Understanding "Music Without Borders"
The main interface for "Music Without Borders" is the JSP page eshop.jsp (see Code Listing 1). You will notice that this page is almost exclusively a dedicated user interface and does not assume any processing tasks--is an ideal JSP solution. Also, note that another JSP page cart.jsp (see Code Listing 2) is eshop.jsp by the instruction <jsp:include page= "cart.jsp" flush= "true"/> included.
Code Listings 1:eshop.jsp
<%@ page session= "true"%>
<title>music without borders</title>
<body bgcolor= "#33CCFF" >
<font face= "Times New roman,times" size= "+3" >
Music without Borders
</font>
<center>
<form name= "Shoppingform"
action= "/examples/servlet/shoppingservlet"
method= "POST" >
<b>CD:</b>
<select name=cd>
<option>yuan | The Guo Brothers | Our | $14.95</option>
<option>drums of Passion | Babatunde Olatunji | Nigeria | $16.95</option>
<option>kaira | Tounami diabate| Mali | $16.95</option>
<option>the Lion is Loose | Eliades Ochoa | Cuba | $13.95</option>
<option>dance the Devil Away | Outback | Australia | $14.95</option>
<option>record of Changes | Samulnori | Korea | $12.95</option>
<option>djelika | Tounami Diabate | Mali | $14.95</option>
<option>rapture | Nusrat Fateh Ali Khan | Pakistan | $12.95</option>
<option>cesaria Evora | Cesaria Evora | Cape Verde | $16.95</option>
<option>ibuki | Kodo | Japan | $13.95</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>
Code Listings 2:cart.jsp
<%@ page session= "true" import= "java.util.*, shopping. CD "%>
<%
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>ALBUM</b></td>
<td><b>ARTIST</b></td>
<td><b>COUNTRY</b></td>
<td><b>PRICE</b></td>
<td><b>QUANTITY</b></td>
<td></td>
</tr>
<%
for (int index=0; index < buylist.size (); index++) {
cd Anorder = (CD) buylist.elementat (index);
%>
<tr>
<td><b><%= anorder.getalbum ()%></b></td>
<td><b><%= anorder.getartist ()%></b></td>
<td><b><%= anorder.getcountry ()%></b></td>
<td><b><%= Anorder.getprice ()%></b></td>
<td><b><%= anorder.getquantity ()%></b></td>
<td>
<form name= "Deleteform"
action= "/examples/servlet/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= "/examples/servlet/shoppingservlet"
method= "POST" >
<input type= "hidden" name= "action" value= "CHECKOUT" >
<input type= "Submit" Name= "Checkout" value= "Checkout" >
</form>
</center>
<%}%>
Here, cart.jsp manipulates the expression of a web-based shopping cart, and in the MVC system, the shopping cart acts as model.
Observe the script fragment at the beginning of the cart.jsp:
<%
Vector buylist = (vector) session.getvalue ("Shopping.shoppingcart");
if (buylist!= null && (buylist.size () > 0)) {
%>
This script mainly takes out the shopping cart from the session. If the cart is empty or has not been created, it is not displayed; Therefore, when the user accesses the application for the first time, the view presented to him is shown in Figure 3:
Figure 3: Music Without Borders, main view
Picture button text: Put in shopping cart
If the shopping cart is not empty, the selected items are taken out of the cart in turn, as shown in the following script fragment:
<%
for (int index=0; index < buylist.size (); index++) {
cd Anorder = (CD) buylist.elementat (index);
%>
Once the variable describing the item is created, it is embedded in the static HTML template using the JSP expression directly. Figure 4 shows the view after the user puts some items into the cart.
Figure 4: Music without Borders, shopping cart view
Text: Music without Borders: Musical no borders; Quantity: quantity; ALBUM: Record; ARTIST: singer; COUNTRY: country; Price: prices; Delete: remove; Checkout: Checkout.
The important point to note here is that the processing of all the actions implemented in eshop.jsp and cart.jsp is controlled by a single servlet――shoppingservlet.java, as shown in Listing 3:
Code Listings 3:shoppingservlet.java
Import java.util.*;
Import java.io.*;
Import javax.servlet.*;
Import javax.servlet.http.*;
Import shopping. CD;
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 ("http://localhost:8080/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")) {
Have you purchased the same CD before?
Boolean match=false;
CD ACD = GETCD (req);
if (buylist==null) {
Put the first CD in the shopping Cart
Buylist = new Vector (); First Order
Buylist.addelement (ACD);
else {//not the first time to buy
for (int i=0; i< buylist.size (); i++) {
cd cd = (CD) buylist.elementat (i);
if (Cd.getalbum (). Equals (Acd.getalbum ())) {
Cd.setquantity (Cd.getquantity () +acd.getquantity ());
Buylist.setelementat (Cd,i);
Match = true;
}//if name matches end
}//For Loop end
if (!match)
Buylist.addelement (ACD);
}
}
Session.putvalue ("Shopping.shoppingcart", buylist);
String url= "/jsp/shopping/eshop.jsp";
ServletContext sc = Getservletcontext ();
RequestDispatcher rd = sc.getrequestdispatcher (URL);
Rd.forward (req, res);
else if (action.equals ("CHECKOUT")) {
float total = 0;
for (int i=0; i< buylist.size (); i++) {
cd Anorder = (CD) 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= "/jsp/shopping/checkout.jsp";
ServletContext sc = Getservletcontext ();
RequestDispatcher rd = sc.getrequestdispatcher (URL);
Rd.forward (Req,res);
}
}
Private CD Getcd (HttpServletRequest req) {
Imagine how ugly it would be if these were all in a script fragment.
String MYCD = Req.getparameter ("CD");
String qty = req.getparameter ("qty");
StringTokenizer t = new StringTokenizer (MYCD, "|");
String album= T.nexttoken ();
String artist = T.nexttoken ();
String country = T.nexttoken ();
String Price = T.nexttoken ();
Price = Price.replace (' $ ', '). Trim ();
cd cd = new CD ();
Cd.setalbum (album);
Cd.setartist (artist);
Cd.setcountry (country);
Cd.setprice (New Float (Price). Floatvalue ());
Cd.setquantity (New Integer (qty)). Intvalue ());
return CD;
}
}
