Network Deployment (Distributed operating systems), v8.0 > Develop and deploying applications > Develop SCA composites > Specify bindings in an SCA environment > Use Atom bindings in SCA applications

Use Widget implementation in JavaScript with Atom bindings

The JavaScript code in an HTML file can use Service Component Architecture (SCA) references that are defined in a Tuscany Widget implementation. Use Widget implementation to work with data in Atom collections that an SCA service returns in JavaScript.

We can use an Atom binding in an SCA application to expose collections of data as an Atom feed or to reference existing external Atom feeds. If you are unfamiliar with the Atom protocol, refer to documentation on the Atom Syndication Format, an XML-based document format that describes web feeds, and the Atom Publishing Protocol, a protocol for publishing and updating web resources.

An SCA component can define SCA references for use in JavaScript code. Use Tuscany Widget implementation to define the references. The implementation supports references that use an Atom binding, and does not support the definition of SCA services.

The SCA composite that uses the Widget implementation must be deployed inside a Web application archive (WAR) file.

Procedure

1. Configure a Widget implementation in an SCA composite definition.

   Create an SCA composite definition file for a component that uses Tuscany implementation.widget. For example:

   <composite>
   <component name="Store">     
   <tuscany:implementation.widget location="ui/store.html"/>
   
   <reference name="shoppingCart">         
   <tuscany:binding.atom uri="/ShoppingCart/Cart"/>
   
   </reference>
   </component>
   </composite> 

   This example defines a Store component that uses Tuscany implementation.widget in an HTML file at ui/store.html.

2. Enable the SCA reference in an HTML file.

   In the HTML file, ui/store.html, define two required script elements that enable SCA references. Specify the following for the first element:

   <script type="text/javascript>>      dojo.registerModulePath("tuscany", "/Store/tuscany");
        dojo.require("tuscany.AtomService");
   
   </script> 

   This definition is required when using Atom binding references. The dojo.registerModulePath method tells the dojo object where to find requirements in the Tuscany namespace. The first argument is always "tuscany". The second argument is specified in the format /SCA_component_name/tuscany. The dojo.require statement for "tuscany.AtomService" causes the browser to load the JavaScript file from the /Store/tuscany/AtomService.js file. The product dynamically generates this file to connect the Atom binding references to Atom services.

   Specify the following for the second element:

   <script type="text/javascript" src="/Store/store.js">
   </script> 

   This definition is required in any HTML file used as an implementation for a Widget implementation component. For the script src attribute, specify the uniform resource identifier (URI) in the format /SCA_component_name/modified_implementation.widget_location_attribute; for example, /Store/store.js. The modified location attribute is the Widget implementation location attribute without a leading path and with a file extension of .js.

3. Define the SCA reference in JavaScript in the HTML file.

   An HTML file that contains the above example reference might resemble:

   //@Reference
   var catalog = new tuscany.sca.Reference("shoppingCart");
   

   The //@Reference comment is required. The SCA run time interprets the comment in the same manner that a Java class interprets an @Reference tag.

4. Use JavaScript to manipulate the feed reference.

   For example, to retrieve an entire feed, the HTML file might use the following example code:

   var items = shoppingCart.get("");
   

   To retrieve a single entry, the implementation might call:

   var item = shoppingCart.get("Item1");
   

   To add a new entry to the feed, the HTML file might use the following example code:

   var entry =
     '
   <entry xmlns="http://www.w3.org/2005/Atom">
   <title>item
   </title>
   <content type="text/xml">'
      + '
   <Item xmlns="http://services/">' +
   <name xmlns="">' + itemName + '
   </name>'
      + '
   <price xmlns="">' + itemPrice + '
   </price>' + '
   </Item>' + '
   </content>
   </entry>';
   
   shoppingCart.post(entry);
   

What to do next

Deploy your SCA component in an application.

For additional examples, see the topic on using Widget implementation in JavaScript with Atom or HTTP bindings.
Use Widget implementation in JavaScript with Atom or HTTP bindings
Use Atom bindings in SCA applications
Specify bindings in an SCA environment
Atom Syndication Format
Atom Publishing Protocol

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