web-application with a few 'shell' commands, and then let the users (the developers) fill in the gaps and customize business logic, application state and so on.

ROO monitors the changes the developer makes while writing code, and adapts the application's infrastructure to match and support the developer's actions.

I recommend you visit the ROO website in any case to get the best understanding of the tool.

Before I start telling you what I did and experienced I have to say that I enjoyed working with ROO.
The installation was fast & easy, the ROO shell was easy to use and the documentation was satisfying.

So! after some short-long intro, let me tell you -

What did I do?

1. Created a simple web-application based on a multi-module project - Server & Client modules.
2. Used GWT as the front-end, JPA over Hibernate with a DB in the back-end.
3. Wrote custom code and integrated it in the auto generated files of ROO.
4. Tried to change/add/remove a service (BL) & repository (DAO).
5. Inspected generated code.
6. Tried to remove project's dependency from ROO.

What I experienced
 1. The amount of code generated for the client module (GWT) was quite overwhelming. So many files were created to show/edit/create/delete a single entity named Product in the DB. While some of the generated code is absolutely necessary, a lot of code was created to support every possible option on the front-end.

Unfortunately, this is not configurable, and I could not find a way to tell ROO exactly what I wish to generate ('scaffold'), like - "only desktop support", "only mobile support", "only view/read" capabilities, etc... You can only pick which Entities on your model to scaffold (support on the front-end and back-end). All this leads to a very big codebase, which won't necessarily be used.
This leads to verbosity and a lot of redundancy, which makes your codebase larger and
more complex for no reason.

2. Front end's design - Is following Google's best practices which is really great. You can learn
quite a bit of Google's understanding the design of a web-application on the front end.

3. Generated code looks fairly neat, however all generated code managed by ROO is "hidden" in AspectJ files. - Some people don't like this.

4. No easy removal* of ROO from the project in my opinion... - You could just stop ROO from monitoring your application and continue developing your project. But, all the generated AspectJ files remain. This could be a problem for the future, in case you want to change your classes' implementation. (* - Please see comments at the bottom).

5. Writing tests & integrating them with Services layer was easy.

6. Great end-to-end integration tests, that run on the Browser using Selenium (some kind of a web-driver script player).

It feels to me that even though ROO's GWT add-on tried very hard to give a real added value to developers, it added more complexity than simplicity, and that is in my opinion due to the fact that 
a lot of code is being generated. And that makes it hard in the beginning to dive into the code.

Not to mention how much tweaking needs to be done to disable features for instance.

And in case you're letting ROO manage your project further, you will have to keep track of that
stuff all the time. So if you 'messed' up by scaffolding some entity which you didn't want, you'll spend
your time removing the unwanted code. where is the Undo feature of the shell?

ROO just doesn't feel as fine grained as I would expect it to be.

Conclusion
I think that ROO is walking in the right direction, empowering developers to deal only with the logic of their web applications and not trouble themselves with infrastructure and design problems of standard web-applications.
I am not sure I would use it (especially not the front-end) in production, yet.

Despite all that, it still benefits as a really nice tool for prototyping (or quickly setting up a back-end & DB configuration), and for learning how to implement a web app with best practices.

What can you profit from it:

1. It is an amazing tool to create a web-app POC very fast!
2. It is an awesome tool to learn new technologies and see how they work with each other.
3. Spring ROO applies best practices.
Explanation: ROO has a 'plug-ins' platform, which lets anyone to generate code following a simple command in the shell. 

Google for instance wrote such a plug-in for ROO to integrate with GWT. As a result you get the BEST, latest results for architectural/design/technology/practices on your web-app.

4. It's a great tool to get your backend Spring based infrastructure ready with a DB, in a few minutes, or see how it should be done properly.
5. Runtime performance - Best runtime performance you could have achieved yourself probably.
All generated code/configuration is processed in compile time as regular Java files only!
Following best practices of Spring & other vendors like Google, you can rest assure that there should be no performance issues caused by this tool. (or with very little chance for it to happen - even the best software giants have bugs sometimes).
6. Did I mention the great integration tests running automatically on the browser?
I personally loved this feature!

I think it would be wise to keep an eye on ROO for the future, as it has already been out there for some time, and keeps on improving.

Visit 'Spring ROO': http://www.springsource.org/spring-roo

DI with Guice for Java Swing

If you're familiar with Dependency Injection (DI) concepts and frameworks such as Spring,
you know the great benefits it introduces when developing an application.
Spring which I daily use (and praise), is a framework (or an application platform if to be more accurate) that one of its core features and philosophy is DI.

Some of the benefits of DI are well known:

1. Simplified code.
2. Reduced dependencies.
3. Helps 'modularity' and creation of reusable components.
4. Helps you test your application better.
5. Lazy loading.

Surely there are other benefits you could think of which were not mentioned above.
So, why not bring all that good stuff to your Rich Client ?

The connection of DI to the title of this post is how to integrate DI in your front-end in case you are building a Rich client application, using Java Swing or GWT for example.

You could follow the MVC pattern (which is well known, and can be great) to build your rich client, and integrate it with a DI framework. However I strongly recommend you consider the MVP pattern for an even better design of your front-end. Which I find it to be much 'cleaner'.
(In MVC some of the business-logic code is scattered between the controller and the View. It's harder
to re-use your View objects/Widgets, especially in case you want to give it to someone else to use, or integrate them in another product).

Smarter people than me talk about it, and you can find great talks on YouTube regarding this subject.

You can later also check Google I/O's excellent talk for "Best Practices for Architecting GWT App"  http://www.youtube.com/watch?v=PDuhR18-EdM

So, if we follow the MVP design pattern and Google's best practices (even if we don't use GWT),
we end up with few key components in our app, i'll try to give some description what they do:

1. "The" Event Bus - The component where presenters 'listen' to, and can fire events to.
2. The Presenters - The components which encapsulate the logic of your application.
3. The Views / Displays - Simply a view - can be a panel with widgets in it. No logic in here!
4. A Model - Where you keep important data that can be accessed by one or more presenters.

"Show me the code!"

Lets assume you're writing your rich client in Java Swing.
We will use the lightweight DI framework "Guice" by Google:
http://code.google.com/p/google-guice/ to help us achieve our goal.

Lets go over some steps to realize what needs to be done in order to get this to work - don't forget to download Guice and put it's Jars in the classpath.
(Or, scroll all the way down to download the zip file containing the source code).


1) Define a simple View as a dumb object, not knowing anything about logic:

public class ContentPaneDisplay extends JPanel { .... }

2) Define a high level IPresenter interface and the IContentPanePresenter interface:

public interface IPresenter {
/**
* A method of all implementing presenters for presenting themselves on a given container.
* @param c
*/
void go(Container c) ;
}

public interface IContentPanePresenter extends IPresenter {}

3) Define a Presenter that will use view object above as its display:

public class ContentPanePresenter implements IContentPanePresenter {
public static interface IDisplay {
JComponent getAsComponent() ;
}
private final IDisplay display ;
....
}

4) Make ContentPaneDisplay implement the ContentPanePresenter.IDisplay interface.

5) Configure the Display class and the Presenter class to be used by Guice:

public class ApplicationDIModule extends AbstractModule {
@Override
protected void configure() {
// Lets configure some stuff !
bind(IContentPanePresenter.class).to(ContentPanePresenter.class).in(Singleton.class) ;
bind(ContentPanePresenter.IDisplay.class).to(ContentPaneDisplay.class).in(Singleton.class) ;
}
}

6) Add the @Inject annotation to the ContentPanePresenter to be injected the display:

/**
* C'tor
* This is where DI takes place!!!
* Guice will instantiate and provide this presenter with a matching display!
* @param display
*/
@Inject
public ContentPanePresenter(IDisplay display) {
this.display = display ;
...
}

7) Now all that's left is to call the Guice injector to get the ContentPanePresenter:

private static void go(Container container) {
// Guice.createInjector() takes your Modules, and returns a new Injector instance.
   Injector injector = Guice.createInjector(new ApplicationDIModule());
// lets get the 'Main' content pane Presenter !!
   IContentPanePresenter contentPanePresenter =
                                                            injector.getInstance(IContentPanePresenter.class) ;
contentPanePresenter.go(container) ;
}