GWT Java AJAX Programming

simon_kehler writes "The Google Web Toolkit (GWT) is a Java AJAX framework that provides an easy to use programming paradigm for web developers using the Java programming language. It is one of the more recent entrants into this field, but has been gaining a lot of traction and popularity. GWT Java AJAX Programming authored by Prabhakar Chaganti and published by Packt Publishing addresses the use of GWT to build ajaxified user interfaces. The author gently introduces the reader to GWT and then leads the reader through a series of tasks, each of which shows how to perform an useful action with GWT." Read below for Simon's review.

GWT Java AJAX Programming
author	Prabhakar
pages	240
publisher	Packt Publishing
rating	8
reviewer	simon Kehle
ISBN	1847191002
summary	A great book for learning the different facets and features of GWT

I am a software architect working for a startup that is evaluating the use of GWT for a new project. I lead a team of experienced Java developers that are comfortable working with Swing and have reasonable familiarity with Struts. We have looked on with envy at all the nice things you could do with the AJAX integration built into web frameworks in languages such as PHP and Ruby. When I came across GWT we decided to take it for a spin and see if your team would be comfortable using it. The documentation that comes with the GWT download is a bit sparse. I was looking for a more in depth intro to the framework and came across this book. this seems to be the first print book on the GWT framework.

The book is divided into ten chapters. An introduction to GWT and its download and setup is provided in the first chapter. The author then shows how to create random quote GWT application in chapter 2. This is a nice example that immediately gives you the flavor of what its like to work with GWT. It shows you the steps involved in writing and running a simple GWT app. Chapter 3 details the service interfaces that you need to create as a part of any GWT application. These are the heart of how the AJAX mechanism works in this framework. Chapters 4-6 go through a lot of tasks that show you how to create increasingly complex user interfaces using the GWT framework. Chapter 7 deals with creating custom widgets that can be shared across applications. Unit testing for GWT applications is covered in chapter 8 (Yes, you can unit test your AJAX apps!). I18N and client XML support are dealt with in chapter 9 and finally chapter 10 shows how to deploy your applications.

This book moves along at a fairly rapid pace and is a quick read. The examples chosen for the tasks are well thought out and show different features in GWT. There are several really cool and innovative examples in this book: Password strength checker, uses colored check boxes to visually show the strength of a password. A very different way of using a check box. Dynamic Lists, change list entries as selections change. Flickr label, recreates the cool label widget that was made famous by Flickr. Sticky Notes, you create post it notes in your browser and drag them around to place them as you want (uses GWT drag support.) Mona Lisa jigsaw puzzle, rearrange Mona Lisa (uses GWT drag support.) Moo.fx, uses moo.fx javascript library for effects (uses JSNI.) Color Selector, integrates Rico Javascript library into GWT (uses JSNI.) Calendar, a very cool mac os x like calendar widget (Creates a compound widget.) Weather, another widget (creates a compound widget.) I18N, displays the country flag based on the locale (uses i18n support.)

I had played around a bit with GWT before. So some of the things in the book were not new to me, but there were several things that I found very useful. GWT provides a way to integrate Java and Javascript (you can call into Java from JS or from JS to Java) called JSNI (Javascript Native interface). The JSNI examples in this book showed how to integrate with moo.fx, Rico and scriptaculous libraries. This was great as we have some homegrown Javascript libs that we would like to continue to use even when we move to GWT. If we can try to hook those in and call them from GWT, that would be sweet! The ability to create widgets that can be shared across applications is very important to our project. The author creates two widgets in chapter 7 — calendar and weather. Both of these were very cool and reminded me of my mac desktop widgets! The weather widget uses Yahoo's weather service to retrieve the information that is displayed. Again, very nicely done. The ability to unit test is another thing that is crucial for us. GWT leverages and extends JUnit to provide this support. However, this is one of the parts of GWT that people do not seem to be using much. Searching on the GWT forums reveals as much confusion about this topic. This book contains a chapter that shows how to unit test a GWT application. The examples are quite simple, but the creation of test suites was a good one, as I had struggled with that before. I really liked the author's coverage of deployment. He first shows how to manually deploy a GWT application. this gives you a feel for whats involved and what's going where. Then he automates that using ant and finally shows how to deploy from within eclipse. This is very useful as I have tripped over deployment before.

Overall, this is a well written book that was very useful to our team. There were a few examples that we had implemented differently than the author — table sorting, paging and in place editing of the tree nodes. I18N is a big topic and the author covers only one way to use it. It would have been nice to have a complete chapter devoted to that topic, as this is a topic of particular interest to us as we work with a multitude of languages. This is a very developer oriented book and assumes that you know Java, HTML, some Javascript and some CSS. Of course if you did not know those topics, you probably wouldn't be too interested in GWT! This is not a book that dives into the internals of how GWT works or tries to impress you with all the nitty gritty of the GWT architecture. The author provides you with ways in which you can accomplish most common tasks that require GWT. They may not be the only way to do things using GWT but it gets you comfortable using GWT and thinking about how you would actually apply it for your problem. I really enjoyed reading this book and its focus on the practical side of using GWT.

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All of these frameworks are mostly overkill

[roman_mir]

There is nothing that can't be done with a few lines of very simple javascript, here is a simple synchronized xml request test page that loads a simple data file and evaluates data quickly into an array and a map.

Test code:

<HTML><SCRIPT LANGUAGE="JAVASCRIPT"><!--
function handleHTTPResponseForArray(str) {
// UNPARSED TEXT EXAMPLE
handleHTTPResponse(str);
// ARRAY EXAMPLE
var textarea = document.getElementById("textarea2");
var result="";
var array=eval(str);
var hashMap=new Array(array.length);
for(var i=0;i<array.length;i++) {
hashMap[array[i][0]] = array[i][1];
result += "key:" + array[i][0];
result += "\t\t\tval:" + array[i][1] + "\n";
}
textarea.value=result;
// HASH MAP EXAMPLE
result="";
for(var i=0;i<array.length;i++) {
var tmpKey = array[i][0];
result += "key(" + tmpKey + ")=" + hashMap[tmpKey] + "\n";
}
textarea = document.getElementById("textarea3");
textarea.value = "Use result as a hash map with key/value pairs:\n";
textarea.value += result;
}
function handleHTTPResponse(str) {
var textarea = document.getElementById("textarea1");
textarea.value=str;
}
function handleHTTPError(str) {
alert(str);
}
function makeHTTPRequest(url, onLoadFunc, onErrorFunc) {
var request;
if(window.XMLHttpRequest) {
try {
request = new XMLHttpRequest();
} catch(e) {
alert(e);
return;
}
} else if(window.ActiveXObject) {
try {
request = new ActiveXObject("Msxml2.XMLHTTP");
} catch(e) {
try {
request = new ActiveXObject("Microsoft.XMLHTTP");
} catch(e1) {
alert(e1);
return;
}
}
}
try {
window.status = "ECSM:AJAX:Connecting to "+ url;
request.open("POST",url,false);
request.setRequestHeader('Content-Type','applicati on/x-www-form-urlencoded; charset=UTF-8');
request.send(null);
window.status = "";
} catch (e) {
window.status = "";
alert(e);
return;
}
if (request.status==200)
onLoadFunc(request.responseText);
else
onErrorFunc(request.status);
}
function testHTTPRequest() {makeHTTPRequest("mockups/load-data.txt", handleHTTPResponseForArray, handleHTTPError);}
//-->
</SCRIPT><BODY><input type="button" value="Run Test" onclick="javascript:testHTTPRequest();">
<table>< tr><td>Unparsed Text:</td><td><textarea id="textarea1" rows="10" cols="100" style="background

Re:All of these frameworks are mostly overkill

[Anonymous Coward]

There is nothing that can't be done with a few lines of very simple javascript, here is a simple synchronized xml request test page that loads a simple data file

You keep using that word. I do not think it means what you think it means.

(Especially after posting 75 lines of ugly Javascript.)

Re:All of these frameworks are mostly overkill

[roman_mir]

Ooh, goody gumdrops, /. never ceases to surprise me. Seriously, I wasn't going for Funny in the previous post.

For my next comedic number I will solve a quadratic equation.