Running a Method/Class on Tomcat/Wildfly/Glassfish Startup
In the world of web development, Tomcat, Wildfly, and Glassfish are three of the most popular Java-based application servers used for hosting web applications. These servers provide a powerful platform for developers to deploy their applications, but what if you want to run a specific method or class when the server starts up? In this article, we will explore how to achieve this on Tomcat, Wildfly, and Glassfish.
Before diving into the technical details, let's first understand why you might need to run a method or class on server startup. There can be various reasons for this, such as initializing database connections, loading configuration files, or performing any other custom logic that needs to be executed before the application is fully functional. Running a method or class on server startup can save you time and effort in manually triggering these tasks every time the server is restarted.
Tomcat is a lightweight, open-source application server commonly used for hosting Java web applications. To run a method or class on Tomcat startup, you need to create a ServletContextListener. This listener is notified when the server starts up and shuts down, allowing you to perform any necessary tasks. To create a ServletContextListener, you need to implement the javax.servlet.ServletContextListener interface and override its contextInitialized() method. In this method, you can write the code to execute your desired method or class. Once the listener is created, you need to add it to the web.xml file of your application. This will ensure that the listener is invoked when the server starts up.
Moving on to Wildfly, which is an open-source, lightweight, and flexible application server built on top of the JBoss Enterprise Application Platform. Running a method or class on Wildfly startup is similar to Tomcat, but instead of a ServletContextListener, you need to create a javax.servlet.ServletContextListener implementation. This listener has an additional method, contextDestroyed(), which is used to perform any cleanup tasks when the server shuts down. Once the listener is created, you need to add it to the web.xml file of your application, just like in Tomcat.
Glassfish, on the other hand, is a full-featured Java EE application server with a robust and scalable architecture. To run a method or class on Glassfish startup, you need to create a javax.servlet.ServletContextListener implementation, just like in Wildfly. However, unlike Tomcat and Wildfly, Glassfish provides an alternate way of adding the listener. You can add the listener through the Glassfish admin console by navigating to the Applications tab, selecting your application, and clicking on the "Manage Servlets" button. You can then add the listener to the application's initialization parameters.
In conclusion, running a method or class on server startup is a useful feature that can save you time and effort. Whether you are using Tomcat, Wildfly, or Glassfish, the process of achieving this is similar, but with some minor differences. By following the steps outlined in this article, you can easily run your desired method or class on startup and streamline your web application deployment process. So, the next time you need to perform any initialization tasks, don't forget to utilize this handy feature.
