java qr code reader webcam The role of the server in Java

Encoding QR Code in Java The role of the server

The role of the server
QR Code Drawer In Java
Using Barcode printer for Java Control to generate, create QR image in Java applications.
www.OnBarcode.com
QR Code Reader In Java
Using Barcode scanner for Java Control to read, scan read, scan image in Java applications.
www.OnBarcode.com
an asynchronous request, and assign the response to the innerHTML of a DOM element in the current document. We use that approach in chapter 12 in our XSLT-driven phonebook, so we won t reproduce a full example here.
Creating GS1 128 In Java
Using Barcode creator for Java Control to generate, create GS1 128 image in Java applications.
www.OnBarcode.com
Painting Code 128 In Java
Using Barcode generation for Java Control to generate, create Code 128A image in Java applications.
www.OnBarcode.com
5.4.4 Thinking like a plug-in: script-centric interactions
Print GTIN - 12 In Java
Using Barcode printer for Java Control to generate, create UPC-A Supplement 2 image in Java applications.
www.OnBarcode.com
EAN13 Drawer In Java
Using Barcode generation for Java Control to generate, create UPC - 13 image in Java applications.
www.OnBarcode.com
When we send a JavaScript file from our web server to a browser, and it executes in that browser for us, we are actually doing something quite advanced. If we generate the JavaScript that we are sending from a program, we are setting up an even more complex system. Traditionally, client/server programs communicate data to one another. Communicating executable, mobile code across the network opens up a lot of flexibility. Enterprise-grade network languages such as Java and the .NET stack are only just catching on to the possibilities of mobile code, through technologies such as RMI, Jini, and the .NET Remoting Framework. We lightweight web developers have been doing it for years! As usual, Ajax lets us do a few new interesting things with this capability, so let s see what they are. Overview In a classic web application, a piece of JavaScript and its associated HTML are delivered in a single bundle, and the script is typically authored to work with that particular page. Using Ajax, we can load scripts and pages independently of one another, giving us the possibility of modifying a particular page in a number of different ways, depending on the script that we load. The code that constitutes our client-tier application can effectively be extended at runtime. This introduces both problems and opportunities, as we will see. Figure 5.8 illustrates the basic architecture of a script-centric application. The first advantage of this approach over a content-centric solution is that the network activity is relegated to the background, eliminating visual blinking. The exact nature of the script that we generate will depend on the hooks that we expose in the client tier itself. As with much code generation, success hinges on keeping the generated portion simple and making use of nongenerated library code where possible, either transmitted alongside the generated code or resident in the client application. Either way, this pattern results in relatively tight coupling between the tiers. That is, the code generated by the server requires intimate knowledge of API calls on the client. Two problems emerge. First, changes to the server and client code can unintentionally break them. Good modular design principles can offset this to some extent, by providing a well-defined, well-documented API implementing the Fa ade pattern. The second issue is that the stream of JavaScript is very
Printing PDF 417 In Java
Using Barcode creation for Java Control to generate, create PDF417 image in Java applications.
www.OnBarcode.com
Code11 Printer In Java
Using Barcode printer for Java Control to generate, create USD8 image in Java applications.
www.OnBarcode.com
The details: exchanging data
Make Quick Response Code In C#
Using Barcode drawer for VS .NET Control to generate, create QR image in .NET framework applications.
www.OnBarcode.com
QR Code 2d Barcode Reader In .NET Framework
Using Barcode reader for .NET Control to read, scan read, scan image in .NET applications.
www.OnBarcode.com
Client Server Hidden inner frame
Barcode Drawer In Java
Using Barcode printer for Android Control to generate, create Barcode image in Android applications.
www.OnBarcode.com
Printing Code-128 In Visual Studio .NET
Using Barcode printer for VS .NET Control to generate, create Code 128A image in .NET applications.
www.OnBarcode.com
Title Item Item Item
UCC-128 Creation In Java
Using Barcode maker for Android Control to generate, create GS1 128 image in Android applications.
www.OnBarcode.com
Create Data Matrix ECC200 In None
Using Barcode creator for Font Control to generate, create Data Matrix 2d barcode image in Font applications.
www.OnBarcode.com
1. Request
DataMatrix Printer In Java
Using Barcode maker for BIRT reports Control to generate, create Data Matrix 2d barcode image in BIRT reports applications.
www.OnBarcode.com
GTIN - 13 Creator In None
Using Barcode drawer for Font Control to generate, create EAN-13 Supplement 5 image in Font applications.
www.OnBarcode.com
3. Interpret
Decode Barcode In VB.NET
Using Barcode recognizer for .NET framework Control to read, scan read, scan image in VS .NET applications.
www.OnBarcode.com
Create Quick Response Code In None
Using Barcode printer for Office Excel Control to generate, create QR Code image in Excel applications.
www.OnBarcode.com
2. Response
Barcode Encoder In None
Using Barcode printer for Microsoft Word Control to generate, create Barcode image in Microsoft Word applications.
www.OnBarcode.com
Code39 Drawer In None
Using Barcode creation for Microsoft Excel Control to generate, create USS Code 39 image in Excel applications.
www.OnBarcode.com
var title="ABC"; var items={ "1", "2", "3" } show(title,items);
4. Update visible elements
Figure 5.8 Script-centric architecture in an Ajax application. The client application makes a request to the server for a fragment of JavaScript, which it then interprets. The client app exposes several entry points for generated scripts to hook into, allowing manipulation of the client by the script.
specifically designed for this client, and it is unlikely to be as reusable in other contexts in comparison to, say, a stream of XML. Reusability isn t important in all cases, however. Let s have a look at our planetary info example again. Listing 5.4 shows a simple API for displaying our information windows.
Listing 5.4 showPopup() function and supporting code
var offset=8; function showPopup(name,description){ var win=new ScriptIframePopup (name,description,offset,offset,320,320); offset+=32; } function ScriptIframePopup(name,description,x,y,w,h){ var bod=document.createElement("div"); document.body.appendChild(bod); this.contentDiv=document.createElement("div"); this.contentDiv.className="winContents"; this.contentDiv.innerHTML=description; bod.appendChild(this.contentDiv); this.win=new windows.Window(bod,name,x,y,w,h); }
The role of the server
We define a function showPopup that takes a name and description as argument and constructs a window object for us. Listing 5.5 shows an example script that invokes this function.
Listing 5.5 script_earth.js
var name='earth'; var description="A small blue planet near the outer rim of the galaxy," +"third planet out from a middle-sized sun."; showPopup (name,description);
We simply define the arguments and make a call against the API. Behind the scenes, though, we need to load this script from the server and persuade the browser to execute it. There are two quite different routes that we can take. Let s examine each in turn. Loading scripts into IFrames If we load a JavaScript using an HTML document <script> tag, the script will automatically be executed by the interpreter when it loads. IFrames are the same as any other document in this respect. We can define a showInfo() method to create an IFrame for us, and load the script into it:
function showInfo(event){ var planet=this.id; var scriptUrl="script_"+planet+".html"; var dataframe=document.getElementById('dataframe'); if (!dataframe){ dataframe=document.createElement("iframe"); dataframe.className='dataframe'; dataframe.id='dataframe'; dataframe.src=scriptUrl; document.body.appendChild(dataframe); }else{ dataframe.src=scriptUrl; } }
The DOM manipulation methods that we re using should be familiar by now. If we use an invisible IFrame to load our script, we need only concentrate on generating the script itself, since all other interactions are generated for us. So let s stitch our sample script into an HTML document, as shown in listing 5.6.
Copyright © OnBarcode.com . All rights reserved.