Google Web Toolkit (GWT) Overview

Posted in: GWT

 The Google Web Toolkit (GWT) is a toolkit to develop Ajax web application with Java. The programmer writes Java code and this code is translated into HTML and Javascript via the GWT compiler.
The compiler creates browser specific HTML and JavaScript to support all the major browsers correctly. GWT supports a standard set of UI widgets, has build in support for the browser back button and a JUnit based test framework.
GWT provides two modes

• Development Mode: allows to debug the Java code of your application directly via the standard Java debugger.
  
• Web mode: the application is translated into HTML and Javascript code and can be deployed to a webserver.
  

 Modules, Entry Points and HTML pages

GWT applications are described as modules. A module "modulename" is described by a configuration file "modulename.gwt.xml". Each module can define one or more Entry point classes. An entry point is the starting point for a GWT application, similar to the main method in a standard Java program. A Java class which is an entry point must implement the interface "com.google.gwt.core.client.EntryPoint" which defines the method onModuleLoad().
The module is connected to a HTML page, which is called "host page". The code for a GWT web application executes within this HTML document.
The HTML page can define "div" containers to which the GWT application can assign UI components or the GWT UI components are simply assigned to the body tag of the HTML page.

Using CSS

The look and feel of a GWT application can be customized via CSS files. Each widget in GWT can be given a HTML "div" container and can therefore be individually styled by CSS. You use the Java method setStyle(String s) for this.