Java Server Pages
JSP:
JSP stands
for Java Server Pages.
JSP is a
specification for developing applications with Java programming language.
JSP
Engine:
JSP Engine
is a piece of software and converts JSP into a Servlet
There are
three phases in JSP Architecture:
1) Conversion 2)
Compilation 3)Execution
1) JSP
converted into a Servlet by JSP Engine.
2) Converted
Servlet compiled by Java Compiler
3) Servlet Excecuted
by Java Runtime Environment and output captured like HTML.
4) Jasper is
a JSP Engine name in Tomcat Server
5) Catalina
is a Web Container name in Tomcat Server
JSP Benefits:
1) Content and display logic separated
2) Simplifying web application development
by using JSP with Java beans and custom tags.
3) Recompiles automatically whenever
changes are made in JSP
4) Easier to write and develop web
applications
Converted
Servlet Life Cycle Methods:
1) jspInit()
2)_jspService() 3)jspDestroy()
jspInit():
It is called
by web container whenever first request comes to a servlet.
_jspService():
It is called
by web container for every request.
jspDestroy():
It is called
by web container whenever web application is undeployed from server or server
shuts down.
JSP
Elements:
JSP elements
are used to write JSP programs. JSP Elements are divided into three categories.
1) Scripting Elements
2) Directives
3) Actions
Scripting
Elements:
There are
four scripting elements in JSP:
1) Scriptlets
2) Declarations 3)Expressions 4) Comments
1)
Scriptlets:
Syntax:
<% …………….
%>
(or)
<jsp:scriptlet>
============
=> Java Code
</jsp:scriptlet>
2)
Declarations:
Syntax:
<%!
……………. %>
(or)
<jsp:declaration>
============
=> Java Code
</jsp:declaration>
3)
Expressions:
Syntax:
<%=
……………. %>
(or)
<jsp:expression>
============
=> Java Code
</jsp:expression>
4)
Comments:
Syntax:
<%--
…………. --%>
JSP
Implicit Object References:
There are 9 implicit
object references are present in JSP. They are ready to use.
1) “out” is an object reference of JspWriter
2) “request” is an object reference of
HttpServletRequest
3) “response” is an object reference of
HttpServletResponse
4) “config” is an object reference of
ServletConfig
5) “application” is an object reference of
ServletContext
6) “page” is an object reference of Object
7) “pageContext” is an object reference of
PageContext
8) “session” is an object reference of
HttpSession
9) “exception” is an object reference of
Throwable
JSP
Programs:
1)
JSP program to display welcome message:
<%
out.println("Welcome to JSP"); %>
2)
JSP program using HTML:
<html>
<body
bgcolor=red text=yellow>
<h1><%
out.println("Welcome"); %>
</h1>
</body>
</html>
3)
JSP program to count the no. of views:
<html>
<body
bgcolor=green text=yellow>
<h1><%!
int count=0; %>
This page
has been accessed <%= ++count %> times
</h1>
</body>
</html>
4)
Program to display system time:
<html>
<body
bgcolor=green text=yellow>
<h1>
<%
java.util.Date d=new java.util.Date(); %>
<%=
d.getHours() %>:<%= d.getMinutes() %>:
<%=
d.getSeconds() %>
</h1>
</body>
</html>
5)
Program to display multiplication table:
<html>
<body
bgcolor=red text=yellow>
<table
border=20>
<%
for(int i=1;i<=100;i++) { %>
<tr>
<td> 5
</td>
<td> x
</td>
<td><%=
i %></td>
<td> =
</td>
<td><%=
5*i %></td>
</tr>
<% }
%>
</table>
</body>
</html>
Read More
By
Mr. Venkatesh Mansani
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