Collection of large number of Servlet Interview Questions. These questions are frequently asked in the Java Interviews.
Question: What is a Servlet?
Answer: Java Servlets are server side components that provides a powerful mechanism for developing server side of web application. Earlier CGI was developed to provide server side capabilities to the web applications. Although CGI played a major role in the explosion of the Internet, its performance, scalability and reusability issues make it less than optimal solutions. Java Servlets changes all that. Built from ground up using Sun's write once run anywhere technology java servlets provide excellent framework for server side processing.
Question: What are the types of Servlet?
Answer: There are two types of servlets, GenericServlet and HttpServlet. GenericServlet defines the generic or protocol independent servlet. HttpServlet is subclass of GenericServlet and provides some http specific functionality linke doGet and doPost methods.
Question: What are the differences between
HttpServlet and Generic Servlets?
Answer: HttpServlet Provides an abstract class to be subclassed to create an HTTP servlet suitable for a Web site. A subclass of
must override at least one method, usually one of these:
doGet, if the servlet supports HTTP GET requests
doPost, for HTTP POST requests
doPut, for HTTP PUT requests
doDelete, for HTTP DELETE requests
destroy, to manage resources that are held for the life of the servlet
getServletInfo, which the servlet uses to provide information about itself
There's almost no reason to override the
handles standard HTTP requests by dispatching them to the handler methods for
each HTTP request type (the
doXXX methods listed above).
Likewise, there's almost no reason to override the
GenericServlet defines a generic, protocol-independent servlet. To
write an HTTP servlet for use on the Web, extend
GenericServlet implements the
GenericServlet may be directly extended by a servlet,
although it's more common to extend a protocol-specific subclass such as
GenericServlet makes writing servlets easier. It provides simple
versions of the lifecycle methods
of the methods in the
also implements the
log method, declared in the
To write a generic servlet, you need only override the abstract
Question: Differentiate between Servlet and
Answer: Servlets are server side components that executes on the server whereas applets are client side components and executes on the web browser. Applets have GUI interface but there is not GUI interface in case of Servlets.
Question: Differentiate between doGet and doPost
Answer: doGet is used when there is are requirement of sending data appended to a query string in the URL. The doGet models the GET method of Http and it is used to retrieve the info on the client from some server as a request to it. The doGet cannot be used to send too much info appended as a query stream. GET puts the form values into the URL string. GET is limited to about 256 characters (usually a browser limitation) and creates really ugly URLs.
POST allows you to have extremely dense forms and pass that to the server without clutter or limitation in size. e.g. you obviously can't send a file from the client to the server via GET. POST has no limit on the amount of data you can send and because the data does not show up on the URL you can send passwords. But this does not mean that POST is truly secure. For real security you have to look into encryption which is an entirely different topic
Question: What are methods of HttpServlet?
Answer: The methods of HttpServlet class are :
* doGet() is used to handle the GET, conditional GET, and HEAD requests
* doPost() is used to handle POST requests
* doPut() is used to handle PUT requests
* doDelete() is used to handle DELETE requests
* doOptions() is used to handle the OPTIONS requests and
* doTrace() is used to handle the TRACE requests
Question: What are the advantages of Servlets
over CGI programs?
Answer: Question: What are methods of HttpServlet?
Answer: Java Servlets have a number of advantages over CGI and other API's. They are:
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