Comtaste Consulting | Enterprise RIA consulting and development

Among the many Flex Builder 4 new features there is the possibility to import REST web services into ActionScript classes, in the same way that the previous builder allowed to import SOAP web services. It can import from XML as well as from JSON data. This new feature can obviously be used to import into ActionScript any kind of services that dynamically generate XML or JSON content.

For the following example I used the MAX preview version of Flex Builder 4, which has many interesting features and, while not yet complete, will become a very good IDE. The example will use a very simple JSP that returns some XML data, dynamically generated as a response to the client invocation. The JSP has contentType="text/xml;", accepts a numeric parameter length and returns a simple structure, with as many nodes as the length parameter. The service called with length=2 will return:

  <root>
    <content value="0"/>
    <content value="1"/>
  </root>

Now we can go to Flex Builder 4 and open the HTTP Service import dialog, right next to the Web Service one. The wizard will ask for the URL of the remote service and will be able to add the parameters accepted by the service. It is possible to define more operations, their parameters and request methods and also import as many HTTP services as we need. The next step will be the creation of the ActionScript classes, by selected the previously defined operations and configure the return type: the wizard will create all necessary classes and the methods to invoke the service, will hide from the developer the conversion between XML/JSON and ActionScript and provide with a transparent and object oriented set of classes ready to be used.

For the above XML the following classes have been created:
  Content.as - with a value property;
  XMLServiceTest - a class containing all the operations to be invoked on this service.
Both of these classes extend a base class, which contains the generated code, so we can safely modify the extending classes, as only the base ones would be overwritten in case of service changes.

Other interesting features of the new builder allow us to rapidly test the newly created services or even to enable paging and data management. By selecting a generated operation and the main application file we can have the builder generate a test datagrid and also all required events for it to work:

  <DataGrid id="DataGrid1" dataProvider="{result1.lastResult}">
    <columns>
      <DataGridColumn headerText="value" dataField="value"/>
    </columns>
  </DataGrid>

With a few clicks we have an application that exchanges strong typed data with a remote server, on top of XML/JSON.

By allowing a transparent conversion between XML/JSON data and ActionScript classes, this HTTP Service import feature makes the development easier for enterprise applications that use REST services or plain XML or JSON as a means of communication.