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What is JSP?
Describe its concept |
| JSP
is a technology that combines HTML/XML markup languages and elements
of Java programming Language to return dynamic content to the Web
client, It is normally used to handle Presentation logic of a web
application, although it may have business logic. |
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What are the lifecycle phases of a JSP? |
JSP
page looks like a HTML page but is a servlet. When presented with JSP
page the JSP engine does the following 7 phases.
- Page translation: -page is parsed, and a
java file which is a servlet is created.
- Page compilation: page is compiled into a
class file
- Page loading : This class file is loaded.
- Create an instance :- Instance of servlet
is created
- jspInit() method is called
- _jspService is called to handle service
calls
- _jspDestroy is called to destroy it when
the servlet is not required.
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What is a translation unit?
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| JSP
page can include the contents of other HTML pages or other JSP files.
This is done by using the include directive. When the JSP engine is
presented with such a JSP page it is converted to one servlet class
and this is called a translation unit, Things to remember in a
translation unit is that page directives affect the whole unit, one
variable declaration cannot occur in the same unit more than once, the
standard action jsp:useBean cannot declare the same bean twice in one
unit. |
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How is JSP used in the MVC model |
| JSP
is usually used for presentation in the MVC pattern (Model View
Controller ) i.e. it plays the role of the view. The controller deals
with calling the model and the business classes which in turn get the
data, this data is then presented to the JSP for rendering on to the
client. |
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What are context initialization
parameters |
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Context initialization parameters are specified by the
in the web.xml file, these are initialization parameter
for the whole application and not specific to any servlet or JSP.
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What is a output comment |
| A
comment that is sent to the client in the viewable page source. The
JSP engine handles an output comment as un-interpreted HTML text,
returning the comment in the HTML output sent to the client. You can
see the comment by viewing the page source from your Web browser.
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What is a Hidden Comment |
| A
comment that documents the JSP page but is not sent to the client. The
JSP engine ignores a hidden comment, and does not process any code
within hidden comment tags. A hidden comment is not sent to the
client, either in the displayed JSP page or the HTML page source. The
hidden comment is useful when you want to hide or “comment out”
part of your JSP page. |
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What is a Expression |
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Expressions are act as place holders for language expression,
expression is evaluated each time the page is accessed. |
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What is a Declaration |
| It
declares one or more variables or methods for use later in the JSP
source file. A declaration must contain at least one complete
declarative statement. You can declare any number of variables or
methods within one declaration tag, as long as semicolons separate
them. The declaration must be valid in the scripting language used in
the JSP file. |
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What is a Scriptlet |
| A
scriptlet can contain any number of language statements, variable or
method declarations, or expressions that are valid in the page
scripting language. Within scriptlet tags, you can declare variables
or methods to use later in the file, write expressions valid in the
page scripting language, use any of the JSP implicit objects or any
object declared with a
.
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What are the implicit objects |
List them. Certain objects that are available for the use in JSP
documents without being declared first. These objects are parsed by
the JSP engine and inserted into the generated servlet. The implicit
objects are:
- request
- response
- pageContext
- session
- application
- out
- config
- page
- exception
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What’s the difference between
forward and sendRedirect |
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When you invoke a forward request, the request is sent to another
resource on the server, without the client being informed that a
different resource is going to process the request. This process
occurs completely with in the web container And then returns to the
calling method. When a sendRedirect method is invoked, it causes the
web container to return to the browser indicating that a new URL
should be requested. Because the browser issues a completely new
request any object that are stored as request attributes before the
redirect occurs will be lost. This extra round trip a redirect is
slower than forward. |
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What are the different scope values
for the |
The
different scope values for
are:
- page
- request
- session
- application
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Why are JSP pages the preferred API
for creating a web-based client program
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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. |
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Is JSP technology extensible |
| Yes,
it is. JSP technology is extensible through the development of custom
actions, or tags, which are encapsulated in tag libraries.
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