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Thursday, November 19, 2009

Servlet Question and Answer

When I will prepare for technical interview, I have used to think about hints and opt technical terms.

So I have started preparing question while reading books. I will ask question my self and redo the answer until I get opt technical words.

This post all are my own preparation if any one find its use full I really deserve for that.

Visitors of my blogspot kindly add your valuable comments to improve my post.


If u find any answer is wrong let me know. So I can redefine the same.

  1. What is Servlet?
    • Servlet is a java program, It will run inside the web container
    • Servlet extends request/respond –oriented servers such as java oriented web server.
  2. Different way to session tracking?
    • Cookies
    • URL re-writings
    • Http session tracking
    • Hidden form
    • Session
  3. What mechanism is used by servlet container to maintain the session?
    • Session
    • Cookies
    • URL re-writing
  4. Difference between GET and POST?





Data are submitted part of URL

Data are submitted inside body of servlet request.


Query max length is 255 character

No Limitation


Its not secure

Its secure.

  1. Session
    • Session is a object is used to track the information about the user with web application across multiple HTTP Request (State less).
    • Session is stored on web server.
  2. Servlet Mapping
    • Mapping defines the association between the URL pattern and Servlet
    • Mapping will be define in web.xml
    • Mapping is used to map the particular request to Servlet.
  3. Servlet Context:
    • It’s a servlet Object that contains information about web application and container.
    • Each application has only one servlet Context Object.
    • Uses for set the attribute that other servlet in the same context can use.
  4. Can we use constructer instead of Init():
    • Yes we can use constructer in Servlet
    • But we wont get servlet specific feature
    • So we can’t use servletcontext and servletconfig object in constructer.
  5. Life cycle method of the servlet:
    • Javax.servlet.Servlet interface providing 3 life cycle methods are
    • Public void init (ServletConfig config)- will be called when instance is created.
    • Public void service(ServletRequest req,ServletResponse res)-Every request is handled by service method only.
    • Public void distory()-when object is de-allocated from JVM.
  6. Pre Initialization of a servlet:
    • Process of loading servlet before any request comes in is called pre loading/pre initialization.
    • We have to include the element priority for every servlet in web.xml
  7. Difference between HttpServlet and Generic Servlet:


Http Servlet

Generic Servlet


Parrent Class for Http Servlet is Generic Servlet

Parent class of HttpServlet is Servlet


Http Servlet support doget(),dopost(),doHead methods

Service method will handle all the request.

  1. Difference between ServletContext and ServletConfig:


Servlet Context

Servlet Config


Set of methods support to communicate with servlet container

Its specific to the single servlet.


Uses for set the attribute that other servlet in the same context can use.

Its used to initialize the servlet specific value.


It’s created when servlet container created.

It’s created when specific class is loaded by container.

  1. Advantages and selling point of Servlet?

    • Servlet handle the multiple requests and synchronize the request.
    • This allows servlet to support online real time conferencing.
    • Servlet forward the request to the other servlet.
    • So servlet can be used to balance the load among several servers that mirror the same content.
  1. what are the Information servletRequest object contain:
    • parameter passed by the client
    • name of the remote host
    • the protocol
  2. Type of constraints send on the client : by servlet Response interface

    • Content length
    • Content type
    • Servlet Writer, Servlet output stream and a writer through which the servlet can send the data.

  1. Context Initialization Parameter:
    • It’s specified in web.xml under the element.
    • This is a parameter for the whole application not specific for Servlet/JSP.
    • It will be only accessed by servlet context object.

  1. Servlet Chaining:

    • Two are more servlet co-operate in servicing a single request.

  1. Difference between Servlet Context and Page Context?
    • ServletContext –Gives information about Servlet container
    • PageContext-Gives information about request
  2. Difference:
    • Request.getRequestDispacher()-Need to give relative path.
    • Context.getRequestDispacher()-Need to give absolute path.
  3. Difference:
    • RequestDispacher()-Direct with request and Response object.
    • sendRequest()-direct with new request and Response object.