What's "JavaScript SOAP Client"?
A lot of talking about AJAX is taking place here and there; AJAX is the acronym of "Asynchronous JavaScript and XML", a technology based on XMLHttpRequest, which is now supported by all main browsers. The basic idea is quite simple - and not actually a breakthrough - but it allows updating a page following a server request, without reloading the entire set of data.
We propose a solution based on AJAX that has a great advantage with respect to those commonly found in Internet: calls are made to the Web Services.
This permits:
- On the server side we only have to expose a Web Service with the required methods (instead of generating dynamic pages incorporating data that are based on a custom syntax or on a generic XML)
- On the client side we use the WSDL (Web Service Description Language) to automatically generate a JavaScript proxy class so as to allow using the Web Service return types - that is similar to what Visual Studio does when a Web Reference is added to the solution.
The following diagram shows the SOAP Client workflow for asynchronous calls:
The Client invokes the SOAPClient.invoke method using a JavaScript function and specifying the following:
- Web Service URL (pls note that many browsers do not allow cross-domain calls for security reasons)
- Web method name
- Web method parameter values
- Call mode (async = true, sync = false)
- CallBack method invoked upon response reception (optional for sync calls)
The SOAPClient.invoke method executes the following operations (numbers refer to the previous diagram)
- It gets the WSDL and caches the description for future requests
- It prepares and sends a SOAP request to the server (invoking method and parameter values)
- It processes the server reply using the WSDL so as to build the corresponding JavaScript objects to be returned
- If the call mode is async, the CallBack method is invoked, otherwise it returns the corresponding object
