Subj : Re: Calling a compiled script with arguments
To   : redcoat
From : Igor Bukanov
Date : Mon Dec 20 2004 10:55 pm

redcoat wrote:
> I've got everything running, but having problems with new objects being
> created unexpectedly...
> 
> I'm using your code as follows:
> 
> private Scriptable prepareExecScope(Scriptable sharedScope, Handler
> client)
> throws EvaluatorException, JavaScriptException, IllegalAccessException,
> InstantiationException, InvocationTargetException,
> ClassDefinitionException, PropertyException
> {
> Context cx = Context.enter();
> try
> {
> Scriptable scope = cx.newObject(sharedScope);
> 
> scope.setPrototype(sharedScope);
> scope.setParentScope(null);
> 
> ScriptableObject.defineClass(scope, MFPHandler.class);
> Scriptable jsClient = cx.newObject(scope, "MFPClient");
> scope.put("client", scope, jsClient);
> 
> return scope;
> }
> finally
> {
> Context.exit();
> }
> }
> 
> The problem comes when I call the ScriptTest - I am passing in an
> MFPClient object that I have already instantiated, and want to use
> that, with it's member variables, with this particular script
> execution.
> 
> However I see the MFPClient constructor getting called twice more, with
> the ScriptableObject.defineClass, and cx.newObject(scope, "MFPClient")
> calls.  Thus the script calls an object that has none of the member
> variables set.

You should call ScriptableObject.defineClass(scope, MFPHandler.class) 
during initialization of the shared scope so all the object/machinery of 
exposing your object would go to the shared scope. That machinery 
includes MFPClient constructor and MFPClient.prototype object to support 
the standard JS-prototype based inheritance.

It also explains why you got MFPHandler constructor executed twice: the 
first time during ScriptableObject.defineClass call to construct 
prototype object and the second time when you call cx.newObject(scope, 
"MFPClient");

> Is there any way to have the script call an pre-instantiated java
> object, which has particular member variables before the script is run.

Sure, just use direct scripting of Java objects also known as 
LiveConnect and replace

 > ScriptableObject.defineClass(scope, MFPHandler.class);
 > Scriptable jsClient = cx.newObject(scope, "MFPClient");
 > scope.put("client", scope, jsClient);

by something like:

public class Example
{
     int value;
     public int getValue() { return value; }
     public void setValue(int value) { this.value = value; }
     public String printValue(int base) { return Integer.toString(value, 
base); }
}

....

Example example = new Example();
example.value = 100;
scope.put("client", scope, Context.javaToJS(example, scope));

Then your scripts can use
client.value = client.value + 100;
var str = client.printValue(10);
etc..


Regards, Igor

.