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Java, Scala, and everything

Monday, March 22, 2010

JavaScript training

This weekend I was able to take part in JavaScript training by Damian Wielgosik . As I was not very experienced JavaScript developer, I have learned a lot. I also got convinced that in JavaScript everything is possible :)

I am impressed by the trainer. I was quite surprised when I found out that it was the third training he conducted. I thought he is much more experienced. He had great "contact with the audience", atmosphere was very friendly, nobody was afraid to ask questions or discuss. Thank you Damian!

Two days full of training is quite a much time, so there was also place for exercises. This was very good, nothing consolidates knowledge like some exercises and because Damian was always there to help if we were stuck, we were not wasting time. Doing exercises in groups was also very good idea. We worked as a team and helped each other. I never doubted in efficiency of pair programming :)

Scope of topics was impressive. I learned a lot about prototypes and constructors, which was a bit strange for Java programmer (but not so much if he was also learning Ruby ;)) I think we covered pretty much everything in JS, from basics (which we run through quite fast) to optimization.

I would also like to thank other participants for great atmosphere, discussions, questions, help and info about "pierogarnia" :) I wish I could attend more such good trainings.

Friday, March 19, 2010

Review: Programming Scala, by Venkat Subramaniam

Programming Scala: Tackle Multi-Core Complexity on the Java Virtual Machine (Pragmatic Programmers)Courtesy of The Pragmatic Bookshelf I was able to read "Programming Scala" by Venkat Subramaniam. If you are a Java programmer, this book is a great introduction to Scala for you. It is packed with knowledge. There was not even one chapter after reading which I could say "well, this was quite obvious, I could expect this". Book is targeted for experienced Java programmers, so author does not cover things we already know. This was great for me, my time was not wasted learning what I don't need. Instead, I was led from easier topics in Scala (like classes, typing, closures) to more difficult ones (pattern matching, actors and concurrency) at a nice pace. Most topics are explained quite clearly and understandable. There are few which I had difficulties understanding and I needed to fiddle with some code to get it. But fiddling with code is fun for programmer, isn't it? One of such topics were actors, which is a great feature in Scala and something completely new for Java programmer (unless he knows Erlang too ;)). It took me some time with IDE to understand actors, but it was also fun.

The book not only teaches how to program in Scala, but also shows tools to run these programs. Knowing that Scala doesn't necessarly need to be compiled to run and that it can be run as a script can be very useful if you need to do some simple job on your system. Author shows how to use it as a scripting language. I also liked the last chapter in which author creates Scala application using various features covered in the book. It was a good way to sum up.

The only weak point of this book are examples. Especially at the end of the book they become more and more difficult and not always clearly explained. Another disadvantage of examples is their little connection with reality. Have you ever need to count letters in blog URL? In some cases they even show bad practice like throwing general Exception. I know it's only example, but educational book should not promote bad practice even there.

Said all this, I would recommend this book to every Java programmer who wants to learn Scala. If you are not afraid to fiddle a little with code (and you should not be, you are a programmer after all;) ) it is a very good book for you and you are it's perfect target.

Last but not least, not only author, but also editors deserve praise. I have PDF edition and I can login on pragprog.com page anytime and download it. I don't have to worry that if I loose it - it's lost for good. Moreover there are .mobi and .epub formats available. I could read the book on my phone on a bus or a tram which was very convenient. And there is even more - the books are DRM free, which shows publishers not only care for readers comfort, but also trust us. I appreciate that.

Tuesday, March 2, 2010

Simple AJAX with JSF 2.0

In JSF 2.0, there are tags added to make AJAX calls easy. Without further ado:

<?xml version='1.0' encoding='UTF-8' ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
 xmlns:ui="http://java.sun.com/jsf/facelets"
 xmlns:h="http://java.sun.com/jsf/html"
 xmlns:f="http://java.sun.com/jsf/core">
<h:head>
   <h:outputScript name="jsf.js" library="javax.faces" target="body"></h:outputScript>
   <title>Ajax</title>
</h:head>
<h:body>
   <f:view contentType="text/html; charset=UTF-8">
       <h1>Hello Ajax World!</h1>
       <h:form id="form">
           <h:inputText id="name" value="#{nameMBean.name}"/>

           <h:commandButton value="Reverse name via Ajax!">
               <f:ajax execute="name" render="reverseName"/>
           </h:commandButton>
           <h:outputText id="reverseName" value="#{nameMBean.reverseName}"/>
       </h:form>
   </f:view>
</h:body>
</html>

First things first. To use AJAX in JSF 2.0, we have to attach jsf.js file (line 8). Then we are ready.

Most interesting is line 18. <f:ajax> added to command button makes AJAX action fire when button is pressed. We could as well put it into <h:inputText> element, then it would fire on change of text inside (onchange event).

Parameter execute tells JSF which parts it should send to server for model update. This could be also form, for all the parameters in the form, or list of element ids separated by space. Parameter render denotes which parts of view should be rerendered after receiving AJAX response. Here we can also put more than one.

We can put more parameters to <f:ajax>, like event, where we can specify on which event AJAX action should occur (not necessarly click event), or listener, where we can call some method on managed bean.