What Is Servlet?
Java
Servlet is a server side programming which used to
generating dynamic web pages and it also generates web page as a response of
the request received from browsers.
Java Servlet is a class which responds to a
particular type of network request - HTTP request.
All servlets must implement the javax.servlet.Servlet
interface which defines servlet life-cycle methods.
Java Servlet are programs that run on a Web server and it
work in the middle layer between a request coming from the Web browsers and
databases on the HTTP server.
How
Many Objects of a Servlet is created?
Only one object at the time of first request by
servlet or web container.
Web container manages the life cycle of a servlet
and helps to map the URL to a specific servlet and web container creates the
object of a servlet.
Do
we override service () method?
No!, we do not override the service() method.
What's
New Features Added to Servlet 3?
The main aims to offer Web developers greater
simplicity and ease of development while adhering to Web 2.0 principles.
1. Servlet
Annotations
2. Web
Fragments
3. Web
components addition dynamically
4. Asynchronous
Processing
5. Servlet
3 supports annotation to eliminate web.xml
1. @WebServlet
2. @WebServletContextListener
3. @ServletFilter
4. @InitParam
What
Is Difference Between Cookies and HttpSession?
The Cookie works at client side whereas
HttpSession works at server side.
How
do I get the server info in Servlet?
To get server info using the
getServletContext().getServerInfo()
How
to get the client’s IP address in Servlets?
To get client IP address using
request.getRemoteAddr()
What
Are Different Ways for Servlet Authentication?
1. HTTP
Basic Authentication
2. HTTP
Digest Authentication
3. HTTPS
Authentication
4. Form
Based Login
When
Servlet Object Is Created?
At the time of first request, the servlet object
created.
What
Are packages that work with Servlet?
There are two packages which work with Servlet:
One is - Javax.servlet and second one
is - Javax.servlet.http
A servlet life-cycle can be defined as the entire
process from its creation till the destruction. The Stages of the Servlet Life
Cycle:
1. Servlet
is loaded
2. Servlet
is instantiated
3. Servlet
is initialized
4. Service
the request
5. Servlet
is destroyed
Source - (http://www.javachain.com/servlet-life-cycle/)
How
Is a Servlet Implemented in code?
Simply extending the Httpservlet or generic
servlet class
What
Is the use of Generic Servlet?
The Generic Servlet can handle all type of
requests.
Is
Servlet Synchronized?
No!, the servlets are not synchronized. If you
want, we must implement SingleThreadInterface
Is
it possible to have a Constructor inside the Servlet?
Yes!, it is possible to define a constructor
inside a servlet, but it can be called only by Servlet container and not
explicitly.
What
Are the Servlet Life Cycle Methods?
There are three life cycle methods of a Servlet:
1. The
init() method - The init method is used to initialize the servlet.
2. The
service() method - The service method is used to service the request.
3. The
destroy() method - The destroy method invoked only once when servlet is
unloaded.
Finally, servlet is garbage collected by the
garbage collector of the JVM.
The service() method checks the HTTP request type
- GET, POST, PUT, DELETE and calls doGet, doPost, doPut, doDelete.
Example:
The prototype for the init() method:
Public void init(ServletConfig serObj)throws
ServletException{ }
Example:
The prototype for this method:
Public void service(ServletRequest req,
ServletResponse resp) throws ServletException, IOException { }
Example:
The prototype for this method:
Public void destroy() {}
How
Many times each Life Cycle method of a Servlet called?
The init()
method is called only once during the life cycle of servlet. Each time the
server receives a request for a servlet, the server spawns a new thread and
calls service() method.
Who
Is Responsible to create the Object of Servlet?
The web container and servlet container is
responsible to create the object.
What
Is Scope Object and How Many Types?
The Scope objects is use to share the information
among web components with the help of setattribute() and getattribute().
The Types of Scope Objects:
1. Web
Context
2. Session
3. Request
4. Page
What
All Protocols Are Supported by HTTPServlet?
HTTP protocol
HTTPS protocol
What
Kinds of HTTP Requests?
1. Get()
method
2. Post()
method
3. Head()
method
4. Options()
method
5. Put()
method
6. Trace()
method
7. Delete()
method
How
To Invalidate a Session in Servlet?
To invalidate session by calling
session.invalidate() method.
What
Are the Different Types of Session Tracking Mechanism supported by Servlets?
1. URL
rewriting
2. Hidden
Form Fields
3. Cookies
4. Secure
Socket Layer (SSL) Sessions
What
Is HTTPServletRequest class?
What
Is HTTPServletResponse class?
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