CODEWITHSUNDEEP
javascriptjavajava-8nashorn
igr
igr

Reputation: 10604

How to invoke Nashorns `ScriptFunction` callback from Java?

I have some javascript code that is executed onto my object in Java Nashorn:

scriptEngine.eval("my.fn(function(a,b) {...}");

I can create method fn in my class that receives the ScriptFunction, but I don't get how to pass arguments and invoke this function from Java.

EDIT

I can make fn(Runnable) or fn(Callable) but I still don't know how to pass arguments to any of these two, from my Java implementation of fn?

Upvotes: 2

Views: 1513

Answers (1)

A. Sundararajan
A. Sundararajan

Reputation: 4405

Please avoid using any nashorn internal types like jdk.nashorn.internal.runtime.ScriptFunction in your Java code. With jdk9, jigsaw modular access checks prevent accessing such types from user code!

If you do want a callback to be passed to your Java code which is implemented in Nashorn script, there are two approaches:

1) Accept any @FunctionalInterface type in your code (https://docs.oracle.com/javase/8/docs/api/java/util/function/package-summary.html) like Supplier, Consumer, Function etc. Nashorn allows any script function to be passed as argument when a functional interface object is needed in java code. From script, you can pass a script function. On java side, you just invoke just as an interface method (like "get", "accept", "apply" etc. - these are functional methods on Supplier, Consumer, Function respectively)

2) Accept jdk.nashorn.api.scripting.JSObject ( https://docs.oracle.com/javase/8/docs/jdk/api/nashorn/jdk/nashorn/api/scripting/JSObject.html) type argument in your Java code. From script, you can pass a script function as an argument when JSObject is needed in Java call. From Java code, you can invoke "call" method on JSObject [ https://docs.oracle.com/javase/8/docs/jdk/api/nashorn/jdk/nashorn/api/scripting/JSObject.html#call-java.lang.Object-java.lang.Object...- ]

Upvotes: 4

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