Week 13:
Aim : Write a program to implement
MVC architecture.
Description :
Model-View-Controller
(MVC) is a
classic design pattern often used by applications that need the ability to
maintain multiple views of the same data. The MVC pattern hinges on a clean
separation of objects into one of three categories — models for
maintaining data, views for displaying all or a portion
of the data, and controllers for handling events that
affect the model or view(s).
Because of this separation, multiple views
and controllers can interface with the same model. Even new types of views and
controllers that never existed before can interface with a model without
forcing a change in the model design.
How It Works
The
MVC abstraction can be graphically represented as follows.
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Events typically cause a controller to change
a model, or view, or both. Whenever a controller changes a model’s data or
properties, all dependent views are automatically updated. Similarly, whenever
a controller changes a view, for example, by revealing areas that were
previously hidden, the view gets data from the underlying model to refresh
itself.
A
Concrete Example
We explain the MVC pattern with the help of a
simple spinner component which consists of a text
field and two arrow buttons that can be used to increment or decrement a
numeric value shown in the text field. We currently do not have an element type
that can directly represent a spinner component, but it easy is to synthesize a spinner
using existing element types.
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The spinner’s data is held in a model that is shared with the text field. The
text field provides a view of the spinner’s
current value. Each button in the spinner is an event
source, that spawns an action event every
time it is clicked. The buttons can be hooked up to trampolines
that receive action events, and route them to an action
listener that eventually handles that event. Recall that a trampoline is
a predefined action listener that simply delegates action handling to another
listener.
Depending on the source of the event, the
ultimate action listener either increments or decrements the value held in the
model — The action listener is an example of a controller.
The trampolines that initially receive the
action events fired by the arrow buttons, are also controllers — However,
instead of modifying the spinner’s model directly, they delegate the task to a
separate controller (action listener).
Multiple
Controllers
The MVC pattern allows any number of
controllers to modify the same model. While we have so far focused only on the
two arrow buttons as likely source of events, there is, in fact, a third event
source in this example — Whenever the text field has focus, hitting the enter key fires off an action event that may potentially
be handled by a different action listener than the one handling action events
from the buttons.
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| http://wikibrand.blogspot.in |
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| http://wikibrand.blogspot.in |
Program
:
Eshop.jsp:
<%@ page session="true" %>
<html>
<head>
<title>BOOK STORE</title>
</head>
<body bgcolor="#33CCFF">
<font
face="Times New Roman,Times" size="+3">
BOOK STORE
</font>
<hr><p>
<center>
<form
name="shoppingForm"
action="ShoppingServlet"
method="POST">
<b>BOOK:</b>
<select
name=BOOK>
<option>
10588 | Hans Bergsten | Java Server Pages | O'Reilly | 2 | 34.95</option>
<option>
10589 | Deitel | Internet |McGraw Hill | 4 | 44.95</option>
<option>
10590 | Winston | XML BIBLE |Wiley | 2 | 14.95</option>
</select>
<b>Quantity: </b><input
type="text" name="qty" SIZE="3" value=1>
<input
type="hidden" name="action" value="ADD">
<input
type="submit" name="Submit" value="Add to
Cart">
</form>
</center>
<p>
<jsp:include
page="Cart.jsp" flush="true" />
</body>
</html>
Cart.jsp:
<%@ page session="true"
import="java.util.*, shopping.BOOK" %>
<%
Vector buylist
= (Vector) session.getValue("shopping.shoppingcart");
if (buylist !=
null && (buylist.size() > 0)) {
%>
<center>
<table border="0"
cellpadding="0" width="100%"
bgcolor="#FFFFFF">
<tr>
<td><b>ISBN</b></td>
<td><b>AUTHOR</b></td>
<td><b>TITLE</b></td>
<td><b>PUBLISHER</b></td>
<td><b>EDITION</b></td>
<td><b>PRICE</b></td>
<td><b>QUANTITY</b></td>
<td></td>
</tr>
<%
for (int
index=0; index < buylist.size();index++) {
BOOK anOrder
= (BOOK) buylist.elementAt(index);
%>
<tr>
<td><b><%= anOrder.getisbn() %></b></td>
<td><b><%= anOrder.getAuthor()
%></b></td>
<td><b><%= anOrder.getTitle()
%></b></td>
<td><b><%=
anOrder.getPublisher() %></b></td>
<td><b><%= anOrder.getEdition()
%></b></td>
<td><b><%= anOrder.getPrice() %></b></td>
<td><b><%= anOrder.getQuantity()
%></b></td>
<td>
<form
name="deleteForm"
action="ShoppingServlet"
method="POST">
<input
type="submit" value="Delete">
<input
type="hidden" name= "delindex" value='<%= index
%>'>
<input
type="hidden" name="action" value="DELETE">
</form>
</td>
</tr>
<% }
%>
</table>
<p>
<form name="checkoutForm"
action="ShoppingServlet"
method="POST">
<input
type="hidden" name="action" value="CHECKOUT">
<input
type="submit" name="Checkout"
value="Checkout">
</form>
</center>
<% } %>
Checkout.jsp:
<%@ page session="true" import="java.util.*,
shopping.BOOK" %>
<html>
<head>
<title>BOOK STORE</title>
</head>
<body bgcolor="#33CCFF">
<font
face="Times New Roman,Times" size=+3>
BOOK STORE
CHECK OUT
</font>
<hr><p>
<center>
<table
border="0" cellpadding="0" width="100%" bgcolor="#FFFFFF">
<tr>
<td><b>ISBN</b></td>
<td><b>AUTHOR</b></td>
<td><b>TITLE</b></td>
<td><b>PUBLISHER</b></td>
<td><b>EDITION</b></td>
<td><b>PRICE</b></td>
<td><b>QUANTITY</b></td>
<td></td>
</tr>
<%
Vector buylist
= (Vector) session.getValue("shopping.shoppingcart");
String amount
= (String) request.getAttribute("amount");
for (int i=0;
i < buylist.size();i++) {
BOOK anOrder
= (BOOK) buylist.elementAt(i);
%>
<tr>
<td><b><%= anOrder.getisbn()
%></b></td>
<td><b><%= anOrder.getAuthor() %></b></td>
<td><b><%= anOrder.getTitle()
%></b></td>
<td><b><%=
anOrder.getPublisher() %></b></td>
<td><b><%= anOrder.getEdition()
%></b></td>
<td><b><%= anOrder.getPrice()
%></b></td>
<td><b><%=
anOrder.getQuantity() %></b></td>
</tr>
<%
}
session.invalidate();
%>
<tr>
<td> </td>
<td> </td>
<td><b>TOTAL</b></td>
<td><b>$<%= amount
%></b></td>
<td> </td>
</tr>
</table>
<p>
<a
href="Eshop.jsp">Shop some more!</a>
</center>
</body>
</html>
Error.html:
<html>
<body>
<h1>
Sorry, there was an unrecoverable error!
<br>
Please try <a
href="/examples/jsp/shopping/EShop.jsp">again</a>.
</h1>
</body>
</html>
OUTPUT:
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| http://wikibrand.blogspot.in |
Web.xml:
<web-app>
<servlet>
<servlet-name>ShoppingServlet</servlet-name>
<servlet-class>ShoppingServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>ShoppingServlet</servlet-name>
<url-pattern>/ShoppingServlet</url-pattern>
</servlet-mapping>
</web-app>
ShoppingServlet.java:
import java.util.*;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import shopping.BOOK;
public class ShoppingServlet extends HttpServlet {
public void
init(ServletConfig conf) throws ServletException {
super.init(conf);
}
public void
doPost (HttpServletRequest req, HttpServletResponse res)
throws
ServletException, IOException {
HttpSession
session = req.getSession(false);
if (session
== null) {
res.sendRedirect("/error.html");
}
Vector
buylist=(Vector)session.getValue("shopping.shoppingcart");
String
action = req.getParameter("action");
if
(!action.equals("CHECKOUT")) {
if
(action.equals("DELETE")) {
String del =
req.getParameter("delindex");
int d =
(new Integer(del)).intValue();
buylist.removeElementAt(d);
} else if
(action.equals("ADD")) {
boolean
match=false;
BOOK aCD
= getBOOK(req);
if
(buylist==null) {
buylist = new Vector(); //first order
buylist.addElement(aCD);
} else {
// not first buy
for
(int i=0; i< buylist.size(); i++) {
BOOK
cd = (BOOK) buylist.elementAt(i);
if
(cd.getTitle().equals(aCD.getTitle())) {
cd.setQuantity(cd.getQuantity()+aCD.getQuantity());
buylist.setElementAt(cd,i);
match = true;
}
//end of if name matches
} //
end of for
if
(!match)
buylist.addElement(aCD);
}
}
session.putValue("shopping.shoppingcart", buylist);
String
url="/Eshop.jsp";
//
ServletContext sc = getServletContext();
RequestDispatcher rd = req.getRequestDispatcher(url);
rd.forward(req, res);
}
else
if (action.equals("CHECKOUT"))
{
float
total =0;
for (int
i=0; i< buylist.size();i++) {
BOOK
anOrder = (BOOK) buylist.elementAt(i);
float
price= anOrder.getPrice();
int qty
= anOrder.getQuantity();
total +=
(price * qty);
}
total +=
0.005;
String
amount = new Float(total).toString();
int n =
amount.indexOf('.');
amount =
amount.substring(0,n+3);
req.setAttribute("amount",amount);
String
url="/Checkout.jsp";
ServletContext sc = getServletContext();
RequestDispatcher rd = sc.getRequestDispatcher(url);
rd.forward(req,res);
}
}
private BOOK
getBOOK(HttpServletRequest req) {
String
myBOOK = req.getParameter("BOOK");
String qty =
req.getParameter("qty");
StringTokenizer t = new StringTokenizer(myBOOK,"|");
String isbn=
t.nextToken();
String author= t.nextToken();
String title
= t.nextToken();
String
publisher = t.nextToken();
String
Edition = t.nextToken();
String price
= t.nextToken();
price =
price.replace('$',' ').trim();
BOOK book =
new BOOK();
book.setisbn(isbn);
book.setAuthor(author);
book.setTitle(title);
book.setPublisher(publisher);
book.setEdition(Edition);
book.setPrice((new Float(price)).floatValue());
book.setQuantity((new Integer(qty)).intValue());
return book;
}
}
book.java:
package shopping;
public class BOOK {
String isbn;
String author;
String title;
String publisher;
String Edition;
float price;
int quantity;
public BOOK() {
isbn="";
author="";
title="";
publisher="";
Edition="";
price=0;
quantity=0;
}
public void setPublisher(String
title1) {
publisher=title1;
}
public String getPublisher() {
return publisher;
}
public void setEdition(String
group1) {
Edition=group1;
}
public String getEdition() {
return Edition;
}
public void setisbn(String
title) {
isbn=title;
}
public String getisbn() {
return isbn;
}
public void setAuthor(String
group) {
author=group;
}
public String getAuthor() {
return author;
}
public void setTitle(String cty)
{
title=cty;
}
public String getTitle() {
return title;
}
public void setPrice(float p) {
price=p;
}
public float getPrice() {
return price;
}
public void setQuantity(int q) {
quantity=q;
}
public int getQuantity() {
return quantity;
}
}
OUTPUT:
 |
| http://wikibrand.blogspot.in |
 |
| http://wikibrand.blogspot.in |
RESULT:
Thus the cart page is
dynamited with HTTP sessions and useBean
concept.
SOURCE:PVPSIT FOR JNTU
Nice Blog...Thank You For Sharing This Information..
ReplyDeleteProvident Kenworth
Vaswani Menlo Park
Marina Skies