Develop Reference

Google Web Toolkit Sample Applications

I have googled some time now trying to find a good sample application that is written with the Google Web Toolkit (preferably with Eclipse). I'm looking for a full web application with a database and stuff like the following program on codeplex which is written in ASP.NET and has a login system:
http://mvcmusicstore.codeplex.com/
I found some other sites but they do not contain the exact details that I need:
http://code.google.com/p/gwt-examples/wiki/project_MySQLConn
http://code.google.com/intl/nl/webtoolkit/examples/
I want to learn GWT because I think it has some great advantages.
Generate (good and cross-browser compatible (>IE6, >FF~2.0, >chrome1)) JavaScript at the server-side for the client that will save CPU cycles on the server
Use Java at the server (instead of C# with ASP.NET) which is free to use and deploy, and is a good OO language
Program and test in other OS's than windows (LAMP server, free :) )
Out of the box HTML5 support which can be used as a replacement for flash/silverlight animations to save bandwidth
Eclipse has a visual designer plugin (GPE) where you can put widgets on and works like WPF/Silverlight where I have already some experience with
The widgets are great and I expect them to work like the WPF/Silverlight equivalents (stackpanels, grids etcetera)
Google uses it (so it must be great :P )
Some disadvantages in my opinion:
No good support for VS2010 (super IDE of course)
Not as many users as ASP.NET or PHP (?) so less good code examples to find
Not many I think? Maybe some little debug difficulties because of the generated JavaScript
Please criticize this as much as possible ;)

GWT projects are almost identical to other Java-based web applications. Client side has the major differences (and limitations therefore) of course, but everything else is pure Java. Maybe it would be better to start off by learning Hibernate, servlets and such? Find out the best techniques for You and then dig into GWT.
EDIT: I found a really detailed GWT tutorial http://www.vogella.de/articles/GWT/article.html

What are the pros and cons of using webworks versus J2ME and vice versa in blackberry development?

I have written some basic applications using J2Me and felt that getting things done in terms of UI/UX were a night mare especially with blackberry OS 5. I then started playing around with Webworks and found it to be better and faster however i keep getting told that it is better to stick with J2ME. Which one is a better choice? Is one limited in features than the other? What will RIM support for the long term future?

This is a decision to be made for each application.
How well do you know HTML, Javascript, and CSS? How much device integration do you need? How graphics intensive will the application be?
HTML et al have a much lower learning curve than J2ME and the RIM APIs. You are missing some of the more functionality that integrates deep into the phones abilities. But you have a distinct advantage in that anything that you find missing in the Webworks libraries, you can write as Javascript extension in Java.
Webworks itself is limited to the blackberry platform, but HTML, Javascript, and CSS are practically universal. It's simple to turn the application into something that will work in a web browser. Just take out Javascript calls to any blackberry.* apis (or wrap their use in blocks like if (blackberry) {), and redirect anything in an XMLHTTPRequest to be proxied through something on the local server. I'm doing it this way for a Playbook app I'm working on. It's nice that I can show others that don't use a BB the functionality of my app.
It's probably pretty easy to take your Webworks app and alter it for another framework like Adobe AIR or PhoneGap (I haven't tried, but intend to at some point).

From experience, Webworks seems to be easier to develop in terms of UI. But in terms in functionality, there isn't much. I don't know if they've changed this, but before, if there wasn't specific functionality in Webworks, you could create your own by porting the Java code over and creating your own extension.
I would say that using J2ME, would be the better choice if you need more integration with device functionality, rather than UI.

What are the options for developing powerful browser hosted UI in Java?

I am interested to widen my horizons and wish to learn what are the options for developing a powerful browser hosted UI in Java. All I know is .NET based solutions, specifically Silverlight, which I find extremely powerful, although not without some regretful omissions as compared to its elder brother - WPF.
So, to rephrase my question. Are there mature Silverlight alternatives in Java?
Thanks.
P.S.
I am not starting the war of Java vs .NET, so please do not raise the benefits of Java against .NET in general. I am interested in a specific area only, anything else is put aside.
Please, do not bring Adobe AIR, flex, HTML5, etc... The questions is about Java.

The question is about Java, but front-ends for the web are almost never written in pure Java.
GWT - that's where you write pure Java which is then translated to javascript and html automatically
JSF - you reuse rich components to create your pages. Still there's html and javascript. This resembles the ASP.NET model
Vaadin - heard of it, never used it. Seems promising
ZK - Same as above.
jQuery - yes, this has nothing to do with Java, but is very powerful tool for creating rich UI
Flex - easy integration with Java back-ends. (I personally don't like Flex, but it's a viable option)
(I specifically omitted JavaFX, because in my opinion it is not yet mature)

You know, having rich applications in the browser using Java has existed since, say, 1999 : applets, that's what they're for.
They were long far from beautiful. However, with the recent apparition of JavaFX, they can now have a very nice look.

The closest thing to Silverlight in the Java world is JavaFX. I haven't worked with it myself though, and I don't think I've randomly come across any sites using it in the wild... which means your users are less likely to have whatever plugin is required... and you're likely to be cutting out most mobile users too. (I believe there's a mobile flavour of JavaFX, or at least one planned, but you really want to find out whether it exists on iPhone/Android/(whatever your target market is).
Personally I would probably try to stick to HTML 5 and JavaScript, which can still be pretty rich. (That doesn't necessarily mean writing all the UI by hand, of course - projects like GWT and jQuery are your friends.)

Open Laszlo is worth a look they have a nice interactive demo section too.
The OpenLaszlo platform consists of the LZX programming language and the OpenLaszlo Server:
LZX is an XML and JavaScript description language similar in spirit to XUL, MXML, and XAML. LZX enables a declarative, text-based development process that supports rapid prototyping and software development best practices. It is designed to be familiar to traditional web application developers who are familiar with HTML and Javascript.
The OpenLaszlo Server is a Java servlet that compiles LZX applications into executable binaries for targeted run-time environments.

I'm not sure if it fits your demand but have you looked at the Google Web Toolkit? It compiles Java to javascript and some colleges have made nice UI's with it.

I've used GWT before and more recently Vaadin which I would recommend. You can give it a go at a demo sampler here. I am currently using it to create custom portlets for the Liferay CMS/Portal and I am pretty happy with it.

How to rapidly build a Web Application?

To build a Web Application, what kind of open source web application frameworks / technologies are currently present that would be:
Faster to learn.
Ease of use.
Have widgets for rapid development(From a GUI perspective).
Database integration.
I would want this web app to communicate to a Java client.
I am not bound to Java on the server side and free to try out any good rapid application framework.
To summarize, I haven't done much work for the server side hence am not conversant with the tools and technologies for the same.
What would you suggest?
Any and every input would be welcome!...

There is no single "right" answer to this question. As a Java programmer of some 10+ years when asked this question my usual answer is... PHP. There are several reasons for this:
Low resource usage (Apache, nginx);
Cheaper hosting;
Really low barrier to entry;
It's really Web-oriented rather than being general purpose that can be used for Web (like Java);
The fact that PHP scripts aren't persistent (like Java servlets are) between requests makes them much more forgiving and less likely to cause memory leaks and other problems;
No deployment step (like Python, Perl, etc). I'd say this is about the best thing about dynamic scripted languages. Just save the file and click reload on your browser;
PHP might be inconsistent in syntax and several other things but it's also mature and used by some really large sites on the Web (eg Facebook, Yahoo, Flickr, Wikipedia);
PHP is by far the most popular Web development language.
Widgets can be done by any manner of Javascript frameworks like YUI, ExtJS, SmartClient, jQuery UI, etc;
PHP fits well with MySQL.
That being said, a lot of these apply to other languages too (eg Python/Django).
I don't think you necessarily need a framework for PHP but if you do I'd look at one or more of:
Kohana: it's like a more modern version of the more popular CodeIgniter;
Zend Framework: it's modular so you can use as much or as little of it as you like;
Smarty: it's a powerful templating system.

Django has a few notable 'rapid' items including automatically generated administrative interface, bundled ORM (lowers dev time by not having to write SQL and some other code), and a large community with several re-usable apps.
Where Django (or Ruby on Rails or any other MVC framework for that matter) isn't going to be rapid is the learning curve when you first come to developing on them. Django (and RoR) have quite a bit of seperation-of-concerns and if you're not used to that sort of environment, it takes a while to learn the framework. If you're using an ORM that's something to get used to as well, and then of course for any framework you go with there's the API to learn as well.
PHP on the other hand is a little more intuitive in terms of where you put the code and how pages make up your web app. It'll basically let you slap code wherever you want so in the beginning it will probably be faster. In the end it will be quicker but your final product will be sloppier and probably require re-factoring later on.
This comes down to a question of what's the use of the framework. If it's for a hobby site, just go with what's easy (php), otherwise you might want to consider a well-supported MVC framework.
As others have pointed out, jquery is probably the pick for pre-made GUI widgets.
Edit -- And apparently now Django (as of 1.1) has a very awesome set of unit testing tools it comes bundled with. Things like an extended TestCase specifically for Django, a test client (you can do test page request w/o an actual client or server), a tool to give you a % of test coverage you have of the project, and a bunch of other neat stuff.

You've already tagged your question with "java", "php", "python", and "ruby-on-rails", so researching and learning more about those tools would probably help to answer your question.
However, I believe that rapidly building an application is almost never actually the correct goal. Normally, what you want to do is build an application that can be rapidly maintained -- that is, maintained with the lowest possible overall development cost over time.

I would say part of the learning curve will go into understanding concepts. I have been learning about web-apps for some months now, and with my improved understanding of concepts right now, most frameworks show very much similarities. Here are my results so far:
PHP: Great to learn about concepts for doing forms, http-post-requests, http-get-requests. easy interaction with database layer, and it is possible to obtain a working basic application in couple of hours. Almost no hassle with build-systems and web-server configuration.
Ruby-on-Rails: Great to learn about REST and more complicated CRUD applications. Great to learn about the complexity behind MVC and especially simple and powerful interaction with the database layer by using ActiveRecord. Introduction of meta-programming (code-that-writes-code, code-scaffolding) is great. Nice opportunities for free cloud-deployment, e.g. heroku.com and there is a very active community
Java: Powerful interaction with web-server possible (Tomcat, JBoss, ...) MVC is rather complicated here, and in general many configuration-steps necessary (build systems, ORM layer, ...) Grails is a great simplifaction and introduces meta-programming for Java. Jboss Seam introduces REST for Java (but have not looked into this yet)

There are tons, which ones are "good" depend on what you need.
There's Ruby on Rails, which is pretty handy.
For python there's django.
For PHP (I spend a lot of time dealing with PHP), you can look at:
symfony
cakePHP
Solar
Zend Framework
Which are all good in certain situations, and annoying in others.

Speaking only in terms of speed of development, Ruby on Rails is the fastest one out there.

I would vote for Grails.

You can build an runnable Java Web application within 5 to 10 minutes by using the following online Java web application generator:
http://www.webappexpress.net

Client Java vs (Adobe) Flash for web applications, what to choose and when

A few years ago client Java was unsuitable for web development because a remarkable part of web users did not have Java installed. ( I don't remember exact numbers, more than 10%).
Now I see the Google Analytics stats for a big site and it tells that >98% of users have Java installed.
Is these stats very biased by Javascript usage? As I understand Google Analytics measure only users that has Javascript.
Is the picture similar on other big sites?
Does client Java have really "stopper" drawbacks compared to Flash?
EDIT: I mean java applets mainly, java WebStart seems to be not suitable for average user.
I mention Javascript only to describe the way Google Analytics works.

When I wrote my diploma project, I had to choose between Flash and Java Applets. Here are some pros and cons:
Java Applets:
[plus] you program in Java, which is mature and stable
[plus] you can use the Java GUI frameworks that pack a lot of punch
[minus] the first time the user hits the page with the applet, the JVM must be initialized and this can take up to a few minutes even on a fast computer
[minus] Applets are not meant to be used as animation media; sure, you can do stuff, but it is like programming in C - you do everything from scratch
example: i needed to show a data packet as it moved between two routers. The packet must be a control of some sort, like a button or smth. This animation can be defined in 1 line of code in Flash, where all objects derive from some base object that can be animated. I could not find a suitable solution in Java.
Flash:
[plus] really really focused on animations;
[plus] ActionScript is actually an OO language
[minus] ActionScript is sloppy, bughish and has only a few supporters. If you are stuck, be prepared to search obscure Japanese forums for solutions
[minus] ActionSCript may be OO, but it lacks a lot of features, like Enums, fully fledged interfaces, threads (!!!!) etc.
[minus] Flash was designed to be used by non-tech people - they just use the authoring tool; I wrote code for everything and it worked, but it was a pain.
My conclusion:
I eagerly await a programming paradigm for animations and rich client interfaces.
ps: Silverlight seems to be a disappointment so far, maybe Microsoft will inject some $ into it.

Mmm, Java seems to be better supported than I though, I searched some stats and found between 92 and 96% of browsers support Java (ie. it is enabled enough to detect it! although I guess lot of Java detection algorithms use JavaScript to detect & report - as you point out - but JS support is very good too anyway, even more in our Web 2.0 era).
Adobe boasts better support, but overall the difference is rather marginal. Anyway, somebody really wanting to see/use the application will activate/upgrade/download the needed engine.
Now, we have to see what JRE is supported! Alas, I didn't found any stat for that.
There, Adobe have an edge: not everybody have Flash 9 or 10, but upgrading is quite fast. While downloading and installing a new JRE is quite a bigger task... Of course, you can target the historical lowest common denominator Java 1.1, or more realistically Java 2 (1.4), but it is still frustrating not to be able to use all 1.6 features...
I have seen some people complaining that Java applets crashes their browser (apparently on Unix systems) but it is more an issue with a minor number of browsers/systems than anything else.
And as pointed out, startup time of a Java applet is quite longer than for Flash (although some big Flash games are slow to load too).
Now, I have seen a number of Processing applets, like the notorious Webpages as graphs, most of them load quickly: lot of the power is already on the hard disk of the user, in the extensive Java library. Processing generates quite lightweight jars, while lot of Flash applets must include foreign libraries... or reinvent the wheel!

Some previous postings are obsolete in regard to comments on ActionScript. ActionScript3. became available in the Flex 2 time frame, i.e., January 2007 when Flex 2.0 and Flash player 9 shipped.
AS3 is a full blown OOP programming language comparable to Java. It has classes and interfaces, inheritance, access protection keywords for class members, constructors, statics, plus some nice things that Java doesn't have: properties, events, declarative data-binding, and closures.
By default AS3 is statically compiled, hence one declares the type of members and variables. This can be relaxed to where AS3 can revert back to dynamic typing ala JavaScript. It is less efficient at runtime, though. Sometimes when dealing dynamic data it is none-the-less useful to selectively employ dynamic classes. (A nice benefit of static type checked language is code completion in the Flex Builder IDE.)
Much of Flex development is accomplished using MXML. This is a declarative XML-based DSL for Flex. MXML gets compiled into ActionScript3 code, though. So what you do in MXML is equivalent to AS3 imperative coding, but can often be more concise, clearer, and more appropriately structured with respect to the underlying graphical Flex form it represents (i.e., MXML is good for coding the views of the MVC pattern).
The bottom line is that ActionScript3 programming of Flex is easy and natural for a Java or C# programmer to learn. The language is not at all the issue. The power of Flex comes in becoming intimate with the Flex SDK and the myriad capabilities found there.

Not an exact answer, as it would be very opinionated, just sharing my experience...
In a recent project, where we were building a WAI compliant site, we were asked to avoid flash objects as accessiblity was a major issue. Applets on a different note don't go very well with most web developers ;). One reason might be the differences in the paradigms of Rich UI vs. web UI.
However, we found applets to be irreplaceable (not speaking for .NET and ActiveX controls) when client side monitoring was needed. The application uses SmartCard based authentication and applets are loaded into browser to listen for client side events (card removal) and alert the server to end session.
In this context I tend to feel that Flash is meant to be eye candy (view) where as applet though designed to be versatile, takes the role of model on client side. It is to be noted that both applets and flash consume CPU cycles on client machine, hence were traditionally suited for tasks involving lengthy computation. Calculators, Report generators, Trend illustrators, Astrological chart generators (yes) and other tasks where data can be fed by user and are results shown immediately make use of these.
A major concern involves lack of client side software (Java, flash plugins). The user experience in such cases is more than annoying.

Noticed some comments about java not updating itself. Now 1.6.0_10 is out, and it's updating itself more easily and automated than before, and you have the option of a new install method, the java kernel one. This automates the install of java components as you need them.
Some text about this: http://java.sun.com/javase/6/6u10faq.jsp
So there are changes, Sun just wakes up with the new Ceo i think. I know it's 1-2 years until this new system propagates but you can start your project and have fun when it's ready maybe. :) Who knows.
Anyway, maybe you work +500% for easy animated features than flash, but if your app is not a simple animation, then you work +500% with flash for some simple 3 line java code substitution :) Depends on your app.

I worked in Java for the last 7 years, and then I recently started on AS3 on my newest project (1.5 years and going). I love AS3 and Flash, and here's why:
The language itself is very similar to Java. The documentation at Adobe is as good or better than JavaDocs.
The AS3 language supports XML as a native type. Parsing XML in Java is a nightmare.
There are nice animation and graphics frameworks for Flash, such as papervision 3D and tweener.
If you use the Flex 3 framework and Flex Builder 3, building interfaces that look as good or better than Swing is trivial. I loved writing UIs in Swing, but designing UIs in the visual Flex Designer is like a breath of fresh air.
I'm pretty sure that there's more browser support for Flash.
Have you ever seen a Flash applet load? It has really poor usability, and makes your user click through two or three dialogs before the applet starts. Flash apps just work.
Good luck on your project!