24-02-25
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Q)What is JSP?
=>JSP is a Java based web technology from Sun Microsystems.
Q)What is the purpose of JSP technology?
=>JSP technology is used to develop Java based dynamic websites.
OR
=>In Java based web application development JSP technology is used.
Q)What is a jsp?
=>A jsp is a dynamic web resource that enahances the functionality of the
web server.
=>A jsp is a JSP Container managed web server side piece of code(server side program).
=>A jsp is a web component.
=>A jsp is a a text file with any name but with ".jsp extension.
Q)What can a jsp do in a Java web application?
=>All that a servlet can do.
Q)Can a jsp replace a servlet?
=>Yes. But it will not do.
Note:- In fact, each use-case is implemented using a servlet and a jsp together.
Q)When there is already Servlet technology, what was the need of JSP technology?
=>servlets are weak in presentation. JSP is excellent in that.
Q)What are the constituents (contents) of a jsp?
A jsp=HTML code+Scripting elements+Java code
Q)What is the life cycle of a jsp?
=>JSP container controls the life cycle of a jsp.
=>jsp development is nothing but instead of we developing a servlet, asking
the JSP container to write a servlet for us.
1)translation phase
2)compilation phase
3)instantiation phase
4)initialization phase
5)servicing phase
6)destruction phase
Q)Explain about Scripting elements.
=>JSP Scripting elements are those JSP
elements using which, Java code is directly
embeded into a jsp.
=>Scripting elements are of 3 types.
1.)declaration
2.)expression
3.)scriptlet
=>JSP declaration is one of the three JSP scripting elements.
=>It is used to place Java code directly within the source code of a jsp.
=>A JSP declaration starts with <%! and ends with %>
=>With in a JSP declaration we can place Java variables and Java methods.
=>During translation phase, Java variables and Java methods of the JSP declaration become the members of the page implementation
class. i.e. container generated servlet.
expression
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=>JSP expression is one of the three JSP scripting elements.
=>It is used to place Java code directly within the source code of a jsp.
=>A JSP expression starts with <%= and ends with %>
=>Within a JSP expression we can write only one Java expression(that too without semi colon).
For eg.
a.) <%= a+b %>
b.) <%= request.getParameter("username") %>
c.) <%= sum %>
=>During translation phase, Java expression of a JSP expression is placed in the servicing method of page implementation class.
=>We can have any number of JSP expressions in a jsp. In the same order their Java code will be placed in the servicing method.
=>When a JSP expression is executed, 2 things happen in the background.
1.)Java expression is evaluated.
2.)evaluated value is written to the
browser stream.
scriptlet
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=>JSP scriptlet is one of the three JSP scripting elements.
=>It is used to place Java code directly within the source code of a jsp.
=>A JSP scriptlet starts with <% and ends with %>
=>We can place free form of Java code in a JSP scriptlet. i.e. during servlet programming whatever Java code we write in servicing method to implement the use-case, all that Java code we can write in a JSP scriptlet.
For eg.
<%
String a=request.getParameter("t1");
String b=request.getParameter("t2");
int n1=Integer.parseInt(a);
int n2=Integer.parseInt(b);
...
%>
=>During translation phase, Java code of a JSP Scriptlet is placed in the srvicing method of page implementation class.
Q)What are the frequently used implicit objects in a jsp?
1)request
2)application
3)session
4)out
Q)Modify "additionapplication" so as to make use of a jsp in place of the servlet.
jspadditionapplication
numbers.html
addition.jsp
WEB-INF
web.xml
http://localhost:8081/jspadditionapplication/numbers.html
numbers.html
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Addition user interface
web.xml
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Note:- jsp need not be registered with the container.
addition.jsp
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Addition user interface
Q)Explain about MVC architecture of Java web application development.
=>A Java web application contains 3 different logics
1)flow control logic(application loigc)
2)data accessing and data processing logic
3)Presentation logic(output generation logic)
=>In MVC(Model, View, Controller) architecture of attending a client request,
=>data accessing and data processing logic are implemented in
a Java object known as Model.
=>Model is divided into two components.
1)Business Component(service Object)
2)Data Access Object
=> Flow control logic(application logic) is implemented
in controller.
=>A servlet acts as a controller as per MVC architecture.
=>What user sees is view. View Component produces the view
for the users. In a Java web application, a jsp is used as a view component.
MVC Diagram
1:- controller receiving the client request
2:- controller asks the model for processed data
3:- Model gives processed data to the controller
4:- controller swithing the control to the view component
5:- view component producing the response page for the client