Would anyone be able to compare and contrast the two solutions? I don't know much about Seam or JSF, though I am familiar with the way GWT works and very much like the theory of it.
Primary concerns:
Scalability / performance
Cross-browser compatibility
Learning curve
Productivity
WYSIWYG UI building
Capacity to code as much as possible in Java (I can touch JS/HTML/CSS if possible, but preferably not)
Concerning the server-side implementation of your app you have to take the following point into account (pro/con is subjective, so you should decide) when using GWT instead of JSF.
As mention by #z00bs, using GWT you'll have a desktop like app. So you won't use/need page-navigation or page-action feature of Seam.
All requests from GWT to the server are short-running. That means, most of your components will be of ScopeType.EVENT or ScopeType.STATELESS and you don't need/use the conversation scope.
Using GWT instead of JSF reduces the load on the server because you hold most of the state in the client.
You cannot use the JSF/Seam-lifecycle with GWT. For instance, you lose the model validation part in the lifecycle. Model validation will only be triggered by using the entity manager or manually
All other feature, such as security, mailing, or EL, are still working when using Seam with GWT.
Since Seam is well-known for its JSF support, you should consider another framework, such as Spring roo which is strongly related to GWT, too.
Concerning the client-side development of your app we had the same decision to make.
We decided to go for GWT for the following reasons:
Most of the development can be done in java. Since we have a strong background in java development this will save us a lot of time.
We could use all the well known and beloved tools for implementing since all is done in java.
Our app was going to be a desktop like, single page web application without complete page refreshes. At this point GWT seemed to fit best for that need (and it still does).
Pushing most of the state to the client and let him do most of the time consuming processing appealed to us. This way the server can handle lots of simultaneous request and connections to the server are only needed to sync the state on the client.
The support for Unit Testing GWT code is good, in conjunction with the MVP pattern even better.
Since the introduction of UiBinder creating and styling complex UIs has gotten a lot easier and faster.
To your main concerns:
Cross-browser compatibility is mainly taken care of by GWT itself.
WYSIWYG is possible with GWT Designer (I must say I've never used it; I like building the UI myself...)
GWT is really fast because the rendering is all done on the client-side.
Productivity is high when you're used to java.
The learning curve depends mainly on the architecture you use (MVP is complex at first).
Your application will scale since the server is freed of much costly processing.
Hope that helps.
(Some considerations concerning the choice of Seam are coming soon from #kraftan).
The conversation scope offered by Seam can readily be replaced in GWT by storing long lasting transactions (like shopping carts) in memory on the client side.
Neither! dont use seam (or jsf for that matter) if you absolutely dont have to! There are so many better web techs on java.
What are the pros and cons of echo3 framework compared to other java web frameworks?
Echo3 is still under development. Echo2 is stable (but old). The main "pro" is that you don't write javascript or html, you write Java GUI code. The main "con" is that it has not been widely adopted. I've used Echo2 5 years ago and it was a nice framework, but the development of Echo3 is slow (thought it has not stopped).
Perhaps it is worth taking a look at other similar frameworks like GWT or Vaadin.
These (Echo, GWT, Vaadin) differ from traditional frameworks (like spring mvc, struts, wicket) in the fact that you don't write HTML, css and javascript. That's why they are more suitable for highly-interactive web-applications that would resemble a desktop application. If you, for example, need to have bookmarkable URLs, want to rely on browser navigation and such browser-intrinsic things, don't go for Echo/GWT/Vaadin (although they do provide some support for these things)
I went to the Echo3 website and found an argument that discouraged me from testing it. It seems that it is a dead project:
the current version of Echo3 is 3.0.beta8, released August 6, 2009
Technically, I don't know...
Recently the final 3.0.1 version has been released. A 3.1 version (with WebSocket integration etc.) is just around the corner.
The original creator/maintainer has all but dissapeared, but there are considerable community efforts in reviving the project (and make it less dependent on a single (albeit very gifted) person).
Old question, but some people may still ask it...
I've been working with Echo3 for some time now, and the biggest problems are indeed that is is not widely adopted, as already mentioned and that the development progresses very slow.
When choosing a framework, you normally limit yourself to it's technologies, and Echo3 simply lacks a few things that I always missed in my projects. For example, the Echo3 table component offers no scrolling, no pagination and no sorting. And a table is one of the most important a components a framework can offer (Echolot has a nice table component, but it only supports text values and currently has no sorting).
So have a good look at the Echo3 showcase at http://demo.nextapp.com/echo3csjs/ and at the widget libraries at http://echo.nextapp.com/site/echo3/addons and see if that is enough for you.
Also, it changes the way you can design and layout your applications. Echo3 gives you the usual desktop components, like rows, columns, grids and panels. However, it doesn't offer layout manager concepts like Swing does and also does not have any CSS support. When having to follow exact design rules which involve exact positionings and behaviours of components you might have trouble doing this with Echo3.
I would like to write a somewhat complex web gui application.
It will be used to edit certain content by displaying panels and allowing the user to drag items to edit the content.
The explanation is somewhat abstract, but the point is that i'm looking for a modern gui writing technology, the more standard it is the better odds of me finding information and samples to using it.
I've been using JavaFaces to write some simple web pages and have taken a look at RichFaces for purposes of writing the app described above.
I would love to hear recommendation of similar technologies (For example - What was used to write this website?)
Thank you!!!
Update: Thanks for the answers so far, Since I was asked for more clarification I'll try to explain the use of the app:
It will be used to edit a complex script. There will be one panel with the actions of the scripts (The phases) and the other panel will show the content of the currently selected action. To each action type there will be a different set of attributes to modify.
You will be able to reorder actions by dragging them to a new location (Kinda like powerpoint slides organizer or flickr photo organizer) and also copy them that way.
The content of the action attribute panel will be able to display various types of content such as html text and buttons and all kinds of stuff.
Hope that helps. Thanks Again!
Update2: After reading this StackOverflow Thread I'm leaning towards RichFaces for it's vast support and standardization.
It seems you need a RIA. The Java worlds offers the following options:
Google Web Toolkit - a powerful RIA technology, which will require you to go through a steep learning curve. Nice component frameworks are SmartGWT, gwt-ext and ExtGWT. In my opinion all of them have some drawbacks, but in your case you might not observe them.
RichFaces - quite powerful as well, and since you have JSF experience, I'd recommend this.
ZK - never used it and I don't like some aspects of it (at least a while ago when I last checked it), but it's still an option.
Echo3 - similar to GWT in the way of development, but very different in the actual result. I'm not sure, however, whether it's still in development
JavaFX - if you are adventurous, and your application won't be used by the open public, try it.
ASP.NET MVC was used to write this site.
To your question: you should use the technology you like. If you've used to Java, you may wish to explore various MVC frameworks for that. Or you can try out new unfamiliar to you (yet) technologies.
Take a look to GWT and SmartGWT. Together are quite a powerful combination to write RIA webapps.
An interesting framework that I would be glad if I had the time to look deeper into is Cappuccino. Look at 280Slides for an example.
Flex is also nice open source option to create Rich Internet Applications. If you would like to stick to the JavaScript then you can use JQuery, YUI etc
There is also one very interesting thing called Vaadin check it http://demo.vaadin.com/sampler/
ICEfaces is one possibility. Demos here.
I used richfaces including drag and drop functionality, realy nice to offer good usability.
If you like the Java Web Technologies take a look at zk. It promises the same things as ICEFaces. I don't know if it can live up to that promises but IceFaces coul certainly not for me.
ZK should enable you to build your web app like a common swing app.
I'd suggest that you do not invest into technologies/frameworks which are based on integration of browser side ajax capabilities with server side frameworks if you'll need advanced functionality in the browser.
What is advanced and what is not is a completely different topic of course, but just to give you a heads up, as you start facing more and more complex UI requirements, you'll discover that the connectivity to back end framework (like JSF) will become more of a problem than a capability. Especially with things like JSF lifecycle, and most of the server side frameworks being based on the idea of an HTTP post (for client-server communication), you'll have issues.
An example: you'll be requested to develop a very specific UI widget that has drag and drop capability. If the Ajax-jsf integration framework of your choice does not contain this widget, your problem is born at this point. You'll start looking for ways of injecting data into existing channels, and it will get messy.
To avoid further speculation, let me just repeat that if you are sure that your chosen technology setup will give you 90%+ of the capabilities you'll need, that is ok. If you end up developing too much custom stuff, then consider an integration between a powerful client side (javascript or flex or silverlight) layer and a simpler server side layer (resteasy etc) Initial development may not be as fast as the other options, but if you'll need flexibility, this will end up being a much cleaner setup. I'd suggest you take a look at DOJO, and ExtGWT .
Cheers
Seref
It looks like XHTML + JavaScript could be enough for the dragging & dropping functionality you describe. This means you can use just about any web framework of your choice. If you need frequent asynchronous server calls (AJAX) then GWT is the most standard Java framework I think, although it has its peculiarities. Personally I like Wicket because it does not use XML configurations, relies heavily on code and has a nice community around it. Wicket also offers good AJAX support btw.
I work in a medium to small team ( 10 people ) developing and supporting several web enterprise applications.
We have a dozen of them built with a house-made framework with asp-classic working against ms-sql server.
We are evaluating the migration to a new development stack.
We'd like it to be open (free) and simple.
I've been looking around the java web frameworks, but all of them seem to be extremely overbloated for our needs (with the possible exception of http://www.playframework.org/, which I couldn't study yet...)
We are thinking about porting our own framework to this new stack, rather than adopting a whole new stack that we are unaware of ...
so far now, we though about the following possibilities
plain java - jsp - jsf
groovy - gsp (no grails at all)
jruby (no rails at all)
we feel really comfortable working with dynamic languages (well, as dynamic as classic asp can be) and with a lean and understandable framework...
I see no small and simple web frameworks for java, like there are for php or ruby...
I really like groovy, but I see no web implementations outside of grails... Besides the language documentation doesn't seem to be quite complete (I might be looking in the wrong place, perhaps)
php could be an option, but I think it would be hard to advocate for it in my current work...
any other option, advice, pros and cons?
thanks a lot
--
edit
some related link Can anyone recommend a simple Java web-app framework?
I'd suggest you take another look at Grails. It does use hibernate and spring under the covers, but for most situations, you don't need to know the details of those frameworks. There's a large community and lots of documentation/blogs/mailing lists for support, as well as a thriving plugin community with over 300 plugins solving pretty much any need.
If you're still put off by grails, you could look into the play framework. I don't have any experience with it, but there has been some traffic recently around it on hacker news and the like. I know it uses groovy for the templating language.
I cannot recommend anything, but strongly recommend that you consider these things:
Rapid development. Basically you want to save a page file, and reload it in the browser. Instantly! It can be done, do not settle for long deployment times.
Plain, readable text files!
Convention coding instead of explicit coding - big XML files will eventually drive one or more developers insane. The less, the better.
Good tool support (just having syntax coloring may be a big help)
Consider the long term support of your choice. You are basically remarrying with your software - will it still be maintained in 10 years? By whom? Will you have alternatives (JSR's are great - look at the amount of servlet engines)?
And WHEN you choose - get the source code for it, and ensure that it builds correctly. It will never be easier than now, and some day you WILL need to fix something inside. On short notice! (You may even consider allocating resources for donating documentation/patches/time to the open source project you are building your business on).
EDIT: A few more things:
You want to be able to verify things at compile time. One of the things that make it possible to build cathedrals in Java is that the static typechecking prevents a lot of nasty runtime errors. "Oh, THAT method? Well, it's not here, sorry. Boom!"
You want good error reporting. Built in! Try throwing a NullPointerException deep, deep down and see what 1) the user and 2) the developer is told about it. Anything that requires going to a log file to get the details WILL cause calls at 3 AM eventually.
Look into scalability from the start. Any non-trivial customer will need to and the world goes to multicores, so you might as well think about it already now. What will you do when all the magic pixie performance dust has been used and it just isn't enough: The application requires more than a single box.
And read this: http://www.pragprog.com/titles/mnee/release-it
You're forgetting about the other major player in this field: the LAMP stack (linux, Apache, MySQL and mod_perl). All components are free, there are many books available on LAMP development and each of these components, and there are vast numbers of libraries and components already available.
Apache: the Definitive Guide
Learning Perl: by SO's brian d foy
Practical mod_perl
If you are afraid of Grails and need Java, try Stripes and read the excellent Stripes book (http://www.stripesbook.com/blog/). You can buy the eBook pdf for $23. The book covers the framework in amazing detail. Stripes is a very strong, lightweight MVC framework that deals with all the common problems of web development (templates, url mapping, form validation, security, internationalization, testing) but it won't automagically create the database layer for you unless you want it to by using Stripernate. You can also use Groovy with it. You can use it standalone or with Spring.
I've had great success in simple web projects using Spring MVC with JSTL JSPs. Spring MVC is a framework that can be kept pretty darn simple (1 additional XML file used for configuration). You can eschew all the fancy options and just specify a set of JSPs that you want to associate with view names, then forward to those views by specifying their names in the controller.
Spring MVC can also easily scale up and be as complex as you need, letting you switch from JSTL to JSTL with Tiles, or Struts, or JSF, or Wicket. It can also handle complex web flows using the Spring Web Flow project. But for most projects I just keep it simple -- build a JSTL JSP, create a controller that provides the objects that JSP needs, and associate them by having the controller return that view. Once you get the project set up and you're familiar with the configuration, it takes maybe a couple minutes to wire a new page into place.
If you like Groovy but don't like Grails you could try Gaelyk, which is a lightweight Groovy framework. However, AFAIK you can only use Gaelyk if you're hosting the app on the Google App Engine
If your apps won't be hosted on GAE, and you really don't want to use Grails, another option is to use Groovlets, Groovy template servlet, GSPs.
However, personally I think it's a big mistake to dismiss Grails. It really is a great framework, and you can go a long way without knowing much about Spring and Hibernate. One of your complaints is a lack of Grails documentation. I think you must have been looking in the wrong place, because in addition to all the books available, there's a very extensive reference document and a lot of other documentation available on the website. Finally, there's a very active mailing list.
My platform of choice is JRuby - Rails (3) because of its very rich and powerful ecosystem, but mainly because:
* very easy to use
* many MANY libraries
* fast support via IRC
* deep documentation
You can also check out Scala + Lift Web Framework ( imho best static typed language, nice framework )
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I'm at the beginning/middle of a project that we chose to implement using GWT. Has anyone encountered any major pitfalls in using GWT (and GWT-EXT) that were unable to be overcome? How about from a performance perspective?
A couple things that we've seen/heard already include:
Google not being able to index content
CSS and styling in general seems to be a bit flaky
Looking for any additional feedback on these items as well. Thanks!
I'll start by saying that I'm a massive GWT fan, but yes there are many pitfalls, but most if not all we were able to overcome:
Problem: Long compile times, as your project grows so does the amount of time it takes to compile it. I've heard of reports of 20 minute compiles, but mine are on average about 1 minute.
Solution: Split your code into separate modules, and tell ant to only build it when it's changed. Also while developing, you can massively speed up compile times by only building for one browser. You can do this by putting this into your .gwt.xml file:
<set-property name="user.agent" value="gecko1_8" />
Where gecko1_8 is Firefox 2+, ie6 is IE, etc.
Problem: Hosted mode is very slow (on OS X at least) and does not come close to matching the 'live' changes you get when you edit things like JSPs or Rails pages and hit refresh in your browser.
Solution: You can give the hosted mode more memory (I generally got for 512M) but it's still slow, I've found once you get good enough with GWT you stop using this. You make a large chunk of changes, then compile for just one browser (generally 20s worth of compile) and then just hit refresh in your browser.
Update: With GWT 2.0+ this is no longer an issue, because you use the new 'Development Mode'. It basically means you can run code directly in your browser of choice, so no loss of speed, plus you can firebug/inspect it, etc.
http://code.google.com/p/google-web-toolkit/wiki/UsingOOPHM
Problem: GWT code is java, and has a different mentality to laying out a HTML page, which makes taking a HTML design and turning it into GWT harder
Solution: Again you get used to this, but unfortunately converting a HTML design to a GWT design is always going to be slower than doing something like converting a HTML design to a JSP page.
Problem: GWT takes a bit of getting your head around, and is not yet mainstream. Meaning that most developers that join your team or maintain your code will have to learn it from scratch
Solution: It remains to be seen if GWT will take off, but if you're a company in control of who you hire, then you can always choose people that either know GWT or want to learn it.
Problem: GWT is a sledgehammer compared to something like jquery or just plain javascript. It takes a lot more setup to get it happening than just including a JS file.
Solution: Use libraries like jquery for smaller, simple tasks that are suited to those. Use GWT when you want to build something truly complex in AJAX, or where you need to pass your data back and forth via the RPC mechanism.
Problem: Sometimes in order to populate your GWT page, you need to make a server call when the page first loads. It can be annoying for the user to sit there and watch a loading symbol while you fetch the data you need.
Solution: In the case of a JSP page, your page was already rendered by the server before becoming HTML, so you can actually make all your GWT calls then, and pre-load them onto the page, for an instant load. See here for details:
Speed up Page Loading by pre-serializing your GWT calls
I've never had any problems CSS styling my widgets, out of the box, custom or otherwise, so I don't know what you mean by that being a pitfall?
As for performance, I've always found that once compiled GWT code is fast, and AJAX calls are nearly always smaller than doing a whole page refresh, but that's not really unique to GWT, though the native RPC packets that you get if you use a JAVA back end are pretty compact.
We have been working with gwt for almost 2 years. We have learned a lot of lessons. Here is what we think:
Dont use third party widget libraries especially gwt-ext. It will kill your debugging, development and runtime performance. If you have questions about how this happens, contact me directly.
Use gwt to only fill in the dynamic parts of your apps. So if you have some complex user interactions with lots of fields. However, don't use the panels that come with it. Take your existing stock designer supplied pages. Carve out the areas that will contain the controls for your app. Attach these controls to the page within onModuleLoad(). This way you can use the standard pages from your designer and also do all the styling outside the gwt.
Don't build the entire app as one standard page that then dynamically builds all the pieces. If you do what I suggest in item 2, this won't happen anyway. If you build everything dynamically you will kill performance and consume huge amounts of memory for medium to large apps. Also, if you do what I am suggesting, the back button will work great, so will search engine indexing etc.
The other commenters also had some good suggestions. The rule of thumb i use is to create pages like you were doing a standard web page. Then carve out the pieces that need to be dynamic. Replace them with elements that have id's and then use RootPanel.get( id ).add( widget ) to fill those areas in.
Pitfalls that we've run into:
While you can get a lot of mileage from using something like GWT EXT, any time you use this sort of thin veneer on top of a JavaScript library, you lose the ability to debug. More than once I've bashed my head on the desk because I cannot inspect (inside my IntelliJ debugger) what's happening in the GWT EXT table class... All you can see is that it's a JavaScriptObject. This makes it quite difficult to figure out what's gone wrong...
Not having someone on your team who knows CSS. From my experience, it didn't matter that the person wasn't expert...it's enough that he has some good working knowledge, and knows the right terms to google when necessary.
Debugging across browsers. Keep an eye on Out of Process Hosted Mode[1][2][3], hopefully coming in GWT 1.6... For now, you just have to get things good with hosted mode, then use the "Compile/Browse" button, where you can play with other browsers. For me, working on Windows, this means I can view my work in FireFox, and use FireBug to help tweak and make things better.
IE6. It's amazing how different IE 6 will render things. I've taken the approach of applying a style to the outermost "viewport" according to the browser so that I can have CSS rules like:
.my-style { /* stuff that works most everywhere */ }
.msie6 .my-style { /* "override" so that styles work on IE 6 */ }
Finally, make sure you use an editor that helps you. I use IntelliJ -- it's got lots of GWT smarts. E.g., If I try to use a class that isn't handled by the JRE emulation, it lets me know; if I specify a style for a widget, and I haven't defined that style yet, the code gets the little red squiggly... Or, when looking at the CSS, it will tell me when I've specified conflicting attributes in a single rule. (I haven't tried it yet, but I understand that version 8 has even better GWT support, like keeping the "local" and "async" RPC interfaces and implementations in sync.)
GWT 2.0, which is supposed to come out sometime in the next few months, solves a lot of the issues discussed.
Create layouts using an html/xml like syntax
Dynamic Script Loading - only the essential JS will be downloaded initially. The rest will be downloaded as needed
In-Browser Hosted Mode - This might take care of the hosted mode speed issues discussed, among other benefits
"Compiler Optimizations" - Faster compilation, hopefully
GWT 2.0 Preview Video at Google I/O
Not "unable to be overcome" but a bit of a pain for something basic.
Date handling:
GWT uses the deprecated java.util.Date which can lead to unexpected behaviour when dealing with dates on the client side. java.util.Calendar is not supported by GWT. More info here.
Related problem examples:
GWT java.util.Date serialization bug
Get Date details (day, month, year) in GWT
Client side time zone support in GWT
I'll add some points to the ones already mentioned:
Databinding/validation. GWT doesn't have a databinding/validation support out of the box, although there are some projects on this area starting to emerge. You'll find yourself writing alot of this:
TextField fname, faddress;
...
fname.setText(person.getName());
faddress.setText(person.getAddress());
...
Lazy loading. Since gwt is on the client side, lazy loading is really not an option. You'll have to design your RPCs and Domain Objects carefully in order to
send all your object data that is needed
avoid eager fetching all of your data
You'll have also to make sure that you will not send proxies/non serializable objects. hibernate4gwt can help you with these points.
UI design. It is harder to visualize an UI in java (Panels, Buttons, etc) than in html.
History support. GWT does not ship with a History subsystem, nor does it ship with any subsystem for nice urls or statefull bookmarking. You'll have to roll your own (although it has support for History tokens, which is a start). This happens with all AJAX toolkits AFAIK.
IMHO, GWT is missing a framework that has out of the box support for all of the issues mentioned on this 'thread'.
I'm working on a project right now that uses EXT GWT (GXT) not to be confused with GWT EXT. There is a difference, EXT GWT is the one that is actually produced by the company that wrote ExtJS the javascript library. GWT EXT is a GWT wrapper around the ExtJS library. GXT is native GWT.
Anyways, GXT is still somewhat immature and lacks a solid community that I feel GWT EXT has. However, the future is with GXT, as it's native GWT and actually developed by the company that made ExtJS. GWT EXT is somewhat crippled as the license changed on the ExtJS library, thus slowing the development of GWT EXT.
Overall, I think GWT/GXT is a good solution for developing a web application. I actually quite like hosted mode for development, it makes things quick and easy. You also get the benefit of being able to debug your code as well. Unit testings with JUnit is pretty solid as well. I haven't yet seen a great JavaScript unit testing framework that I felt was mature enough for testing an enterprise application.
For more information on GWT EXT:
http://gwt-ext.com/
For more information on EXT GWT (GXT):
http://extjs.com/products/gxt/
No major pitfalls that I haven't been able to overcome easily. Use hosted mode heavily.
As you are using GWT-ext you will almost never need to touch CSS yourself unless you want to tweak the out of the box look.
My recommendation is to use a GWT "native" widget over a library one where they are close in features.
Re search engine indexing: yes the site will not have navigable URLs normally (unless you are only adding widgets to elements of a regular web site). You can do history back/forward functionality though.
I used GWT and GWT-ext together on a project a while ago. I found the experience quite smooth as web development goes, but my advice would be this:
Don't mix GWT native widgets with EXT widgets. It's confusing as hell, since usually the names are the same (GWT.Button or GWText.Button?)
One thing that happened to me that really made the code more complex than I'd like, was that I wanted a Panel that was
a) dynamically updatable
b) cascadable
GWT native panels are dynamic, Ext panels are cascadable. Solution? A GWT.VerticalPanel wrapping a GWTExt Panel... Chaos. :)
But hey, it works. ;)
I second the comment from ykagano, the biggest disadvantage is losing the V in MVC. Although you can separate the true ui class from the rest of your client side code, you cannot easily use an HTML page generated by a graphic/web designer. This means you need a developer to translate HTML into java.
Get a wysiwyg ui editor, it will save you lots of time. I use GWTDesigner.
The biggest upside of GWT is being able to forget about cross browser issues. Its not 100% but takes almost all that pain away. Combined with the benefit of hosted mode debugging (as opposed to Firebug which is excellent but not the same as a java debugger) it gives the developer a huge advantage in generating complex ajax apps.
Oh and its fast at runtime, especially if you use a gzip filter.
Slightly off-topic, but the #gwt channel on irc is very helpful, in-case you have a persistent problem.
GWT is pretty straight-forward and intuitive.
Especially with the release of UIBinder to allow GWT widgets to be laid out in XML and then coded-behind in Java.
So if you have used other Ajax or Flash design tools, or Silverlight, etc, GWT is very easy to learn.
The major hurdle, if not pitfall, is GWT RPC. The very reason you wish to use GWT is because of GWT async RPC. Otherwise, why not just rely on css to format your page?
GWT RPC is that element that allows your server to refresh data on your server without having to refresh the page. This is an absolute requirement for pages such as stock performance monitoring (or the current national and public debt of the US or the number of unborn babies aborted worldwide by the second).
GWT RPC takes some effort to understand but given a few hours, it should come all clear.
Above that, after putting in some effort to learn GWT RPC, you finally discover that you cannot use JSPs as the service component for RPC, unless ... I have an 8 part (I think) series on my blog on how to use JSP as the GWT RPC servicer. However, since you had not asked for answers but just issues, I shall desist from advertising my blog.
So. I very much believe that the worst roadblocks/pitfalls to using GWT is finding out how to properly deploy GWT async RPC and how to enable it to use JSP servicers.
We've had a very hard time marrying our GWT codebase with HTML web templates that we got from a web designer (static HTML pages with specific div ids that we wanted GWT to manage). At least back when we used it, we couldn't get GWT to integrate with parts of our website that were not coded in GWT. We had it working eventually, but it was a big hack.
The Async interface you have to write for each service interface looks like something that could have been automatically generated by the GWT compiler.
Compile times become long for large projects
But for a large Javascript project it's the best choice
GWT 2.4 has fixed many of the aforementioned issues and a great widget library is just coming out of Beta (Ext GWT 3.0.4 a.k.a. GXT), which is written completely in GWT, not a wrapper of a JS lib.
Remaining pain:
Lack of CSS3 selector support, you can use "literal()" in some cases to get around it.
Lack of support for CSS3 and modern browser events like transitionEnd.
Lack of Java Calendar class support (many years later).
Lack of JUnit4 support (5 years and counting).
Lack of clear road map and release schedule from Google GWT team.
Regarding GWT 2.4, Use Firefox when debugging GWT, it alot more faster then using chrome.
And if you'll using only firefox, consider putting this line in your project.gwt.xml file
<set-property name="user.agent" value="gecko1_8" />
Also, If you're using eclipse, then add the following under arguments -> VM arguments:
-Xmx512m -XX:MaxPermSize=1024m -XX:PermSize=1024m
You can divide your server and client, and use the following under arguments -> Program arguments:
-codeServerPort 9997 -startupUrl http://yourserver/project -noserver
Also, to prevent refreshing your server on each change, use JRebel
http://zeroturnaround.com/blog/how-to-rock-out-with-jrebel-and-google-web-toolkit-gwt/
And here's a live demo
http://www.youtube.com/watch?feature=player_embedded&v=4JGGFCzspaY
One major pitfall is that sometimes you need to explicitly assign an id to what ultimately becomes an HTML element to be able to use certain CSS styles. For instance: a GWT TabPanel will only do :hover over tabBarItems when the tabBar of the tabPanel has been assigned an id and you specify a :hover on that elementId.
I wrote about some other disadvantages of GWT elsewhere, but they are already covered by rustyshelfs answer :).
I have done a lot of work on GWT recently, and this is wht i have to say:
CSS styling is tricky only sometimes, use IE developer tool in IE and firebug in Firefox to figure out what exactly is happening and you will get a clear idea of what css needs to be changed
You can use tricks to get google to index it. A very famous site is http://examples.roughian.com/ check its ratings at google. A far less famous site is www.salvin.in (couldnt resist to mention that), i optimised it to words: salvin home page (search google for these three words)
I do not know much about GWT-EXT, But i too am of the belief that there is no need to include Third party libraries.
Best of luck on your decision :)
GWT does Browser Sniffing instead of Feature Detection and your application will not work on some browsers (specially new ones)
Here are some references of the problem:
google-web-toolkit Issue 2938: RFE: improve the user.agent property-provider to cope for userAgent string "masking"
Iceweasel no longer supported? - Google Docs Help
GWT implementations for every browser
Here are some references to Feature Detection:
Browser Detecting (and what to do Instead)
Feature Detection: State of the Art Browser Scripting
Browser Feature Detection
Extracted from Comparison of JavaScript frameworks - Wikipedia
The GWT team make a lot of great improvements in to last year releasing GWT 2.7. One major weakness of GWT was that compilation takes to much time in GWT 2.6 and below. This is now gone GWT has not incremental compile which is super fast and compiles only the changes.
GWT 2.7 now has (Source):
Incremental builds now just seconds
More compact, more accurate SourceMaps
GSS support
JSInterop
Great JavaScript Performance
Smaller Code Size
The best way to get reliable facts are from the gwt survey. One of the biggest issues with GWT has always been a long compile time. Fortunately, it's improving very quickly so it won't be a significant issue in the near future. Another pitfall is that GWT is dramatically more complicated because Java is a more complicated language that resists bad coders every step of the way. In addition, compiling adds a layer. For example, js interop requires a little boilerplate. The fundamental issue is that GWT wasn't designed to be simple. It was designed from the ground up for extremely complicated web apps and the entire community consistently prioritizes, performance, code quality, architecture etcetera over easy coding.
Remember that you can use js in GWT at any point so if you are struggling with GWT consider using js. At the end of the day GWT is js so you can do anything in GWT that you can in js. In fact, most GWT projects use js. The problem is that GWT is drastically more complicated. Nevertheless, it's sometimes worth the extra complexity.
It's worth noting that GWT 3.0 will bring massive improvements.
Re-using RPC service objects.
It causes race conditions with symptoms that look like the app hanging.
Pitfalls I ran into
1. Different behaviour in superdev mode. E.g. Someclass.class.getName() works absolutely fine in Superdev mode and returns the fully qualified name of the class. In productive mode this does not work.
addWidget(widget) will call widget's removefromparent()
GWT is a technology masterpiece. It unites client and server programming making it one coherent application - the way software was written before "layering", and the way it should be written. It eliminates different skills sets, miscommunication between team members, and generally the whole Web Design phase: both the artistic and programming. And it is the closest you'd get to mobile e.g. Android development. In fact GWT was designed to generate different native UIs, not just HTML. Though it requires enormous discipline to ensure such decoupling - to keep your inner layers presentation-agnostic.
The first mistake you should avoid, which took me four years to realize, is using third-party extensions like EXT-GWT aka GXT and SmartGWT. It is very tempting to start using their pretty desktopish widgets instead of investing in your own styling, but I cannot tell how many problems I had with SmartGWT until I finally got fed up. In short it freezes the core GWT feature set at the certain (pretty outdated) level and then builds on top of it. Also keep in mind, that chiseled desktop look and feel looks silly nowadays, not to mention the sluggish performance, tons of bugs, and compatibility features - especially on mobile devices. You want to stay as close to the native browser controls, as possible i.e. dropdowns rendered as native <select> elements, not some custom-painted controls.
Thanks to mobile trends the whole UX is becoming simpler and flatter, so you don't need to do much to style a sharp-looking application. Though if you want "3D" look, there are also gradients. CSS3 made everything easy, and GWT wraps it an elegant object-oriented manner unlike the raw CSS. So don't be discouraged by looking at rather ugly barebones controls in the GWT Showcase. The GWT team intentionally didn't offer any styling, because it it the developer's job.
The rest is pretty much conventional browser programming in strongly typed Java with beautiful concise APIs. But of course never forgetting your code runs inside the browser, so all of the calls are asynchronous e.g. you cannot call GWT-RPC methods in a loop (to populate some list), but need to recursively chain them if you ever come to to this situation.
There are some self-proclaimed "anti-patterns" like don't use GWT-RPC. It's been good to me so far: for 10 years. Simplicity is key. I wouldn't think even a second to sacrifice some marginal performance for code elegance and maintainability. besides this is not where your bottlenecks would be - in the database. Of course mind how much data you are sending to the client.
And if you cannot find or style the existing gadget - read rich HTML5 element set, you can always wrap a third-party one. I did it with a popular jQuery FullCalendar. Not rocket science at all. Everything else like Google Maps and Google Charts has semi-official GWT wrappers.
GWT is perfect. The only reason it doesn't get enough love is because early Internet adopters who still influence the industry didn't come from Computer Science and object-oriented languages to appreciate them. They have either artistic (Photoshop/WordPress) or network (Perl/Python) background.