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Servlet Interview Questions |
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Which code line
must be set before any of the lines that use the PrintWriter? |
setContentType() method must be set.
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Which protocol
will be used by browser and servlet to communicate ? |
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HTTP |
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In how many ways
we can track the sessions? |
Method 1) By URL rewriting
Method 2) Using Session object
Getting Session form HttpServletRequest object
HttpSession session = request.getSession(true);
Get a Value from the session
session.getValue(session.getId());
Adding values to session
cart = new Cart();
session.putValue(session.getId(), cart);
At the end of the session, we can inactivate the session by using the
following command
session.invalidate();
Method 3) Using cookies
Method 4) Using hidden fields |
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How Can You
invoke other web resources (or other servlet / jsp ) ? |
Servelt can invoke other Web resources in two
ways: indirect and direct.
Indirect Way : Servlet will return the resultant HTML to the browser
which will point to another Servlet (Web resource)
Direct Way : We can call another Web resource (Servelt / Jsp) from
Servelt program itself, by using RequestDispatcher object.
You can get this object using getRequestDispatcher("URL") method. You
can get this object from either a request or a Context.
Example :
RequestDispatcher dispatcher = request.getRequestDispatcher("/jspsample.jsp");
if (dispatcher != null)
dispatcher.forward(request, response);
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How Can you
include other Resources in the Response? |
Using include method of a RequestDispatcher
object.
Included WebComponent (Servlet / Jsp) cannot set headers or call any
method (for example, setCookie) that affects the headers of the
response.
Example : RequestDispatcher dispatcher =
getServletContext().getRequestDispatcher("/banner");
if (dispatcher != null)
dispatcher.include(request, response);
}
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What is
the difference between the getRequestDispatcher(String path)
ServletRequest interface and ServletContext interface? |
The getRequestDispatcher(String path)
method of 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 ServletContext
interface cannot accepts relative paths. All path must sart with
a "/" and are interpreted as relative to curent context root. If
the resource is not available, or if the server has not
implemented a RequestDispatcher object for that type of
resource, getRequestDispatcher will return null. Your servlet
should be prepared to deal with this condition.
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What is
the use of ServletContext ? |
Using ServletContext, We can access data
from its environment. Servlet context is common to all Servlets
so all Servlets share the information through ServeltContext.
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Is there
any way to generate PDF'S dynamically in servlets? |
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We need to use iText. A open source
library for java. Please refer sourceforge site for sample
servlet examples. |
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What is
the difference between using getSession(true) and
getSession(false) methods? |
getSession(true) - This method will check
whether already a session is existing for the user. If a session
is existing, it will return that session object, Otherwise it
will create new session object and return taht object.
getSession(false) - This method will check existence of session.
If session exists, then it returns the reference of that session
object, if not, this methods will return null.
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