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| Servlet
Interview Questions |
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| Q: |
Explain
the life cycle methods of a Servlet. |
| A: |
The javax.servlet.Servlet interface defines
the three methods known as life-cycle method.
public void init(ServletConfig
config) throws ServletException
public void service( ServletRequest req,
ServletResponse res) throws ServletException,
IOException
public void destroy()
First the servlet is constructed, then initialized
wih the init()
method.
Any request from client are handled initially
by the service()
method before delegating to the doXxx()
methods in the case of HttpServlet.
The servlet is removed from service, destroyed
with the destroy()
methid, then garbaged collected and finalized. |
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| Q: |
What
is the difference between the getRequestDispatcher(String
path) method of javax.servlet.ServletRequest
interface and javax.servlet.ServletContext
interface? |
| A: |
The getRequestDispatcher(String path) method
of javax.servlet.ServletRequest interface
accepts parameter the path to the resource
to be included or forwarded to, which can
be relative to the request of the calling
servlet. If the path begins with a "/"
it is interpreted as relative to the current
context root.
The getRequestDispatcher(String path) method
of javax.servlet.ServletContext interface
cannot accepts relative paths. All path
must sart with a "/" and are interpreted
as relative to curent context root. |
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| Q: |
Explain
the directory structure of a web application. |
| A: |
The directory structure of a web application
consists of two parts.
A private directory called WEB-INF
A public resource directory which contains
public resource folder.
WEB-INF folder consists of
1. web.xml
2. classes directory
3. lib directory |
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|
| Q: |
What
are the common mechanisms used for session
tracking? |
| A: |
Cookies
SSL sessions
URL- rewriting |
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|
|
| Q: |
Explain
ServletContext. |
| A: |
ServletContext interface is a window for
a servlet to view it's environment. A servlet
can use this interface to get information
such as initialization parameters for the
web applicationor servlet container's version.
Every web application has one and only one
ServletContext and is accessible to all
active resource of that application. |
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| Q: |
What
is preinitialization of a servlet? |
| A: |
A container doesnot initialize the servlets
ass soon as it starts up, it initializes
a servlet when it receives a request for
that servlet first time. This is called
lazy loading. The servlet specification
defines the <load-on-startup> element,
which can be specified in the deployment
descriptor to make the servlet container
load and initialize the servlet as soon
as it starts up. The process of loading
a servlet before any request comes in is
called preloading or preinitializing a servlet. |
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[
Received from Amit Bhoir ] |
|
| Q: |
What
is the difference between Difference between
doGet() and doPost()? |
| A: |
A doGet() method is limited with 2k of data
to be sent, and doPost() method doesn't
have this limitation. A request string for
doGet() looks like the following:
http://www.allapplabs.com/svt1?p1=v1&p2=v2&...&pN=vN
doPost() method call doesn't need a long
text tail after a servlet name in a request.
All parameters are stored in a request itself,
not in a request string, and it's impossible
to guess the data transmitted to a servlet
only looking at a request string. |
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[
Received from Amit Bhoir ] |
|
| Q: |
What
is the difference between HttpServlet
and GenericServlet? |
| A: |
A GenericServlet has a service() method
aimed to handle requests. HttpServlet extends
GenericServlet and adds support for doGet(),
doPost(), doHead() methods (HTTP 1.0) plus
doPut(), doOptions(), doDelete(), doTrace()
methods (HTTP 1.1).
Both these classes are abstract. |
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[
Received from Amit Bhoir ] |
|
| Q: |
What
is the difference between ServletContext
and ServletConfig? |
| A: |
ServletContext: Defines
a set of methods that a servlet uses to
communicate with its servlet container,
for example, to get the MIME type of a file,
dispatch requests, or write to a log file.The
ServletContext object is contained within
the ServletConfig object, which the Web
server provides the servlet when the servlet
is initialized
ServletConfig:
The object created after a servlet is instantiated
and its default constructor is read. It
is created to pass initialization information
to the servlet. |
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[
Received from Sivagopal Balivada ]
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| Servlet
Interview Questions |
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