JSP
is a java based Web Application development technology, which is an advancement
of the Java Servlets. Before JSP, java servlets was used for the server side
programming in which both the processing
of the requests and the generation of the response were handled by a single
servlet class. Java servlets uses HTML codes embedded in Java Codes , so it is
necessary for a programmer to have a thorough knowledge of java as well as HTML programming. Java Server
Pages(JSP) is a technology for
developing web pages that include dynamic content. As a HTML page can contains only
static content which always remains the same but a JSP page can change its
content based on any number of variable items, including the identity of the
user, the user's browser type, information provided by the user, and selections
made by the user.
A
JSP page contains standard markup language elements, such as HTML tags, just like
a regular web page as well as it also contains special JSP elements that allow
the server to insert dynamic content in the page. JSP elements can be used for a
variety of purposes, such as retrieving information from a database or
registering user preferences. When a user asks for a JSP page, the server
executes the JSP elements, merges the results with the static parts of the
page, and sends the dynamically composed page back to the browser.
Advantages of JSP over Servlets :- As
we found servlets more advantageous over CGI scripts because servlet do not
create process for all request, they create a thread which is lighter than a
process and in all thread the resources are shared so there is not separate
allocation of resources which in CGI all are treated as a separate process but
there is a problem of using servlet. Servlet needs
to recompile if any designing code is modified and doesn't provide separation
Presentation and Business logic, they are mixed up.
JSP offers various advantages over Java Servlet. It
provides a better server- side scripting support as compared to Java Servlet.
Java programmer can easily create servlet but it is a tough job for a web page
designer. A JSP page consists of HTML and some java code embedded in it. There
are some reasons for using JSP over
servlets.
·
It facilitates automatic recompilation of JSP
page by a web container for any update in the code
·
JSP allows to access a page easily as HTML
·
Allows to create a JSP page by using a simple
HTML template and the JSP page is automatically handled by JSP container.
Architecture of JSP Page:- there
are 2 approaches to build a web applications which are known as JSP MODEL I and
JSP MODEL II.
The JSP MODEL I Architecture:- in this architecture, a web browser
directly accesses JSP pages of a web
container which interact with JavaBean. The JSP or Servlet handles all the
responsibility of request processing such as validating the data, business
logic validation and processing, show error messages, finally generating the
view for the application.
JSP Model 1
architecture is good for very small application, but it's not a good solution
for big enterprise application. The JSP Model 1 architecture do not separate
the view, business processing logic and the view is tightly integrated with the
business logics.
Processing of Model I
1. When a client browser sends request from a the
JSP page
2. JSP accesses Java Bean and invokes business
logic and check which request parameters are invoked by the client request.
3. If generated response requires accessing of a
database, the JSP page uses a JavaBean for retrieving the data from the
database and get/save data
4. Response is sent to the browser which is
generated by JSP
The JSP MODEL II(MVC) Architecture Model 2 is based on the MVC (Model View
Controller) design pattern.
The MVC design consists of three modules model, view and
controller.
Model(Java Bean) The model represents the state (data) and business
logic of the application.
View(JSP) :- The view module is responsible to display
data i.e. it represents the presentation.
Controller (Servlet) :- The controller module acts as an interface
between view and model. It intercepts all the requests i.e. receives input and
commands to Model / View to change accordingly.
Processing of Model II
1. When a client browser sends request from a JSP
page. JSP create the view for the application and a
centralized Servlet is used to handle the entire request for the application
which works as the controller for the application.
2. This servlet instantiate Java Bean for processing the
business logic and getting the data (Model) from the database if required.
3. The controller servlet decides which JSP page to forward to
as a response.
4. A java bean instance invokes the database server if data is
needed from the server
5. Finally the selected JSP page render the view to the user.
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