Servlet life cycle in java: A Servlet is a Java class that runs on a web server and is responsible for handling client requests and generating responses. The life cycle of a Servlet is a sequence of stages that start with its initialization and end with its destruction.
Servlet Initialization: When a Servlet is first loaded by the web server, its init() method is called. This method is used to perform any initialization tasks that are required before the Servlet can begin handling requests.
Request Processing: Once the Servlet is initialized, it can begin handling client requests. Each request is handled in its own thread, and the service() method of the Servlet is called to process the request. The service() method receives an HTTP request object and an HTTP response object as parameters, which it uses to generate the response.
Servlet Destruction: When the web server decides that the Servlet is no longer needed, it calls the destroy() method of the Servlet. This method can be used to perform any cleanup tasks that are required before the Servlet is unloaded
It is important to note that a single instance of a Servlet can handle multiple requests, so the init() and destroy() methods are only called once per instance of the Servlet. The service() method, on the other hand, is called once per request.In addition to these three stages, there are also two optional methods that can be implemented by a Servlet:
getServletConfig(): This method returns a ServletConfig object that contains any configuration information that was specified for the Servlet.
getServletInfo(): This method returns a string that provides information about the Servlet, such as its version number or purpose.
Overall, understanding the life cycle of a Servlet is important for developing effective and efficient Servlet-based web applications.
Servlet Life Cycle Diagram
Here’s a diagram that shows the life cycle of a Servlet in Java:
Servlet Interview Questions with Answers
Q.1 What is a Servlet?
Ans. A servlet is a Java programming language class that dynamically processes requests and responses to and from a web server.
Q.2 What is the difference between Servlets and JSPs?
Ans. JSPs are text files that are parsed and compiled into servlets at runtime. Servlets are Java classes that are compiled into bytecode.
Q.3 What is the lifecycle of a Servlet?
Ans. The lifecycle of a Servlet includes the following methods: init(), service(), and destroy().
Q.4 What is the difference between doGet() and doPost() methods?
Ans. doGet() method is used to retrieve information from the server, while doPost() method is used to send data to the server.
Q.5 What is a Servlet container?
Ans. A servlet container is a web server or application server that runs servlets and manages their lifecycle.
Q.6 What is the difference between a servlet context and a servlet config?
Ans. A servlet context is an object that contains information about the servlet container, while a servlet config is an object that contains information about the servlet.
Q.7 What is a request dispatcher?
Ans. A request dispatcher is an object that forwards a request from one servlet to another servlet or JSP.
Q.8 What is the difference between forward() and sendRedirect() methods?
Ans.The forward() method is used to forward a request to another servlet or JSP on the server side, while the sendRedirect() method is used to redirect the request to another URL on the client side.
Q.9 What is a filter?
Ans. A filter is a Java class that intercepts and processes requests and responses before they are sent to the servlet.
Q.10 What is a session?
Ans. A session is a way to maintain state information across multiple requests from the same client to the server. It is stored on the server and identified by a unique session ID