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Title: JSP Tag Libraries
ISBN: 193011009X
US Price: $35.96
Publication Date: May 2001
Pages: 656
© 2001 Manning Publications Co.

Reviews : Java Books :
JSP Tag Libraries : Chapter 10: Iterating with Tags

10.4 Look, Mom! No scriptlets— IterateTag in action

Armed with IterateTag we can now greatly improve our JSP development and even reach the point at which scriptlets are no longer needed. To illustrate, we present a real world example wherein a JSP file shows a user the content of his or her shopping cart. For this example, the shopping cart is kept inside a session variable that the JSP file retrieves to create a table containing the current products in the cart.

The methods provided by the shopping cart and the cart items are available in listing 10.12.

Listing 10. 12 The methods exposed by the cart and cart elements 

public class Cart implements Serializable { 
	public int getDollars(); 
	public int getCents(); 
	public boolean isEmpty(); 
	public Enumeration getProducts(); 
	public Enumeration getProductNames(); 
	public CartElement getProduct( String key); 
	public CartElement [] getProductValues(); 
	public void addProduct(String key, CartElement ince); 
	public void removeProduct(String key); 
} 

public class CartElementImp implements CartElement { 
	public int getDollars(); 
	public void setDollars(int dollars); 
	public int getCents(); 
	public void setCents(int cents); 
	public int getQuantity(); 
	public void setQuantity(int quantity); 
	public void setName(String name); 
	public String getName(); 
}

10.4.1 Printing the shopping cart with scriptlets

Assuming we have the cart in the session state and we want to display the cart's content in some tabular format (figure 10.2), we could create a scriptlet-littered JSP file, such as the one seen in listing 10.13.

Listing 10. 13 JSP file that uses scriptlets to present the cart information 

<%@ page errorPage="error.jsp" %> 
<%@ page import="book.util.*,java.util.*" %>  

<html> 
<body> 

<% 
	Cart cart = (Cart) session.getAttribute("cart");  
	if(! cart.isEmpty()) { 
%> 
Your cart contains the following products: 

<table> 
<tr>< th> Product</th> <th> Quantity</th> <th> Price</th> </tr> 
<% java.util.Enumeration e = cart.getProducts(); 
	while( e.hasMoreElements()) { 
		CartElementImp p = (CartElementImp) e.nextElement(); 
%> 
	<tr> 
		<td> <%= p.getName() %></td> 
		<td> <%= p.getQuantity() %> </td> 
		<td> <%= p.getDollars() %>.<%= p.getCents() %>$ </td> 
	</tr> 
<% } %> 
	<tr> 
		<td> Totals <td> 
		<td> <%= cart.getDollars() %>.<%= cart.getCents() %>$< td>  
	<tr> 
</table> 

<% } else { %> 
Your cart is empty. 
<% } %> 

</body> 
</html>

Importing classes to be used in the scriptlets.

Gets a reference to the cart.

Enumerates the products and presents their properties.

Presents the total price (property of the cart).

Listing 10.13 serves as a basic example for a piece of JSP code that, once introduced to the scriptlets, is no longer manageable by anyone but a Java programmer. The file is replete with the familiar Java curly brackets, Java flow control statements, and casting and import statements— all of which are difficult for a non-Java programmer to grasp. Instead of this chaos, we can use the IterateTag we just developed to substantially improve the JSP.

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