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7-1. IMPLEMENTING AN AJAX SHOPPING CART in Font
CHAPTER 7 7-1. IMPLEMENTING AN AJAX SHOPPING CART Code 39 Extended Encoder In None Using Barcode generator for Font Control to generate, create Code 39 image in Font applications. www.OnBarcode.comGenerate ECC200 In None Using Barcode creator for Font Control to generate, create Data Matrix image in Font applications. www.OnBarcode.comThe class UniqueURL is a single-purpose class, only in that you use it to retrieve the unique URL based on what is defined as the action URL. UniqueURL is instantiated, and the constructor requires you to define the action URL that is then assigned to the data member baseURL. You could call two methods to retrieve the unique URL: getIt and postIt. Both methods serve the same purpose, except getIt uses the HTTP GET verb, and postIt uses the HTTP POST verb. Internally, the Asynchronous methods are used to make the GET or POST requests. The methods would execute the action URL using either get or post methods and then await a response in the onComplete method. Because UniqueURL is only interested in a redirection, the onComplete method only processes HTTP status code 201. Every other status code is ignored. When the 201 status code is received, the method getResponseHeader retrieves the HTTP header location, as it contains the unique URL. Once the unique URL has been retrieved, the user-implemented method haveIt is called, indicating that a unique URL has been generated. The implementation of UniqueURL is simple and only does one thing, which is convert an action URL into a unique URL. How the server generates the unique URL depends on how the consumer of UniqueURL called the server. In the case of the shopping cart example, all that is required is calling the method getIt. In the case of the bank account, the postIt method with appropriate data is called. Barcode Maker In None Using Barcode creation for Font Control to generate, create Barcode image in Font applications. www.OnBarcode.comPDF417 Encoder In None Using Barcode printer for Font Control to generate, create PDF 417 image in Font applications. www.OnBarcode.comImplementing a Shopping Cart
GTIN - 12 Creation In None Using Barcode generator for Font Control to generate, create UPC-A image in Font applications. www.OnBarcode.comPaint Code 39 Full ASCII In None Using Barcode drawer for Font Control to generate, create Code39 image in Font applications. www.OnBarcode.comThe shopping cart example will be implemented in abbreviated form for explanation purposes. The solution will focus on the generation of the unique URL and using that unique URL when buying something. The Initial Solution The following illustrates the shopping example source code. Source: /client/ajaxrestrecipes/architecture/shoppingcart.html <html> <head> <title>Shopping cart</title> <script language="JavaScript" src="/scripts/jaxson/common.js"></script> <script language="JavaScript" src="/scripts/jaxson/communications.js"></script> </head> <script type="text/javascript"> var unique = new UniqueURL( "/pyservices/shopping/cart/getone"); unique.haveIt = function() { document.getElementById( "status").innerHTML = "Have shopping cart"; } function Initialize() { unique.getIt(); } Draw EAN13 In None Using Barcode creation for Font Control to generate, create GTIN - 13 image in Font applications. www.OnBarcode.comPainting Codabar In None Using Barcode maker for Font Control to generate, create NW-7 image in Font applications. www.OnBarcode.comCHAPTER 7 7-1. IMPLEMENTING AN AJAX SHOPPING CART
Code 39 Full ASCII Creator In None Using Barcode creator for Online Control to generate, create Code 39 image in Online applications. www.OnBarcode.comCode 3 Of 9 Decoder In None Using Barcode decoder for Software Control to read, scan read, scan image in Software applications. www.OnBarcode.comfunction CustomerDetails() { var obj = new Object(); obj.data = "address=..."; obj.length = obj.data.length; obj.mimetype = "application/x-www-form-urlencoded"; return obj; } function BuyItems() { if( unique.uniqueURL != null) { var asynchronous = FactoryHttp.getAsynchronous(); asynchronous.settings = { onComplete : function(xmlhttp) { // Process the data ... unique.uniqueURL = null; unique.getIt(); } } asynchronous.post( unique.uniqueURL + "/checkout", CustomerDetails()); } } </script> <body onload="Initialize()"> <input type="button" value="Buy it" onclick="BuyItems()" /> <div id="status"></div> <div id="error"></div> </body> </html> In the source code example, the bold code represents the pieces of functionality that relate to a specific use of UniqueURL. The HTML page in an overall context represents the parent page that everyone uses to get a shopping cart and buy some items. When the page is loaded, the body.onload event is triggered, causing the Initialize function to be called. In the implementation of Initialize, unique.getIt is called, which results in a unique URL that represents a shopping cart. By adding the unique URL code to the body.onload event, you re assured that whoever visits the HTML page will have a shopping cart at their disposal. The generated URL is used whenever users click on the Buy It button, triggering the function called BuyItems. The general implementation of BuyIt is not important, because what you re doing is posting the last remaining details to buy whatever users have added to the shopping cart. In the asynchronous.post method call, the URL used is unique.uniqueURL. When the purchase has cleared in the onComplete implementation, the uniqueURL data member is cleared and a new, unique shopping-cart URL is retrieved. EAN / UCC - 14 Printer In Objective-C Using Barcode drawer for iPad Control to generate, create UCC-128 image in iPad applications. www.OnBarcode.comBarcode Creation In C#.NET Using Barcode creation for .NET framework Control to generate, create Barcode image in VS .NET applications. www.OnBarcode.comCHAPTER 7 7-1. IMPLEMENTING AN AJAX SHOPPING CART
UPC Code Encoder In None Using Barcode generator for Software Control to generate, create UPC A image in Software applications. www.OnBarcode.comBarcode Encoder In None Using Barcode maker for Microsoft Excel Control to generate, create Barcode image in Office Excel applications. www.OnBarcode.comThe code provides an understanding of how to use the unique URL, but you must understand the following considerations: When a unique URL, such as /pyservices/shopping/cart/122343, is returned, the client appends the identifier /checkout. Using a nonappended URL would require the URL to accept POST and GET requests for multiple data structures, and that would be non-REST compliant. On the client side, appending an identifier is not a big deal, but on the server, it does become a big deal, as will be discussed shortly. The example HTML page doesn t include the code to search, browse, and add items to the HTML page. You could use two solutions: content injection or an iframe. Using content injection, the catalog items would be pieces of HTML code that would be added to the current HTML page using the innerHTML property. The other approach is to use a floating iframe, which allows you to separate the display of the catalog items from the manipulation. In the case of the shopping cart, the owner of the unique URL is the client. This raises the question, If the users press the page refresh, how will they remember what they were referencing The server won t tell the clients what the unique URL is. The clients can manage this using client-side cookies, as will be illustrated shortly. Keeping Track of Unique URLs Typically, Web application frameworks use cookies to keep server-side session objects. While it might seem that server-side session objects solve many problems, they in fact can cause many problems. Let s say you re writing a service-oriented architecture (SOA) client that uses Web services nowhere in the Web service documentation will you ever find instructions on how to keep session, because that s how code is written. Remove the term Web service and use a remote procedure call. By default, a remote procedure call won t remember who called it. Remote procedure calls expect the caller to remember that, as that is the right approach. To give you a real-life example of why it s bad to use server-side sessions, let s say you re shopping on Amazon.com, and you decide to purchase some things. You re not going to pay for the contents in your shopping cart, because your mother has decided to purchase everything as a birthday present. In a real-life grocery store, having your mother purchase the contents of your shopping cart is as easy as handing her the shopping cart. Yet at Amazon.com, it is not possible, because the shopping cart is associated with the user as a session object on the server side, as Figure 7-3 illustrates. Generate Code 128 Code Set A In .NET Using Barcode encoder for Reporting Service Control to generate, create Code 128C image in Reporting Service applications. www.OnBarcode.comPrinting ECC200 In Visual Studio .NET Using Barcode generation for VS .NET Control to generate, create DataMatrix image in Visual Studio .NET applications. www.OnBarcode.comQR Encoder In Visual Basic .NET Using Barcode creation for .NET Control to generate, create QR image in Visual Studio .NET applications. www.OnBarcode.comCode 128 Generator In Java Using Barcode printer for Android Control to generate, create Code 128B image in Android applications. www.OnBarcode.comEAN-13 Supplement 5 Printer In None Using Barcode printer for Online Control to generate, create EAN / UCC - 13 image in Online applications. www.OnBarcode.comCode128 Drawer In C#.NET Using Barcode maker for .NET framework Control to generate, create ANSI/AIM Code 128 image in .NET applications. www.OnBarcode.com |
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