Servlet Lifecycle

In Java, a Servlet is a server-side component that handles requests and generates responses. The lifecycle of a servlet is managed by the Servlet container (like Tomcat or Jetty), which is responsible for creating, initializing, handling requests, and destroying servlets. The lifecycle is defined by a series of stages:

Loading and Instantiation

• The servlet container loads the servlet class when the first request is made, or when explicitly configured to load at startup.
• The container creates an instance of the servlet by calling its default constructor.

Initialization (init() method)

• Once the servlet instance is created, the container calls the init() method.
• This method is used for servlet initialization, such as setting up resources or reading configuration data.
• The init() method is called only once during the servlet’s lifecycle, immediately after the servlet is created.

Request Handling (service() method)

• After initialization, the servlet is ready to handle client requests.
• The service() method is called for every request, which takes a request and response object as parameters.
• This method processes the request and sends back an appropriate response.
• The servlet can handle multiple requests concurrently, as each request is processed in its own thread.

Destruction (destroy() method)

• When the servlet is no longer needed, or the server shuts down, the container calls the destroy() method.
• This method is used for cleanup tasks like releasing resources (database connections, file handles, etc.).
• The destroy() method is called only once before the servlet is unloaded from memory.