Saturday, May 24, 2014

Java EE 107 Request Dispatcher Method

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Java EE 107 Request Dispatcher Method
This tutorial is based on http://www.youtube.com/watch?v=8cvdgJ94r5M 
STEPS
1) Run Eclipse.
2) Open The Project “ServletJSPExample”.
3) Edit “ServletExample.java”
3.1) Add getRequestDispatcher method.
3.2) Outcome (getRequestDispatcher)
3.3) Add statement to evaluate if input parameter is empty
3.3) Outcome (Null parameter input check)
3.4) Add New JSP file.
3.5) Type the name “output.jsp”
3.6) Select Template “New JSP File (xhtml)”.
3.7) Insert output statements into <body> element:
3.8) Edit ServletExample.java to forward request/response to output.jsp
3.9) Outcome (complete data entry will get data display)

STEPS

1) Run Eclipse.

2) Open The Project “ServletJSPExample”.

3) Edit “ServletExample.java”

3.1) Add getRequestDispatcher method.

getServletContext().getRequestDispatcher("/index.jsp").forward(request, response);

3.2) Outcome (getRequestDispatcher)

3.3) Add statement to evaluate if input parameter is empty

if (request.getParameter("firstname")==null || request.getParameter("lastname")==null){
getServletContext().getRequestDispatcher("/index.jsp").forward(request, response);
return;
}
Or
if (request.getParameter("firstname").equals="" || request.getParameter("lastname").equals=""){
getServletContext().getRequestDispatcher("/index.jsp").forward(request, response);
return;
}

3.3) Outcome (Null parameter input check)

Empty input will be forwarded to index.jsp
Non-empty input will get the input parameter displayed on screen.

3.4) Add New JSP file.

3.5) Type the name “output.jsp”

3.6) Select Template “New JSP File (xhtml)”.

3.7) Insert output statements into <body> element:

        <h1> Your first and last name is:</h1>
        <%
                String firstName=(String) request.getAttribute("firstname");
                String lastName=(String) request.getAttribute("lastname");
                out.println(firstName + " " + lastName);
        %>

3.8) Edit ServletExample.java to forward request/response to output.jsp

1) Delete the statement “PrintWriter out=response.getWriter();
2) Replace the statement “out.println(firstName + " " + lastName);” with the following codes:
request.setAttribute("firstName", firstName);
request.setAttribute("lastName", lastName);
                getServletContext().getRequestDispatcher("/output.jsp").forward(request,response);

3.9) Outcome (complete data entry will get data display)

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