In this session you will learn: Understand Request Dispatcher JSP For more information, visit: https://www.mindsmapped.com/courses/software-development/java-developer-training-for-beginners/

1. Java/J2EE Programming Training
Request Dispatcher

2. Page 2Classification: Restricted
Agenda
• Understand Request Dispatcher
• JSP

3. Page 3Classification: Restricted

4. Page 4Classification: Restricted
num1
num2
Num1= 10
Num2= 20
sum = 30
response
Public void doGet(HttpServletRequest req,
HttpServletResponse res)
{
String num= req.getParameter(“num1”);
String num2 = req.getParameter(“num2”);
int n1 = Integer.parseInt(“num1”);
int n2= Integer.parseInt(“num2”);
Integer sum= n1 +n2;
req.setAttribute(“sum”,sum);
}

5. Page 6Classification: Restricted
FactorialServlet
num1
num2
Rd.forward(req, resp)
Num1= 10
Num2= 20
Sum = 30
respons
e
Public void doGet(HttpServletRequest
req, HttpServletResponse res)
{
request.setAttribute(“sum”, sum);
RequestDispatcher rd;
rd =
req.getRequestDispatcher(“fact”);
rd.forward(req, res)
}

6. Page 8Classification: Restricted
FactorialServlet
num1
num2
Rd.forward
(req, resp)
Public void
doGet(HttpServletRequest req,
HttpServletResponse res)
{ request.setAttribute(“sum”,
sum);
RequestDispatcher rd;
Rd =
req.getRequestDispatcher(“fa
ct”);
rd.forward(req, res)
}
Num1= 10
Num2= 20
Sum = 30
Response
“sum = “ +
sum
Public void
doGet(HttpServletRequest req,
HttpServletResponse res)
{
String sum =
req.getAttribute(“sum”).toString();
out.println( “sum = “ + sum )
}

7. Page 9Classification: Restricted
FactorialServlet
num1
num2
Rd.forward
(req, resp)
Public void
doGet(HttpServletRequest req,
HttpServletResponse res)
{ request.setAttribute(“sum”,
sum);
RequestDispatcher rd;
Rd =
req.getRequestDispatcher(“fact”
);
rd.forward(req, res)
}
Num1= 10
Num2= 20
Sum = 30
Response
“sum = “ +
sum
Public void
doGet(HttpServletRequest req,
HttpServletResponse res)
{
String sum =
req.getAttribute(“sum”).toString();
out.println( “sum = “ + sum )
}

8. Page 10Classification: Restricted
username
password
valid
Home.jsp Login.jsp

9. Page 11Classification: Restricted
public void doGet(HttpServletRequest req,
HttpServletResponse res)
{
if( valid)
{
RequestDispatcher rd =
req.getRequestDispatcher(“Home.jsp”)
rd.forward(req, res);
}
else
{
req.setAttribute(“error”, “username or
password is invalid”);
RequestDispatcher rd
=req.getRequestDispatcher(“Login.jsp”);
rd.forward(req, res);
}
}
login

10. Page 12Classification: Restricted
public void doGet(HttpServletRequest req,
HttpServletResponse res)
{
if( valid)
{
RequestDispatcher rd =
req.getRequestDispatcher(“Home.jsp”)
rd.forward(req, res);
}
else
{
req.setAttribute(“error”, “username or password
is invalid”);
RequestDispatcher rd
=req.getRequestDispatcher(“Login.jsp”);
rd.forward(req, res);
}
}
Home About
username/pwd
invalid
login

11. Page 13Classification: Restricted
public void doGet(HttpServletRequest req,
HttpServletResponse res)
{
if( valid)
{
RequestDispatcher rd =
req.getRequestDispatcher(“Home.jsp”)
rd.forward(req, res);
}
else
{
req.setAttribute(“error”, “username or password is
invalid”);
RequestDispatcher rd
=req.getRequestDispatcher(“Login.jsp”);
rd.forward(req, res);
}
}
Home About
L
Login.jsp
username/pwd
invalid
${requestScope.e
rror}
login
error=“username/pwd is
invalid

12. Page 14Classification: Restricted
JSP
• Java Server Pages
• used for developing server side response
• to add dynamic functionality to web page
• java code is written inside html
• gets the container support
• Life Cycle methods
• jspInit()
• _jspService
• jspDestroy

13. Page 15Classification: Restricted
Compilation & Execution
• Execution of jsp is done in two phases
• translation
• Web container translates Hello.jsp to _Hello.java
• Converts jsp to servlet
• compilation
• generates Hello.class file
• load the class file
• creates the instance of Hello
• calls init method
• call service method
• calls destroy method.

14. Page 16Classification: Restricted
Hello.jsp->_Hello.java
compiles _Hello.java to
_Hello.class

15. Page 17Classification: Restricted
_jspInit()
_jspServic
e()
_jspServic
e()
_jspServic
e()

16. Page 18Classification: Restricted
_jspInit()
_jspServic
e()
_jspServic
e()
_jspServic
e()
jspDestroy()

17. Page 19Classification: Restricted
Thank You