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Radical modularity in Java [closed]

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The development team I'm a part of wrote and still maintains a codebase of pure Java spaghetti code. Most of this was implemented before I joined this team.
My background is in Python/Django development and the Django community really emphasizes "pluggability" -- a feature of Django "apps" (modules) which implies mostly "one thing and one thing well", re-useability, loose coupling, and a clean, conscious API. Once the Django team I once worked in started to "get it", we pretty much had zero problems with messy, tightly-coupled masses of monolithic code.
Our practice involved developing Django apps outside of the Django project in which we intended to use the app (a common practice among Django developers, from what I've gathered) Each even lived in a Git repository separate from that of the overall Django project.
Now, we're presented with an opportunity to refactor much of our spaghetti code, and it seems to me that some of what I learned from the Django community should be applied here. In short, I'd like to see our new codebase developed as a series of "pluggable" modules each written under the assumption that it won't have access to other modules (except those on which it should rationally depend). I believe this should do a good job of driving home principles of proper software design to the whole team.
So, what I'm advocating for is to have one separate repository per "feature" we want in our new (Spring) project. Each would have its own, independent build process and the result would be a .jar . We'd also have a repository for project-level things (JSP's, static files, etc) and its build process would produce a .war . The .jars wouldn't be placed inside the .war, but rather be treated as Gradle dependencies (the same way third-party dependencies would be.)
Now I have to sell it to the boss. He's asked for some example of precedent for this plan. Obvious places to look would be open-source projects, but if a project is split across multiple repositories, it's likely to be multiple projects. So, perhaps I'm looking for some sort of suite. Spring itself looks promising as an example, but I haven't been able to find many others.
My questions are (and sorry for the long back-story):
Is there any such precedent?
What examples are there?
Is there any documentation (even just a blog post would be of help) out there advocating anything like this?
Any suggestions for implementing this?
Is this even a good idea?
Thanks in advance!
Edit: Whether or not to refactor is not in question. We have already decided to make some drastic changes to most of our code -- not primarily for the purpose of "making it cleaner" in fact. My question is about whether our planned project structure is sound and how to justify it to the decision-makers.

The following issues are more important that where to put code on the disk or in an artifact:
If you don't understand that, you have already failed.
What you describe is not refactoring, it is rewriting using a more palatable name:
Unless you have 100% code covered in unit tests already; someone(s) are going to get fired over this when ( not if ) this effort fails spectacularly, probably multiple times!
Even with awesome unit tests, someone is going to miss something and someone is going to take the fall when it finally gets discovered in production, usually after months of silently corrupting data.
Semantics are Important:
Removing Struts and replacing with Spring is not refactoring is rewriting by definition. Refactoring would be moving from Struts 1.1 to 2.0, replacing Struts means replacing all the Struts code with something else, by definition that is rewriting not refactoring.
Working Software comes in many disguises:
The business always thinks what they have is working.
Miss a deadline, introduce a bug no matter how minor, lose a feature no matter how minor, mis-interpret an undocumented process and change something no matter how minor or even for the better. They are just looking for any problems weakness or potential trouble to spread FUD and make sure your effort is a failure, at least most of the time.
All these things will cost you and your team political capital, someone will take the fall for these things, no matter how innocent or merit-less the perceived failures are!
Projected outcome:
Most likely you and/or other "non-Java" developers and not the core Java people that created this working system that you "non-Java" people refactored ( code word for rewrite in this case ) and delivered on time broken and incomplete or didn't deliver on time or didn't deliver at all.

I think it's possible to find examples of good and bad implementation in both Java and Python.
Spring is indeed a good place to start. It emphasizes good layering, designing to interfaces, etc. I'd recommend it highly.
Spring's layering is "horizontal". If "module" means "business functionality" to you, then multiple modules will be present in a given layer.
Plugable suggests a more vertical approach.
Maybe another way to attack it would be to decompose the system into a set of independent REST web services. Decouple the functionality from the interface completely. That way the services can be shared by web, mobile, or any other client that comes along.
This will require strict isolation of services and ownership of data sources. A single web service will own/manage a swath of data.
I'd recommend looking at Michael Feathers' book "Working Effectively With Legacy Code". It's ten years old, but still highly regarded on Amazon.
One thing I like about the REST web services approach is you can isolate features and do them as time and budget permit. Create and test a service, let clients exercise it, move on to the rest. If things aren't too coupled you can march through the app that way.

Refactoring entire application is not an easy task, specially if the code is hard-wired as you have described. If Pluggablity is an important target, I would recommend Grails/Groovy.
If you can somehow identify view, controller and business logic, or much better services. You might be able to reuse some existing codes. The good thing about grails/groovy is that you are able to incorporate JSP/JAVA with GSP/GROOVY.
Again, this is really hard to sell and grails is probably a good framework to ease the refactoring pain.

I would recommend watching "Four Strategies for Dealing with Legacy Code" by Eric Evans, the originator of Domain-Driven Design: http://dddcommunity.org/library/evans_2011_2/
It may not entirely answer your question but it offers arguments and strategies that might help with your endeavour.

Every component is in its own jar, but the jars are not contained in the war ? How should that work ? Even third party libs are included in the war. Except for those that are provided by the container. Regarding the jsp stuff: Can I serve JSPs from inside a JAR in lib, or is there a workaround?

Comparison between GWT and Spring MVC

I was wondering if someone who was experienced in both technologies could give an objective comparison between the two, assuming you were building a complex web application that would be both very rich in on the server and in the browser.
One problem with the older paradigm, for me, is testability of the Spring MVC layer. I find that there's a lot of bugs that can creep into your application due to untestable annotations. This model also slows development cycles because you have to restart the server to make changes to the annotations/controller code... which is something I personally find very annoying.
I also don't want to deal with the complexity of javascript. Working with and testing an application all in Java sounds appealing to me. I don't really want to master another language, and learn all of its quirks, weird design decisions, idiosyncracies and the full history of browser incompatibilities.
So for a complex application, would GWT offer a superior approach? Are there any serious limitations to this approach over Spring MVC, which would probably be more flexible although harder to work with? Are there any gotchas and road blocks that are common for building complex applications?
I would really appreciate a comparison between the two. Please keep in mind that I have no experience with GWT, but about 10+ years experience with Spring. Thank you!

The truth is that also GWT has a learning curve and also at least at the time I looked at it, two years ago, you're not doing much with the basic controls, you need external libraries and that means more learning.
After trying to learn GWT without much success, I opted for a webservice plus either jQuery or ExtJS, which also gives a very clean separation of the roles. I sat down and learnt JavaScript, it wasn't easy but it was immensely more fun than using GWT.
As for browser compatibility, once you use a modern library, you'll have very few of them. My code works in all browsers without too many problems, including IE 6. Also when I am too busy, I write the services only and outsource the JavaScript interface part, which allows increased productivity.
Anyway, this is fairly subjective, another person fluent with GWT, can have an opposite point of view of mine. I will anyway reject the following reasons:
ease of debugging. Not true anymore: it's very easy to debug JavaScript with FireBug, plus there won't be any business logic in JavaScript, only services call and display.
browser compatibility. There are very few quirks to remember, the most common one is that IE doesn't accept trailing commas in lists, which is anyway not in the standard, but Firefox tolerates them. Any modern JavaScript library will take care of compatibility for you.
Speed. To start with I will state that JavaScript is very fast for any reasonable computation within the browser. What is slower is DOM manipulation and of course anything involving the network, like AJAX calls. Your page will perform just right if you don't do design mistakes, like stuffing too many things or other problems that can arise when adding many elements directly to the DOM, instead of building your structure and then attaching it all at once.
As far as I can think now, the only valid reason is, I already know Java, I don't want to study another language.
As for your comment on Spring MVC. I am using Spring MVC and I don't feel the pain of restarting the server. The whole point of Spring is that everything should be easy to work with outside the container! In the Spring controllers I've very minimal code that just call the underlying services. What I need to unit test well are the services.
The controllers have very few code to test, I could just call them and test them within JUnit, but, at least for now, my approach is having a simple external test done through a web page with jQuery calls that check their response (it's not unit test, it's an integration test, but I feel there is a very little value to unit test a controller, if it's written properly).

I am using GWT for more than a year now in a complex project (200 KLOC for the whole project), and I recommend you to give GWT a try.
In my opinion GWT is quite easy to learn, there are really good tutorials about how one should use this technology.
The advantage of using GWT is that one can build nice, fast, maintainable web apps, without knowing very little about browsers or javascript. You can also debug your client side code with a Java debugger and in complex apps this is huge.
Although GWT offers the possibility to properly unit test the client side code, this requires a good understanding of GWT's MVP paradigm and careful planning. If you mess up your code (which is not that hard, because GWT gives you total freedom) then you are going to end up losing this feature, but this is your fault, not GWT's.

It took me a couple of months to learn Spring well enough to create fairly basice MVC apps. It took me about a month to master GWT. (It could be that it was easier because I had already worked with Android for three years and it works similar. It even has the exact same unobvious solutions to some of its problems.) So for me, GWT was definitely much easier to learn than Spring.

JVM Frameworks, which one?

I don't have much experience in frameworks or languages, so i need your help.
Here's what i've done so far so you can understand where i'm coming from.
I've developed a web app using Java/Spring MVC/Hibernate. on the front end i've got some jquery datatables doing ajax calls to a db, another pages executes a stored prod and thats about it.
Now i got fed up with all the configuration, beans, hibernate mapppings, spring mappings, apache tiles, and the list goes on.
I had a play with Groovy/Grails and that seems so much easier, but that means i need to learn groovy and i've heard about it's performance weakness.
So i ran into Play Framework, can someone tell me if Play would make my life easier with the above scenario or should i just go into Groovy/Grails or even scala/lift.
I don't have too much time on my hands to pick up another language so if i can stay with core Java and use Play that would be great.
So is my described headache the reason why there's RoR/python-django, grails ect,ect? or is it something else?
thanks,
glenn.

I can tell you from the perspective of a 10 year J2EE developer who went from JSP/servlet to Grails to Play. 6 years ago I discovered groovy and I liked it very much, I've been using groovy and it's GSP templates in my other projects for code generation. I really love groovy syntax. Because you can do a lot in a single line of code ;) Because of groovy I tried Grails. But, besides the use of the language to code something in perhaps some 20% of the project time, you are 80% dealing with Grails conventions. How do they map this and that and to the persistence layer (which is JPA underneath the surface). So you're browsing the docs most of the time.
Then I found play. It really felt natural. Everything is so quick with it. Everything is direct, it is 80% undisturbed, productive coding, only 20% reading the docs. The code completion of any Java IDE is literally sufficient support. In Grails you either need a Grails IDE or you find yourself frequently browsing the docs.
The biggest attractor of Play to me is the hot code swap feature, which nearly completely eliminates the build phase. Play's class enhancers give you enough comfort to get over the loss of those dynamic finders in Grails. In the meantime, I even write my own enhancers to get even more comfort.
In a real project, the strongly typed Java language is a huge benefit to all developers. You just can't break it so easily as you can with groovy.
Also, if you look at the Play package, you always get reasonable defaults. Things that all developers like. jQuery based CRUD, beautiful code samples, good visual experience. And it's all as minimalistic as possible. Which means, you can always go to the play framework source itself and read the code to understand play's behavior.
So to sum up, after 10 year of Java and J2EE frustration and almost giving up on Java I switched back to it as implemented by Play, because in Play it is so much fun and I now love it again. I recommended play to 2 other developer friends and they love it too. It feels like the Java that it should have been in the first place. Fast, clean, secure & a lot of fun. I will never use something else based on Java, not even for a simple main() ;)

Play!
After 6 or 7 years of Spring/Hibernate, a couple of more with JSP/EJB I was done with the Java world, looking for other alternatives like Scala, Node.js, Rails, etc. Play Framework has made me fall in love with Java all over again, even though I do recommend Scala.
I have lots of information about Play on my blog http://geeks.aretotally.in and http://playframework.info.
It's super easy to pick up, it's crazy productive and you will have lots of fun!

If you ask a Play framework guy, he will tell you to use Play. If you ask a Scala/Lift guy, he will tell you to use Scala/Lift.
Ideally you'd like to find someone who has used Groovy/Grails, Scala/Lift, and Play, but unfortunately there are not too many of those around.
FWIW, I use Groovy and Grails, and like it a lot. If you already know Java, Spring, and Hibernate you already know most of what you need to be productive with Groovy/Grails.
If you don't want to spend a lot of time learning a new language, I'd stay away from Scala, as it's a very different language to Java, whereas Groovy is almost a superset of Java, and with a familiar syntax.
I know virtually nothing about Play, but I'd be concerned about the size of the community - check the number of Play and Grails questions on stackoverflow for a rough comparison.

Grails 2.0 performance will be pretty much on par with the static typed languages out there.
Based on your current architecture, Grails would be the most natural fit - you can re-use all existing classes and code without an issue, and have it directly picked up. You can freely use #Autowired and other Spring annotations, java code, and Grails picks it up - because Grails is Spring under the covers. The only part that might need a little tweaking are JSPs, but I was able to get existing JSPs and custom taglibs working without an issue. Grails uses SiteMesh to compose it's Groovy Server Pages (think JSP groovy-ized, and removing some of the JSP restriction gotchas).
Nothing against Play, Lift, Clojure's web framework, SEAM, or any of the other frameworks out there -- but if you want a simple transition from what you have to something a little more productive, then Grails would be the closest fit.
Of course these days, just about every one of those frameworks supports polyglot programming - you use Scala for something, Groovy for something else, and Java all around - compilers, build environments, and tools are all addressing polyglot development.
Long story short, it comes down to requirements and risk management - do you need functional programming, dynamic typing, re-use of your Spring controllers, or just some simplification and productivity boosts?
Even a simple Spring 3.1 upgrade may eliminate some of your XML files for annotations and solve most of your problems.
Happy Hunting!

Java Time Savers [closed]

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I find the nature of this question to be quite suited for the practical-minded people on Stack Overflow.
I'm setting out on making a rather large-scale project in Java. I'm not going to go into specifics, but it is going to involve data management, parsing of heterogeneous formats, and need to have an appealing interface with editor semantics. I'm a undergraduate student and think it would evolve into a good project to show my skill for employment -- heck, ideally it would even be the grounds for a startup.
I write to ask you what shortcuts I might not be thinking about that will help with a complicated project in Java. Of course, I am planning to go at it in Eclipse, and will probably use SWT for the GUI. However, I know that Java has the unfortunately quality of overcomplicating everything, and I don't want to get stuck.
Before you tell me that I want to do it in Python, or the like, I just want to reiterate why I would choose Java:
Lots more experience with algorithms in Java, and there will be quite a bit of those.
Want a huge library of APIs to expand functionality. ANTLR, databases, libraries for dealing with certain formats
Want to run it anywhere with decent performance
I am open-minded to all technologies (most familiar with Java, perl, sql, a little functional).
EDIT: For the moment, I am giving it to djna (although the low votes). I think all of your answers are definitely helpful in some respect.
I think djna hit better the stuff I need to watch out for as novice programmer, recognizing that I'm not taking shortcuts but rather trying not to mess up. As for the suggestions of large frameworks, esp. J2EE, that is way too much in this situation. I am trying to offer the simplest solution and one in which my API can be extended by someone who is not a J2EE/JDBC expert.
Thanks for bringing up Apache Commons, although I was already aware. Still confused over SWT vs. Swing, but every Swing program I've used has been butt ugly. As I alluded to in the post, I am going to want to focus most on the file interchange and limited DB features that I have to implement myself (but will be cautious -- I am aware of the concurrency and ACID problems).
Still a community wiki to improve.

Learn/use Spring, and create your project so it will run without a Spring config (those things tend to run out of control), while retaining the possibility to configure the parameters of your environment in a later stage. You also get a uniform way to integrate other frameworks like Hibernate, Quartz, ...
And, in my experience, stay away from the GUI builders. It may seem like a good deal, but I like to retain control of my code all the time.

Google-collections:
http://code.google.com/p/google-collections/

Joda Time for all date and time manipulations.
One of Hibernate or iBATIS to manipulate data in a database
Don't forget the IDE: Eclipse, Netbeans or IDEA if you have some cash and like it

Apache Commons has a lot of time saving code that will you most likely need and can reuse.
http://commons.apache.org/

A sensible build and configuration platform will help you along the way, Ant:
http://ant.apache.org/
or Maven (preferably):
http://maven.apache.org/
Especially as the size of the project, and the number of modules in the project increase.

There's getting the "project" completed efficiently and there are "short cuts". I suspect the following may fall into the "avoiding wasted effort" category rather be truly short cuts but if any of them get you to then end more quickly then I perhaps they help.
1). Decomposition and separation of concerns. You've already identified high-level chunks (UI, persistence layer, parser etc.). Define the interfaces for the provider classes as soon as possible and have all dependent classes work against those interfaces. Pay a lot of attention to the usability of those interfaces, make them easy to understand - names matter. Even something as simple as the difference between setShutdownFlag(true) and requestShutdown(), the second has explicit meaning and hence I prefer it.
Benefits: Easier maintenance. Even during initial development "maintenance" happens. You will want to change code you've already written. Make it easy to get that right by strong encapsulation.
2). Expect iterative development, to be refining and redesigning. Don't expect to "finish" any one component in isolation before you use it. In other words don't take a purely bottom up approach to developing your componenets. As you use them you find out more information, as you implement them you find out more about what's possible.
So enable development of higher level components especially the UI by mocking and stubbing low level components. Something such as JMock is a short-cut.
3). Test early, test often. Use JUnit (or equivalent). You've got mocks for your low level components so you can test them.
Subjectively, I feel that I write better code when I've got a "test hat" on.
4). Define your error handling strategy up front. Produce good diagnostics when errors are detected.
Benefits: Much easier to get the bugs out.
5). Following on from error handling - use diagostic debugging statements. Sprinkle them liberally throughout your code. Don't use System.out.println(), instead use the debugging facilities of your logging library - use java.util.logging. Interactive debuggers are useful but not the only way of analysing problems.

Don't discount Swing for the GUI. There are a lot of good 3rd party Swing libraries available (open source and commercial) depending on your needs e.g.
JGoodies Form Layout
SwingX
JFreeChart

Use logging framework (i.e. Log4J) and plan for it. Reliable logging system saves a lot of time during bug fixing.

For me big time-savers are:
use version-control (Subversion/Git)
use automatic builds (Ant/Make/Maven)
use Continuous-integration (Hudson/CruiseControl)
the apache-commons-libraries are very useful

Test Driven Development
Figure out the functionality you want and write tests to demonstrate the functionality. Then write just enough code to pass the tests. This will have some great side effects:
By writing just enough code to satisfy your requirements you will not be tempted to overbuild, which should reduce complexity and make your code cleaner.
Having tests will allow you to "refactor with confidence" and make changes to the code knowing you're not breaking another part of the system.
You're building quality in. Not only will you have assurance that you code "works, but if you really want to use this code as a sort of "resume" for potential employers, this will show them that you place a lot of value on code quality. This alone will set you apart from the majority of the developers out there.
Aside from that, I would agree that other big time savers are Spring, having an automated build (Maven), and using some form of source control.

For data persistency, if you're not certain that you must use SQL, you should take a look at alternate data-storage libraries:
Prevayler: an in memory database systems, using developing ideas like "crash only components", that make it easy to use and very performatic. May be used even for simple applications where you just need to save some state. It has a BSD License.
BerkleyDB Java Edition: a storage system with different layers of abstraction, so one can use it as a basic key-value storage (almost an in-disk hashtable) to a fully transactional ACID system. Take a look at it's licensing information because even some commercial software may use it for free.
Be aware that they have trade-offs when compared with each other or with a standard SQL database! And, of course, there may be other similar options around, but these are the ones I know and like. :)
PS: I was not allowed to post the respective links because I'm a new user. Just google for them; first hits are the right ones.

You can save time between restarts by using JavaRebel (commercial). Briefly, this tool allows you to write your code in Eclipse and have the code changes picked up instantly.

Spring Roo can not only get your project quickly kickstarted (using a sound architecture) but also reduce your ongoing maintenance. If you're thinking of using Spring, servlets, and/or JPA, you should definitely consider it. It's also easy to layer on things like security.

Is Grails worth it? [closed]

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This is half rant, half question.
Is it worth using Grails? I'm trying to develop a relatively simple database-driven web application. My expertise is in Java, so naturally Grails seemed like a good choice. At first I thought of using Spring, JPA and Hibernate, but I’ve used that previously and have run into all sorts of tedious configuration and coding work. Grails advertises itself as solving this.
My biggest frustration with Grails is all of the little things that don't work. What I mean is that it doesn't work as one would intuitively think it should. It's very rough around the edges. I run into problems constantly. Sometimes it's my lack of Grails understanding — other times I've discovered legitimate Grails bugs.
One major issue is the lack of good Eclipse integration. There is a Groovy and Grails plugin, but it doesn't do much other than syntax highlighting. Calling Groovy from Java and vice versa is very painful to configure. Not having good IDE support is a major bummer.
What happens is I sit down trying to develop my web application. At the end of the day I realize that I've spent about 85% of the day debugging Grails-related issues. If it isn't Eclipse problems then it's eager loading, fetching in the view, one-to-many relationships, weird empty file bug behavior, a weird property/getter bug — it just goes on and on. This is just a sample of the issues I ran into today. My last sit-down with Grails yielded a whole bunch of different issues.
I sometimes wonder if it's worth it. I'm curious if others have experienced this. Are there people actually using Grails to productively crank out a web application? Are there other frameworks for rapid web development that I should be considering?

We had a team of 12 people all seasoned senior Java devs who learnt Grails from 0.6B and we are all still working on projects based on Grails. I wouldn't go back to Java willingly, and we are all relieved to have broken the back of how to get somewhere quick with a Grails app.
It was a struggle, it was not easy and there was/is frustration.
Nevertheless we delivered something very quickly given our ongoing efforts.. There are bugs, many which have workarounds.
I have heard of several instances of developers who are good at Java trying to dive into deep, complex incantations of Grails projects. We eschewed all Java and went pure-Grails and Groovy. We made sure we started simple, built up the complexity as manageably and as practically as possible.. We dared not dive in the deepest end and hope that our Java knowledge was enough to carry us.
We had eventually created something huge and complex that worked fabulously and did so far faster than writing pure Java/Spring/Hibernate version; and thats without decent IDE support and a far worse situation in terms of bugs than today.
As regards Eclipse support, the only real IDE to use for Grails/Groovy is Intellij - the Eclipse support is way behind, sadly: I was an Eclipse lover and am far from being an Intellij convert - the Grails/Groovy support blow everything else away though.
Yes, Grails is immature compared to Spring perhaps. Or Hibernate. And I would wager that in the first 1.5 years of their existence they were equally as fraught with issue.
That being as it is, places the onus on you, to take care that you keep complexity to the absolute minimum, to carefully test-first (in our opinion) and build up to complexity gradually and with care.
There is no fast code solution with Java once you involve Spring/Hibernate in the stack. The complexity Grails embodies is a reflection of Spring's / Hibernate's own complexity. If you feel that you time is better spent doing it with pure Java, I wouldn't argue otherwise.. I still have my WTFs but now that the steep learning curve is behind me I think I will stick w Grails some more.

I very much enjoy writing grails application for two reasons:
I don't have to use Java
I can use Java
I think after having become familiar with grails one gets his things done very quickly and elegantly.
So much for the plus side. The minus side is performance, which hits me on two aspects: deployment and testdriven development.
I haven't managed to run more than 3 grails applications on a single (rented) server, because I quickly hit the memory and performance limits. There are simply too much frameworks included.
Plus, the testrunner of grails isn't worth that name. When I run unit tests, they should be done in an instant, not in 10 to 20s. So I find myself all the time writing business logic in plain java, because I can test it much faster. But I guess that this can be addressed with a better integration into the IDE (eclipse).

I think Spring's support of Grails is going to be a big boost. If anybody can move it past CRUD on the web, it's those guys.
I also think it's reaching a critical mass. There are several new books that will be hitting the market in 2009. I think those will help the adoption rate.

I fully agree with the original posters sentiments.
We are a Java + Spring shop and took the opportunity to try out Grails.
We first created a very small test application which turned out to be pretty simple to do and it worked pretty well. The main issues we had here were due to our lack of knowledge with Groovy and Grails.
Following this success (confidence boost) we decided we would attempt a slightly larger project. This has been a much more painful experience. As mentioned by others, we have uncovered all sorts of bugs and issues which were not immediately apparent on the surface. The app restart cycles get extremely painful and unless you have really good test coverage its a nightmare to do any sort of re-factoring.
Really frustrating is having code fail without a single error message! It just does not work and you don't know why?
I like the ease of use of plugins for JMS, Quartz and Remoting to name a few. Does away with a lot of tedious XML.
I almost like GORM for its simplicity though we have had several issues as well.
I don't like the loosely typed nature of Groovy and the fact that you have to run your application just to be able to catch a bunch of errors, reminds me too much of PHP or Rails.
At the end of the day we are asking ourselves if its possible to write a complex piece of manageable software using Grails...
We have a Grails application about to go into production....so we will see.

We are using grails + on the web layer + java with hibernate and spring on the service layer. It's the classic three layers (web, logic, data) where the web is grails and the logic is implemented in java. As is usual in java, we use bean objects that represents the data between different layers.
It works pretty well and it was the best solution for our case as the bean objects were already there, as well as the database structure. From our experience, I think grails has a great value as the web presentation layer, but I would stick with java to write the business rules and to persist the application data - as grails "is" java, all the grails-java integration is pretty straight-forward.
We use eclipse to develop the grails application and it's poor integration, as people said in here. But, as a suggestion from other developer, we run the grails application from the command-line and only use eclipse to save the source files, and it works pretty well, as the application is updated on the fly.
I yet don't feel comfortable for using grails in other places than in the presentation layer.

I have a lot more experience with Ruby on Rails than I do with anything in the Java world, so I'm coming in from a different perspective. Overall, Grails is much more rough-around-the-edges than Rails is, partially due to its immaturity, and partially because it relies on two insanely complex frameworks under-the-covers (Spring and Hibernate). Rails also has a much bigger community.
But, Groovy as a language has made huge strides, and is a pleasure to work with. Thanks to the improvements made in Groovy 1.6, Grails is quite a bit snappier than JRuby on Rails, and you get amazingly good XML support via GPath. There's a lot of nice features you get by being on the JVM (like concurrency and tons of threadsafe code), but without having to muck about with Java (a language I don't much care for), so I'm having a really hard time of convincing myself to use anything on MRI.
Python is looking tempting, though, I must admit.
As for your Eclipse problems, I can't help. I use Vim and Emacs, mostly because I can't stand using IDEs. For dynamic languages like Groovy, Ruby, and Python, though, I don't think IDEs really introduce any real benefit, as there isn't really any place for code generation, or a need to compile. Maybe try working sans IDE for awhile and see if things are smoother?
So, yeah, I think Grails is worth it. They've done a helluva job in getting things working as quickly as they have, and the Grails and Groovy teams are both really, really dedicated.

I am totally with you! Grails still feels so rough around the edges that it's almost a joke to compare it with Rails. If at least the error reporting was a little bit better. But I guess that's probably also due to the huge amount of libraries that it uses under the covers. One word: stacktrace! I am also not a big fan of the model->db approach (Rails has db->model). The scaffolding also leaves much room for improvements. Then "no restart required" also does not work as advertised. (I am not sure what's worse - having to restart all the time or sometimes finding weird behaviors that go away when you do restart) And don't get me started on GORM. (When it takes hours to find a way what would have been a simple SQL you start to wonder whether this whole ORM really saves you time) Maybe as long as it is simple.
I mean: it's still one of the better choices of a framework when you are coming from the java world. (So much useless crap out there that calls itself a web framework) ...it has potential. I just wish it wouldn't have build on top of so much other complex stuff.
Anyway - let's hope these things get sorted. At the moment I am lurking at playframework.org which also looks very slick and promising.

It will be worth it when they finish the eclipse plugin. The sooner the better I say. Trying to sell groovy to my boss isn't going to be simple until that happens.

I find that the biggest advantage of Grails is that I don't have to care about the database anymore - the schema is automatically created / updated, and the persistence is largely done for me (no more writing SQL queries). This is a huge relief. The other thing that is rather nice is that once you settled on the templates for controllers and views, adding new domain objects is pretty fast. Although I suspect that you will do ongoing changes for your views at least, back-fitting them to the existing ones.
As for the IDE - it seems that IntelliJ is the best option, but I'm happy using Netbeans 6.5. I use MyEclipse for all other development, but Netbeans just has better Grails support now.

I was an Eclipse user before I started using Grails. It was quickly apparent that wasn't going to cut it. So I tried Intellij and NetBeans. At the time Intellij was better as far as Groovy and Grails were concerned. However, NetBeans was free and that made it good enough for me. Since then all three have had new versions or new plugins released. I am still using NetBeans because of the cost of Intellij. With the acquisition of G2One by Spring Source one of the expectations is more support for Groovy and Grails in Eclipse. This will be necessary for increased adoption.
Using Grails for a new project is wonderful. So much of the Enterprise Java baggage is no longer necessary. I can imagine trying to port something would be difficult because until you understand where a framework strength's and weaknesses are it is hard to utilize it efficiently. It is promised that JSP support will come easier in Grails 1.1, I don't know if using a beta version while trying to grok a new framework is a good idea. The testing has also gone through a major revision for the new version. If time allows you may consider waiting as the 1.1 release should be very soon.
If you have an opportunity to give Grails a try in a different IDE when starting a project from scratch I think you will see it in a different light.

I have just started using grails on a new project...not having to write ANY xml files yet still have the power of Spring and Hibernate is truly amazing.
Use IntellijIDEA for the IDE though, I actually discovered Grails through the IDE (I might be biased though, I hate eclipse).

Totally. There are so many Java frameworks that the bar is set quite high for newcomers, and it's a testament to Grails that it was able to rise above in such a crowded space.
It still has a few edges that are sharp, but those are just a matter of time before they're matted down, the underlying project is VERY much worth it.

Grails might be to big for your type of application (based on the numerous files it created on the first initialization and the resources it takes). If you're looking for something simple, Grails might not be what you're looking for. If you are looking for something simple and works, so far I reckon django can do your job well. Take a look at how simple (how many files it requires) to create a CRUD apps from its tutorial. From here, your apps can (relatively) easy to scale as your needs and requirements grows.

I'm not sure they will ever be able to make Grails right you know. And by right I mean address all the details (small and big ones) which in the end makes it feel brittle and fragile. I'm not even sure that there is a real development team (meaning more than 2 people) behind it.
Every single time I iterate over a feature of my Grails projects, trying to improve something, it is the same workflow: everything falls apart, then it's a hundred of 'google' test cycles, then you find out the reason you can't do what you want and you do something else.
In the end, you're frustrated because you don't even want to touch anything that runs. And things that don't well, you drop them!
I'm considering a switch to Rails via JRuby. That may be the best of both worlds: a capable web framework with an active and large community, a dedicated team of developers, a platform which is not based on questionable and complex frameworks like Spring or Hibernate, a quick and ambitious release cycle. And JRuby because frankly, so many Java assets in my backpack, I can't just throw them away.

If your expertise is in Java as you say. You should have a look at Play Framework - it's a web framework inspired by Ruby on Rails with a very short development cycle - just save your Java source file and update your web browser. And if you want to try another language, Play Framework has a module that let you use Scala instead.
I like Play Framework since it's easy to understand and has good performance. You can also use JPA and Hibernate for the ORM-layer if you want.