CSC/ECE 517 Fall 2014/ch1a 6 bn

Google Web Toolkit

Google Web Toolkit(GWT) is a set of tools used to develop browser based RICH Web Applications(RIA). It is a free open source web framework released in 2006 under Apache 2.0 License. The focus of this toolkit is to provide great user experience by bringing the features and feel similar to that of a desktop application to the browser based web applications. GWT as a framework can be used to build large scale and high performance easy-to-maintain web appliations. GWT is used by many products at Google, including AdWords, AdSense, Flights, Hotel Finder, Offers, Wallet, Blogger, Maps.

The latest Version of GWT (GWT 2.6.1) was released on May 10, 2014.

Contents of the Toolkit

The Toolkit consists of a software development kit (GWT SDK) and an eclipse Plugin (Plugin for Eclipse).

GWT SDK

GWT SDK contains the Java API libraries, compiler, and development server. It lets you write client-side applications in Java and deploy them as JavaScript. The three major components of the SDK are:

GWT Java to JavaScript compiler

This is the most important part of GWT which makes it a powerful tool for building RIAs. The GWT compiler is used to translate all the application code written in Java into JavaScript.It also supports mixing of Java code with existing JavaScript code using JavaScript Native Interface (JSNI), which allows embedding of JavaScript code within Java classes in order to facilitate Java-to-JavaScript communication. An example of embedded javascript in java is shown below.

private native void nativeMethod()
/*-{
     $wnd.jsFunction = function(x) {
       alert(x);
     };
     alert("hello");
}-*/;

One key feature of the GWT compiler is that it generates multiple output JavaScript files from the input code, one per each browser to ensure cross browser compatibility of the application. The browsers currently supported by the compiler include

Firefox

Internet Explorer 8, 9, 10, 11

Safari 5, 6

Chromium and Google Chrome

Opera latest version

Compiler Modes

The compiler has three style modes that determine what the resulting Java-Script looks like. The default style is obfuscate, which makes the JavaScript look like alphabet soup. Everything is compressed and nearly impossible to decipher.An example of the obfuscated code is given below

function x(){return this.y + '#' + this.b();}

The second style is pretty which generates readable JavaScript as shown below.

function _toString(){
  return this._typeName + '#' + this._length();
}

The third style is detailed, which produces JavaScript code that looks like the pretty style with the addition of the full class name as part of the JavaScript method name. An Example would look like

function java_lang_Object_toString__(){
return this.java_lang_Object_typeName + '#' + this.length__();
}

Generally Obfuscate is used for production as it is the most optimized and compressed version of the output code and would result in faster pages. Using Obfuscate also provides a certain amount of security to the output code and can prevent code theft by making it difficult to read the output. Pretty and detailed modes are used mainly in development to aid in debugging.

JRE Emulation library

Google Web Toolkit includes a library that emulates a subset of the Java runtime library. The list includes java.lang, java.lang.annotation, java.math, java.io, java.sql, java.util and java.util.logging.

GWT UI building library

This part of GWT consists of many subparts which includes the actual UI components, RPC support, History management. GWT ships with a large set of widgets and panels for laying out UI.

Plugin for Eclipse

Plugin for Eclipse provides IDE support for GWT and App Engine web projects.