Milen Dyankov's blog

Imagine you are not a Java guru but a ... connoisseur of art. You are visiting a beautiful city called Liferay and you know it's full of museums, art galleries, music halls, great architecture, ... You can certainly organize your trip in many different ways. One of them is taking the bus tour and this is what a Liferay Portal Systems Development book would be in this analogy. Actually it may even be a very good idea for a start. However, please note, the route is somewhat outdated and passes by places which no longer exists. Also the tour guide is all the time pointing out things, but as soon as the story becomes really interesting and you can't wait for the details, she moves to the next subject.

Here I go again. This time reviewing the "Liferay Portal systems Development" book. No, I'm not preparing to apply for book reviewer position at Packt Publishing. And yes, I'm a bit worried this blog is recently more about books and less about technology. So once I'm done reading this one, I'll try to concentrate on some more technical posts and give the books some rest (unless I finally find the strength to write one).

As I promised a few weeks ago, in this post I'll share my thoughts about "Liferay Beginner's Guide" book. As with earlier reviews, don't expect any judgments, recommendations or generalizations. Those are to be made by you. I'll only concentrate on what I found interesting (or boring) and worth mentioning (for one reason or another). So let me try to summarize over 350 pages in a few lines.

If you are following any Liferay related sites, forums, tweets, ..., then for sure you've heard about the new book titled "Liferay Beginner's Guide". The book was released in December 2011 and it is getting a lot more attention that I would ever expect. To be honest I'm kind of surprised there are so many Liferay beginners out there. So I volunteered to review the book hoping to check for myself whether all this buzz is only the result of good marketing strategy or it really provides the beginners with the answers they need.

After my "Pluggable mobile device detection" presentation during Liferay Europe Symposium a lot of people asked about the mobile device emulator I was using. The truth is, it's not a real "emulator" but a simple combination of html page and a Firefox user script. However, it does the trick and for most people seems to be good enough (at least for a start). So, I made a promise to share it and finally found the time to blog about it.

One of the problems with GWT (which is even more noticeable in portal environment) is preserving it's state between page reloads. In a GWT-only application (or single portlet on the page case) one can give user no other option but using only GWT controls to practically avoid page reloads. In most cases however this is not really possible nor wise thing to do. In portlet environments in particular, reloading the page is a very commmon thing to do, giving all portlets a chance to refresh their content after some action has taken place. The thing is, GWT portlets will, by default, render their initial state, which may not be what user expects.      

For example, consider the GWT Chatroom portlet I was using in my previous posts Liferay GWT portlet - how to make it "instanceable" and use GWT RPC and Liferay GWT portlet - replacing GWT-RPC with JSON. Imagine user has entered a chatroom. Then she clicks on some other portlet on the page. The page is reloaded and Chatroom portlet returns to it's initial state. The user will have to enter the room again every time she clicks on another portlet. Let's see how this can be fixed.

This is a continuation of my previous post Liferay GWT portlet - how to make it "instanceable" and use GWT RPC. The approach described there uses Liferay specific functionality called  PortalDelegateServlet. This way one can easily use GWT RPC which somewhat simplifies client-server communication. However if you need to develop a JSR 286 portlet you need a more standard compatible way of doing AJAX calls. For this reason JSR 286 defines serverResource method and this post will show how to refactor the code to replace GWT RPC calls with exchanging JSON messages using serverResource method.

  Almost every portal related RFI/RFP my company has received in the last couple of years contained some requirements about mobile version. Fortunately the times when every device had it's own idea of how web content should be served are gone. Nowdays we can afford to pretty much ignore WML, C-HTML, ... as almost any modern device understands at least XHTML Mobile Profile. However this does not always mean there can be one mobile version for all. Here are some typical requirements:

• make a dedicated version for iPhone (imitate iPhone interface to make it look like native application)
• allow to switch between mobile and desktop version if device is smartphone
• provide alternative input methods if device does not have QWERTY keyboard
• design dedicated version for tablets

I have spent some time thinking about how to address this issues with Liferay Portal. Having some experience with WURFL, Volantice and designing web applications for mobile devices in general, I thought it would be great if I could dynamically change Liferay's look and feel based on device capabilities. And this is how Liferay multi-device extension was born.  

Every once in a while somebody asks about writing Liferay portlets in GWT. It seems a lot of people are successfully using GWT with Liferay but surprisingly I couldn't find any complete tutorial on the subject. There are a of course tutorials explaining the basics but what they concentrate on, is how to build single-instance and client-side-only portlets. This is good enough to get you started but chances are sooner or later you'll need to place two instances of the same GWT portlet on the same page and/or implement GWT RPC to make use of the Liferay services.

I've reached that point myself sometime ago and unfortunately had to solve the problem myself. Then I wrote sample portlet called gwt-chatrooms-portlet to demonstrate the solution and hopefully save you some time. So here is a step by step tutorial how to create GWT portlet for Liferay 6.0.5 which:

• allows many instances to be placed on the same page
• uses GWT RPC for client-server communication

The last 6 months were extremely busy for me.  A lot had happened in both private and professional aspects. Having that in mind I'm quite happy I manged to deal with completely new experience - being a technical reviewer of "Liferay User Interface Development" - a new book published recently by Packt Publishing. Despite the lack of spare time I was somehow able to read and comment on drafts of 10 chapters covering things like theme development, layout templates, velocity templates, tag libraries, AlloyUI, and much more. Hopefully my comments and opinions ware useful for the authors and help them improve the book.