Using GWT DevMode Tutorial

Welcome to the Using GWT DevMode tutorial. GWT DevMode is a powerful tool that allows you to run and debug GWT applications during development. With DevMode, you can test your application's functionality, monitor code changes, and efficiently diagnose and fix issues. This tutorial will guide you through the process of using GWT DevMode and provide examples to illustrate its usage.

Step 1: Launch GWT DevMode

The first step in using GWT DevMode is to launch it with your GWT application. You can do this by executing the following command in your project's directory:

$ java -classpath path/to/gwt-dev.jar com.google.gwt.dev.DevMode -war path/to/output -logLevel INFO your.module.EntryPoint
  

In this command, you need to specify the classpath to the gwt-dev.jar file, the output directory for the compiled GWT application, and the entry point module of your GWT application.

Step 2: Access the DevMode UI

Once GWT DevMode is launched, you can access the DevMode UI by opening a web browser and navigating to the following URL:

http://localhost:8888/YourModuleName.html?gwt.codesvr=127.0.0.1:9997
  

Replace YourModuleName with the name of your GWT module. The DevMode UI provides a user-friendly interface to interact with your GWT application and monitor its behavior.

Step 3: Debug and Test your Application

With GWT DevMode and the DevMode UI, you can now debug and test your GWT application. Here are some key features you can utilize:

• Code Reloading: Modify your Java code, and the changes will be automatically reflected in the running application without requiring a full recompile and restart.
• Remote Debugging: Attach a debugger, such as the browser developer tools, to the DevMode server and set breakpoints to step through your code and inspect variables.
• Interactive Mode: Enable Interactive Mode to display a development shell in the DevMode UI, allowing you to execute commands and interact with your application at runtime.

Common Mistakes

• Incorrectly specifying the classpath to the gwt-dev.jar file.
• Forgetting to update the DevMode URL with the correct module name and port number.
• Not utilizing the code reloading feature to see the effect of code changes immediately.
• Not leveraging the remote debugging capabilities to identify and fix issues efficiently.

Frequently Asked Questions

1. Q: Can I use GWT DevMode with IDEs?

   A: Yes, most popular IDEs, such as Eclipse and IntelliJ, provide integration with GWT DevMode for seamless debugging and development.

2. Q: How can I enable Super DevMode in GWT?

   A: Super DevMode is an enhanced version of GWT DevMode. You can enable Super DevMode by adding the -superDevMode flag when launching DevMode.

3. Q: Can I run GWT DevMode on a different port?

   A: Yes, you can specify a different port number by using the -port flag when launching GWT DevMode.

4. Q: How does code reloading work in GWT DevMode?

   A: Code reloading allows you to make changes to your Java code without restarting the application, making development more efficient and iterative.

5. Q: Is GWT DevMode suitable for production deployments?

   A: No, GWT DevMode is intended for development and debugging purposes only. For production deployments, you need to compile your GWT application into optimized JavaScript.

Summary

In this tutorial, you learned how to use GWT DevMode to run and debug GWT applications. You explored the steps involved in launching DevMode, accessing the DevMode UI, and utilizing its features for debugging and testing your application. GWT DevMode enhances your development process by providing code reloading, remote debugging, and interactive mode capabilities. By effectively using GWT DevMode, you can streamline your GWT application development and quickly identify and resolve issues.