Desktop Application Development – Java Web Start

Java Web Start is a technology that allows developers to deploy full-featured desktop applications over the internet or an intranet. It simplifies the process of launching Java applications, ensuring that users always have the latest version of the application without manual updates. In this article, we will explore Java Web Start, its key features, and how to create and deploy applications using this technology.

1. Introduction to Java Web Start

Java Web Start is a part of the Java Platform, which allows developers to create standalone Java applications that can be launched by clicking on a web page link or desktop icon. These applications run outside the browser, providing a more robust and consistent user experience.

2. Key Features of Java Web Start

Java Web Start offers several advantages for deploying desktop applications:

2.1. Easy Deployment

Developers can deploy applications on the web or an intranet, simplifying the distribution process. Users can access and launch applications with a single click, without the need for complex installation procedures.

2.2. Automatic Updates

Java Web Start automatically checks for updates when launching an application. If a new version is available, it will be downloaded and installed seamlessly, ensuring that users always have the latest features and security fixes.

2.3. Offline Access

Once an application is launched, it can continue to run even if the user loses their internet connection. This makes it suitable for both online and offline scenarios.

2.4. Security

Java Web Start applications run in a controlled environment, with security features such as sandboxing to prevent malicious code from harming the system. Users can grant or deny certain permissions for each application.

3. Creating a Java Web Start Application

Developing a Java Web Start application involves the following steps:

3.1. Application Code

Write the Java application code that you want to deploy. This code should be organized in a JAR (Java Archive) file, which includes all the necessary classes and resources.

3.2. JNLP File

Create a Java Network Launching Protocol (JNLP) file. This XML file describes your application and its resources, including the location of the JAR files, the main class, and additional security permissions.

3.3. Web Server

Host your JAR files, JNLP file, and additional resources on a web server that users can access. The JNLP file should be accessible via a URL.

3.4. Deployment Descriptor

On the web server, you should also provide a deployment descriptor that informs the server how to handle JNLP files. For example, for Apache Tomcat, you can use a .htaccess file to specify that JNLP files should be treated as application/x-java-jnlp-file content type.

4. Example of a JNLP File

Here’s a simplified example of a JNLP file:

<jnlp
  spec="1.0+"
  codebase="http://example.com/myapp"
  href="myapp.jnlp">
  <information>
    <title>My Java Web Start Application</title>
    <vendor>MyCompany</vendor>
  </information>
  <resources>
    <jar href="myapp.jar" />
  </resources>
  <application-desc main-class="com.mycompany.MyApp" />
  <security>
    <all-permissions />
  </security>
</jnlp>

This JNLP file defines the title, vendor, codebase, JAR file, main class, and security permissions for the application. Users can launch the application by accessing the JNLP file’s URL.

5. Launching a Java Web Start Application

When a user clicks on a link to the JNLP file or a desktop icon, Java Web Start will start the application by downloading the required JAR files. If an update is available, it will be downloaded and installed automatically. Once the application is launched, it runs independently, providing users with a seamless experience.

6. Conclusion

Java Web Start is a powerful technology for deploying and updating desktop applications over the web. It simplifies the distribution process, ensuring that users always have the latest version of the application. By following the steps outlined in this article, you can create and deploy your own Java Web Start applications, offering a consistent and user-friendly experience to your audience.