Getting Started with GWT: Your First Application

A step-by-step guide to creating your first Google Web Toolkit (GWT) application.

1. Setting Up Your First GWT Project

To start with GWT, you'll need the following:

• Java Development Kit (JDK) installed on your system.
• An IDE like IntelliJ IDEA or Eclipse with GWT plugins.
• The GWT SDK, which you can download from the official GWT website.

Once you have the prerequisites, follow these steps: Quick Setup: Installing GWT and Setting Up Your First Project

2. Understanding the Project Structure

A GWT project has three main parts:

• Client: Contains the application code written in Java, which is later compiled into JavaScript.
• Server: Houses server-side logic, such as servlets and RPC endpoints.
• Public: Stores static resources like HTML, CSS, and images that are served to the browser.

After generating a project, you'll notice a default module configuration file with the extension .gwt.xml. This file defines the module's entry point and other settings.

3. Writing and Running a "Hello, World!" Application

Let’s create a simple "Hello, World!" application:

1. Open the client package and locate the main entry-point class, typically named MyApp.java.
2. Replace the default content with the following code:

   package com.example.myapp.client;
   
   import com.google.gwt.core.client.EntryPoint;
   import com.google.gwt.user.client.ui.Label;
   import com.google.gwt.user.client.ui.RootPanel;
   
   public class MyApp implements EntryPoint {
       public void onModuleLoad() {
           Label helloLabel = new Label("Hello, World!");
           RootPanel.get().add(helloLabel);
       }
   }

3. Start the GWT Development Mode and launch your application in a browser. You should see "Hello, World!" displayed.

4. Introduction to GWT DevMode

GWT Development Mode (DevMode) is an essential tool for testing your application:

• It allows you to debug your application in Java before compiling it into JavaScript.
• To start DevMode, run the appropriate command or configuration in your IDE. Typically, this involves launching the DevMode class with your project module as an argument.
• Open the provided URL in your browser to access the hosted mode environment.

DevMode significantly speeds up development by enabling live debugging and instant feedback.