servlets life cycle

The life cycle of a servlet consists of several phases that occur when the servlet is loaded, initialized, and handling client requests. The following are the main phases of the servlet life cycle:

1. Loading: When a servlet container starts up or receives a request for a servlet for the first time, it loads the servlet class into memory. This involves finding the servlet class, verifying its integrity, and creating an instance of it.

2. Initialization: After the servlet class is loaded, the servlet container calls the servlet's init() method to initialize it. The init() method is typically used to perform any initialization tasks required by the servlet, such as opening a database connection or initializing other resources.

3. Handling Requests: Once the servlet is initialized, it is ready to handle client requests. The servlet container receives HTTP requests from clients and maps them to the appropriate servlet based on the URL pattern defined in the web.xml file or using annotations.

4. Servicing Requests: When a client request is received, the servlet container creates a new thread to handle the request and invokes the servlet's service() method. The service() method is responsible for generating a response to the client request. Depending on the request method (e.g., GET, POST), the service() method will call the appropriate HTTP method (doGet(), doPost(), etc.) to handle the request.

5. Destroying: When the servlet container is shutting down or the web application is undeployed, the container calls the servlet's destroy() method to allow the servlet to perform any clean-up tasks, such as closing database connections or releasing other resources.

6. Unloading: When the servlet container is no longer using a servlet instance, it unloads the servlet instance from memory by calling its unload() method. This method allows the servlet to perform any final clean-up tasks before the servlet instance is discarded.