I want to use graal js to provide some scripting extension to my application
How can i initialize a new java object on the javascript side?
Context ctx = Context ctx = Context.newBuilder().allowHostAccess(HostAccess.ALL).allowAllAccess(true).build().create();
Value binding = ctx.getBindings("js");
binding.putMember("ArrayList", ArrayList.class);
ctx.eval("js","let list = new ArrayList();list.add(\"1\")");
List list = binding.getMember("list").as(List.class);
assert list.size() == 1;
following code throws exception
Exception in thread "main" TypeError: instantiate on JavaClass[java.util.ArrayList] failed due to: Message not supported.
at <js> :program(Unnamed:1:13-27)
at org.graalvm.polyglot.Context.eval(Context.java:371)
Running graalvm-ce-java11 19.3.2
You need to use Java.type
.
Here is an example taken from https://www.graalvm.org/docs/reference-manual/polyglot/
var array = new (Java.type("int[]"))(4);
array[2] = 42;
console.log(array[2])
Here is a fully runnable example tested with GraalVM 20.0.0
import org.graalvm.polyglot.*;
class M {
public static void main(String[] args) {
try (Context context = Context.newBuilder().allowAllAccess(true).build()) {
java.util.ArrayList v = context.eval("js",
"var ArrayList = Java.type('java.util.ArrayList');" +
"var list = new ArrayList();" +
"list.add(1); list").asHostObject();
System.out.println(v.get(0));
assert v.get(0).equals(1);
}
}
}
Run with
graalvm-ce-java8-20.0.0/bin/javac M.java
graalvm-ce-java8-20.0.0/bin/java -ea M
To get 1
as output.