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<document>

 <properties>
  <title>Turbine Services - JSON-RPC Service</title>
  <author email="seade@backstagetech.com.au">Scott Eade</author>
 </properties>

<body>

<section name="JSON-RPC Service">

<p>
The JSON-RPC Service supports JavaScript to Java AJAX communications using
<a href="http://oss.metaparadigm.com/jsonrpc/">JSON-RPC-Java</a>.
</p>

</section>

<section name="Configuration">

<source><![CDATA[
# -------------------------------------------------------------------
#
#  S E R V I C E S
#
# -------------------------------------------------------------------
...
services.JsonRpcService.classname=org.apache.turbine.services.jsonrpc.TurbineJsonRpcService
...
]]></source>

</section>

<section name="Usage">

<p>
There are a number of things you need to do in order to add AJAX functionality
to your webapp.  First you implement the functions:
</p>

<source><![CDATA[
public class MyJsonFunctions
{
    private String getHello(String clientParameter)
    {
        return "Hello " + clientParameter;
    }
    private String getGoodbye(String clientParameter)
    {
        return "Goodbye " + clientParameter;
    }
}
]]></source>

<p>
Next you implement your Screen class to make your functions available:
</p>

<source><![CDATA[
public class MyJsonScreen extends JSONScreen
{
    public void doOutput(RunData data) throws Exception
    {
        User user = data.getUser();

        MyJsonFunctions myFunctions = new MyJsonFunctions(user.getName());

        // Session specific
        TurbineJsonRpc.registerObject(data.getSession(), "myFunctions", myFunctions);

        // Global
        //TurbineJsonRpc.registerObjectGlobal("testGlobal", testObject);

        super.doOutput(data);
    }
}
]]></source>

<p>
Now we shift focus to your template classes.  Firstly, there are a few useful
utility functions that you need to make sure are available to the pages that
will include AJAX functionality:
</p>

<source><![CDATA[
// Body onload utility (supports multiple onload functions)
function SafeAddOnload(func) {
	var oldonload = window.onload;
	if (typeof window.onload != 'function') {
		window.onload = func;
	} else {
		window.onload = function() {
			oldonload();
			func();
		};
	}
}

// Prepare for possible JSON-RPC requests.
// jsonurl must be set before calling this function.
function jsonOnLoad() {
	try {
		jsonrpc = new JSONRpcClient(jsonurl);
	}
	catch(e) {
		if(e.message) {
			alert(e.message);
		}
		else {
			alert(e);
		}
	}
}

// Process a JSON-RPC request.
function jsonEval(evalStr) {
	try	{
		return eval(evalStr);
	}
	catch(e) {
		if(e.javaStack) {
			alert("Exception: \n\n" + e.javaStack);
		}
		else {
			alert("Exception: \n\n" + e);
		}
	}
	return null;
}
]]></source>

<p>
In these pages you also need to include the JavaScript necessary to process the
JSON calls - this file is available as part of the JSON-RPC-Java distribution
(it is included in the <code>webapps\jaonrpc</code> directory):
</p>

<source><![CDATA[
$page.addScript($content.getURI('scripts/jsonrpc.js'))
]]></source>

<p>
Then you need to set up the specific handler for the page:
</p>

<source><![CDATA[
<script type="text/javascript">
<!--
  ## Set up the JSON-RPC handler.
  var jsonurl = '$link.setScreen("MyJsonScreen")';
  SafeAddOnload(jsonOnLoad);
  ## myArg below would be provided when you call this function from your
  ## web page (usually you would retrieve something via the DOM or your
  ## favorite JavaScript DOM wrapper library).
  function retrieveHello(myArg) {
    ## This is a synchronous call.
    var helloResult = jsonEval("jsonrpc.myFunctions.getHello(" + myArg + ")");
    if(null == helloResult) {
      alert('Something went wrong!');
      return;
    }
    ## Here you would again use the DOM to include the result somewhere on your
    ## page.
  }
//-->
</script>
]]></source>

<p>
The above code is executable by users that are not logged into your application.
Your Screen class can extend JSONSecureScreen to require that users be logged in
before allowing execution.
</p>

</section>

</body>
</document>