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.

Note:

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?

No.	Get	Post
1	Data are submitted part of URL	Data are submitted inside body of servlet request.
2	Query max length is 255 character	No Limitation
3	Its not secure	Its secure.

5. 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.
6. 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.
7. 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.
8. 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.
9. 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.
10. 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
11. Difference between HttpServlet and Generic Servlet:

No.	Http Servlet	Generic Servlet
1	Parrent Class for Http Servlet is Generic Servlet	Parent class of HttpServlet is Servlet
2	Http Servlet support doget(),dopost(),doHead methods	Service method will handle all the request.

12. Difference between ServletContext and ServletConfig:

No.	Servlet Context	Servlet Config
1	Set of methods support to communicate with servlet container	Its specific to the single servlet.
2	Uses for set the attribute that other servlet in the same context can use.	Its used to initialize the servlet specific value.
3	It’s created when servlet container created.	It’s created when specific class is loaded by container.

13. 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.
13. what are the Information servletRequest object contain:
• parameter passed by the client
• name of the remote host
• the protocol
14. 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.

16. 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.

17. Servlet Chaining:

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

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