Jsp Introduction Tutorial

Java Server Page

• Deisigned By:
• Shivendra Srivastwa
• Java and Android consultant

Java Server Page (JSP)
JSP technology is used to create web
application just like Servlet technology. It
can be thought of as an extension to the
servlet because it provides more
functionality than servlet.
 A JSP page contains HTML code and
JSP tags. The jsp pages are easier to
maintain than servlet because we can
separate designing and development. It
provides some additional features such
as Expression Language, Custom Tag
etc.


Advantage of JSP over
Servlet
JSP is the extension to the servlet
technology. We can use all the features of
Servlet in JSP.
 In addition to, we can use implicit
objects, predefined tags, expression
language and Custom tags in JSP, that
makes JSP development easy.
 JSP can be easily managed because we can
easily separate our business logic with
presentation logic. In servet, we mix our
business logic with the presentation logic.
 If JSP page is modified, we don't need to
redeploy the project. The servlet code needs
to be updated and recompiled if we have to
change the look and feel of the application.


Life cycle of a JSP Page







Compilation of JSP Page
Classloading (class file is loaded by the
classloader)
Instantiation (Object of the Generated
Servlet is created).
Initialization ( jspInit() method is invoked
by the container).
Reqeust processing ( _jspService()
method is invoked by the container).
Destroy ( jspDestroy() method is invoked
by the container)

JSP page is translated into servlet by the help of JSP
translator. The JSP translator is a part of webserver that is
responsible to translate the JSP page into servlet. Afterthat
Servlet page is compiled by the compiler and gets converted
into the class file. Moreover, all the processes that happens in
servlet is performed on JSP later like initialization, commiting
response to the browser and destroy.

The JSP API
The JSP API consists of two packages:
1. javax.servlet.jsp package
2. javax.servlet.jsp.tagext

javax.servlet.jsp package
The Interfaces are as follows:
1. JspPage
HttpJspPage
The classes are as follows:
1. JspWriter
2. PageContext
3. JspFactory
4.JspEngineInfo
5.JspExceptionJspError

2.

According to the JSP
specification, all the generated
servlet classes must
implement the JspPage
interface. It extends the Servlet
interface. It provides two life
cycle methods.

The JspPage interface

METHODS OF JSPPAGE
INTERFACE
public void jspInit()
It is invoked only
once during the life
cycle of the JSP
when JSP page is
requested firstly. It
is used to perform
initialization. It is
same as the init()
method of Servlet
interface.

public void
jspDestroy():
It is invoked only
once during the life
cycle of the JSP
before the JSP
page is destroyed.
It can be used to
perform some clean
up operation.

THE HTTPJSPPAGE
INTERFACE
public void _jspService():
It is invoked each time when request for
the JSP page comes to the container. It
is used to process the request. The
underscore _ signifies that you cannot
override this method.

JSP scripting Element
The scripting elements provides the
ability to insert java code inside the
jsp. There are three types of scripting
elements:
 Scripting elements:


◦ 1. scriptlet tag
◦ 2. expression tag
◦ 3. declaration tag

Scriptlet tag
A scriptlet tag is used to execute java
source code in JSP. Syntax is as
follows:
 Syntax:
<% java source code %>


JSP expression tag
The code placed within expression tag
is written to the output stream of the
response.
 So you need not write out.print() to
write data. It is mainly used to print the
values of variable or method.
 Syntax: <%= statement %>


JSP declaration tag
The JSP declaration tag is used to
declare fields and methods. The code
written inside the jsp declaration tag is
placed outside the service() method of
auto generated servlet. So it doesn't
get memory at each request
 Syntax:
<%! statement %>


Difference between the jsp
scriptlet tag and jsp declaration
tag

The jsp scriptlet tag can only declare
variables not methods whereas jsp
declaration tag can declare variables
as well as methods.
 The declaration of scriptlet tag is
placed inside the _jspService()
method whereas the declaration of jsp
declaration tag is placed outside the
_jspService() method.


Implicit Object


There are 9 implicit objects available
for the JSP page. The Auto Generated
Servlet contains many objects like out,
request, config, session, application
etc.

out implicit object
For writing any data to the buffer, JSP
provides an implicit object named out.
 Syntax:


 out.print();

request implicit object
In JSP, request is an implicit object of
type HttpServletRequest. Let's see the
simple example of request implicit
object where we are printing the name
of the user with welcome message.
 eg: request.getParameter


response implicit object


In JSP, response is an implicit object
of type HttpServletResponse. Let's
see the example of response implicit
object where we are redirecting the
request to the Google.

config implicit object
In JSP, config is an implicit object of
type ServletConfig. This object can be
used to get configuration information
for a particular JSP page.
 This variable information can be used
for one jsp page only.


application implicit object


In JSP, application is an implicit object
of type ServletContext.This object can
be used to get configuration
information from configuaration
file(web.xml). This variable information
can be used for all jsp pages.

session implicit object


In JSP, session is an implicit object of
type HttpSession.The Java developer
can use this object to set,get or
remove attribute or to get session
information.

pageContext implicit object
In JSP, pageContext is an implicit
object of type PageContext class.The
pageContext object can be used to
set,get or remove attribute from one of
the following scopes:
 i. Page
ii. Request
 Iii. Session iv. Application
 Note: page scope is the default scope


exception implicit object


In JSP, exception is an implicit object
of type java.lang.Throwable class.
This object can be used to print the
exception. But it can only be used in
error pages.It is better to learn it after
page directive. Let's see a simple
example:

Happy Programming with JSP
Thanks…………

Jsp Introduction Tutorial

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Jsp Introduction Tutorial