INTERVIEW QUESTIONS J2EE SERVLET DETAILS

Question: What is the servlet life cycle?

Answer: Each servlet has the same life cycle:
A server loads and initializes the servlet (init())
The servlet handles zero or more client requests (service())
The server removes the servlet (destroy()) (some servers do this step only when they shut down).

Each servlet has the same life cycle:
A server loads and initializes the servlet (init())
The servlet handles zero or more client requests (service())
The server removes the servlet (destroy()) (some servers do this step only when they shut down). Source: CoolInterview.com

The Web container is responsible for managing the servlet’s life cycle. The Web container creates an instance of the servlet and then the container calls the init() method. At the completion of the init() method the servlet is in ready state to service requests from clients. The container calls the servlet’s service() method for handling each
request by spawning a new thread for each request from the Web container’s thread pool. Before destroying the instance the container will call the destroy() method. After destroy() the servlet becomes the potential candidate for garbage collection. Source: CoolInterview.com

The Life Cycle of a Servlet

Each servlet has the same life cycle:

* A server loads and initializes the servlet
* The servlet handles zero or more client requests
* The server removes the servlet(some servers do this step only when they shut down)

Initializing a Servlet

When a server loads a servlet, the server runs the servlet's init method. Initialization completes before client requests are handled and before the servlet is destroyed.

Even though most servlets are run in multi-threaded servers, servlets have no concurrency issues during servlet initialization. The server calls the init method once, when the server loads the servlet, and will not call the init method again unless the server is reloading the servlet. The server can not reload a servlet until after the server has destroyed the servlet by calling the destroy method.



Interacting with Clients

After initialization, the servlet is able to handle client requests. This part of the servlet life cycle was handled in the previous lesson.



Destroying a Servlet

Servlets run until the server are destroys them, for example, at the request of a system administrator. When a server destroys a servlet, the server runs the servlet's destroy method. The method is run once; the server will not run that servlet again until after the server reloads and reinitializes the servlet.

When the destroy method runs, another thread might be running a service request. The Handling Service Threads at Servlet Termination lesson shows you how to provide a clean shutdown when there could be long-running threads still running service requests.


Source: CoolInterview.com

init ---- servlet initializes and searches for dd(deployment descriptor) in which startup parameters are given
Service ----- servlet starts serving
Destroy ----- servlet terminates itself from processing
These are three methods of servlet life cycle .
Source: CoolInterview.com

the following steps manage the servlet life cycle -:

1)whenever a request hits the web container the container looks for the servlet which is called in web.xml file also called deployment descriptor.
2)then it loads the appropriate servlet by calling class.forName()method.
3)if no instance is running then it create instance.
4)initialize the servlet by calling init()method.
5)it then processes request by service()method.
6)it then destroy the instances by calling destroy() method.
7)unloads the servlet.
Source: CoolInterview.com

Servlet life cycle fall on 3 steps :

1)public void init(ServletConfig config)throws ServletExcpeion
2)public void service(ServletRequest req, ServletResponse res)throws ServletExcpeion, IOException
3)public void destroy()

Web server call the init() method when loading the servlet. This method typically establishes database connection.
Request comes from client handled by service() method then send it to doXXX() methods in the case of HTTPServlet.
destroy() method call when application stopped or servlet container shuts down. Source: CoolInterview.com

If you have the better answer, then send it to us. We will display your answer after the approval.

Rules to Post Answers in CoolInterview.com:-

• There should not be any Spelling Mistakes.
• There should not be any Gramatical Errors.
• Answers must not contain any bad words.
• Answers should not be the repeat of same answer, already approved.
• Answer should be complete in itself.

Name :*
Email Id :*
Answer :*
Verification Code	Not readable? Load New Code
Enter the above shown code: *
	Inform me about updated answers to this question