JSP Interview Questions and Answers
What is a JSP and what is it used for?
Java Server Pages (JSP) is a platform independent presentation layer
technology that comes with SUN s J2EE platform. JSPs are normal HTML
pages with Java code pieces embedded in them. JSP pages are saved to *.jsp
files. A JSP compiler is used in the background to generate a Servlet
from the JSP page.
What is difference between custom JSP tags and beans?
Custom JSP tag is a tag you defined. You define how a tag, its
attributes and its body are interpreted, and then group your tags into
collections called tag libraries that can be used in any number of JSP
files. To use custom JSP tags, you need to define three separate
1. the tag handler class that defines the tag\'s behavior
2. the tag library descriptor file that maps the XML element names to
the tag implementations
3. the JSP file that uses the tag library
When the first two components are done, you can use the tag by using
<%@ taglib uri="xxx.tld" prefix="..." %>
Then you are ready to use the tags you defined. Let's say the tag prefix
JavaBeans are Java utility classes you defined. Beans have a standard
format for Java classes. You use tags to declare a bean and use to set
value of the bean class and use to get value of the bean class.
Custom tags and beans accomplish the same goals -- encapsulating complex
behavior into simple and accessible forms. There are several
Custom tags can manipulate JSP content; beans cannot.
Complex operations can be reduced to a significantly simpler form with
custom tags than with beans. Custom tags require quite a bit more work
to set up than do beans.
Custom tags usually define relatively self-contained behavior, whereas
beans are often defined in one servlet and used in a different servlet
or JSP page.
Custom tags are available only in JSP 1.1 and later, but beans can be
used in all JSP 1.x versions.
What are the two kinds of comments in JSP and what's the difference
between them ?
<%-- JSP Comment --%>
<!-- HTML Comment -->
What is JSP technology?
Java Server Page is a standard Java extension that is defined on top of
the servlet Extensions. The goal of JSP is the simplified creation and
management of dynamic Web pages. JSPs are secure, platform-independent,
and best of all, make use of Java as a server-side scripting language.
What is JSP page?
A JSP page is a text-based document that contains two types of text:
static template data, which can be expressed in any text-based format
such as HTML, SVG, WML, and XML, and JSP elements, which construct
What are the implicit objects?
Implicit objects are objects that are created by the web container and
contain information related to a particular request, page, or
application. They are:
How many JSP scripting elements and what are they?
There are three scripting language elements:
Why are JSP pages the preferred API for creating a web-based client
Because no plug-ins or security policy files are needed on the client
systems(applet does). Also, JSP pages enable cleaner and more module
application design because they provide a way to separate applications
programming from web page design. This means personnel involved in web
page design do not need to understand Java programming language syntax
to do their jobs.
Is JSP technology extensible?
YES. JSP technology is extensible through the development of custom
actions, or tags, which are encapsulated in tag libraries.
Can we use the constructor, instead of init(), to initialize servlet?
Yes , of course you can use the constructor instead of init(). There’s
nothing to stop you. But you shouldn’t. The original reason for init()
was that ancient versions of Java couldn’t dynamically invoke
constructors with arguments, so there was no way to give the constructur
a ServletConfig. That no longer applies, but servlet containers still
will only call your no-arg constructor. So you won’t have access to a
ServletConfig or ServletContext.
How can a servlet refresh automatically if some new data has entered the
You can use a client-side Refresh or Server Push.
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