Serialization of javascript lambdas

[Sundararajan Athijegannathan]

No, none of the nashorn objects are Serializable and that is by design!
As you've found out, Nashorn objects are too 'tied' to the current
execution state - in which most of the objects are not Serializable.

-Sundar


On 6/27/2016 8:56 PM, Tristan Tarrant wrote:
> Hi all,
>
> I've been playing with Nashorn in combination with the Streams API in
> the context of being able to run functions in a distributed
> environment (i.e. Infinispan's server-side scripting).
>
> In plain Java, a lambda has a SerializedLambda form which basically
> encapsulates all of the coordinates that allow the recreation of a
> MethodHandle on the remote side. This obviously assumes that the
> remote classloader has access to the exact same bytecode.
>
> Nashorn lambdas however do not (or cannot?) have a SerializedLambda
> representation, so I'm looking for an alternative way to identify them.
>
> Consider the following snippet which is a (dumb) example:
>
> map.entrySet().stream().map(function(e) e.getValue())
>
> On the Java side, the map method takes a Function parameter.
> Inspecting the parameter I see that Nashorn has created an adapter
> class at runtime
> (jdk.nashorn.javaadapters.java.util.function.Function) and that the
> apply() method of that class is a BoundMethodHandle$Species_LL.
> Unfortunately there is no reference to the original ScriptFunction,
> which would otherwise allow me to invoke toSource() on it, simply
> serialize that string, send it to the remote node, compile it and
> invoke it.
>
> Inspecting further I've understood that anonymous javascript functions
> get bound to method handles identified by a name in the form of L:x
> where "x" looks like a counter. Compiling the same script on multiple
> nodes, the identifier is consistent, however I've found no way to
> invoke those methodhandles on the remote nodes.
> I've noticed that it's possible to get the ScriptFunction passed as a
> parameter (needsCallee), but I haven't understood how to do that.
>
> So my question is: given a Nashorn Java adapter generated from a
> ScriptFunction, is there a way for me to identify the ScriptFunction
> it originates from and to invoke that same function "by name" on a
> remote node which has the same script ?
>
> Thanks
>
> Tristan
>