Jakarta Servlets: Behind the Scene of Deployment and container Lifecycle

Jakarta Servlets (formerly Java Servlets) are at the core of Java-based dynamic web applications, processing HTTP requests and responses. The Servlet Container (like Apache Tomcat or Jetty) manages the servlet lifecycle, enabling smooth communication between web servers and browsers.

Why Jakarta Servlets Matter
Despite Spring's dominance, servlets remain foundational to Java web development. Every request processed by Spring ultimately flows through a servlet. Understanding servlets helps developers better manage Java web applications.

Step 1: WAR File Deployment
The Servlet Container deploys WAR files, extracting Java class files, scanning for annotations (@WebServlet, @WebFilter), and processing web.xml configurations. This prepares the application for initialization.

Step 2: Creating Servlet Context
The Servlet Context is created, acting as a shared space where servlets, filters, and listeners interact. It stores global settings (e.g., database configurations) and is accessible throughout the application lifecycle.

Step 3: ServletContainerInitializer
The container looks for ServletContainerInitializer in META-INF/services, bootstrapping custom logic like dynamically registering servlets or filters using the onStartup() method.

Step 4: Initializing Listeners, Filters, and Servlets
The container initializes listeners, filters, and servlets. Filters intercept requests, and servlets are instantiated based on loadOnStartup configurations. Once initialized, the app is ready to handle requests.

Stay tuned for the next article on Jakarta Servlet lifecycle during request processing!

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