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javascriptjavanashornjavascript-engine

ScriptEngine - Calling javascript closure from java


I am trying to invoke a javascript closure from Java using ScriptEngine. See below the code snippet. I removed the script engine eval code for brevity.I was able to invoke the function which has a closure but not the closure, any help is appreciated

//Java code snippet

        ScriptObjectMirror execute = (ScriptObjectMirror) engine.get("transform");
    ScriptObjectMirror closure = (ScriptObjectMirror) execute.callMember("execute", new TestObj());
    for (String s: closure.getOwnKeys(true)) {
        System.out.println(s);
    }

//Javascript code

var transform = {
execute : function(execution) {
    print("hello");execution.setVariable("test","testing");
    function transform(execution) {
        execution.setVariable("result", {result:"myjson object"});
        print("Testing");
    }
    return transform;
}

}

hello
name:test,testing
prototype
length
name

Solution

  • Solved the issue, here is the fully working code

    import jdk.nashorn.api.scripting.ScriptObjectMirror;
    import javax.script.ScriptEngine;
    import javax.script.ScriptEngineManager;
    import javax.script.ScriptException;
    
    public class Main {
    
        public static class TestObj {
    
            public TestObj() {
    
            }
            public void setVariable(String name, Object value) {
                System.out.println(name + ":" + value);
                if (value instanceof ScriptObjectMirror) {
                    ScriptObjectMirror scriptObjectMirror = (ScriptObjectMirror) value;
                    String[] ownKeys = scriptObjectMirror.getOwnKeys(true);
                    for (String k: ownKeys) {
                        System.out.println(scriptObjectMirror.get(k));
                    }
                }
            }
        }
    
        public static void main(String[] args) throws ScriptException {
            System.out.println("Hello World!");
    
    
            ScriptEngineManager scriptEngineManager = new ScriptEngineManager();
            ScriptEngine engine = scriptEngineManager.getEngineByName("javascript");
            String js = "var transform = {\n" +
                    "execute : function(execution) {\n" +
                    "    print(\"hello\");" +
                    "execution.setVariable(\"test\",\"testing\");\n" +
                    "    function transform(execution) {\n" +
                    "        execution.setVariable(\"result\", {result:\"myjson object\"});\n" +
                    "        print(\"Testing\");\n" +
                    "    }\n" +
                    "    return transform;\n" +
                    "}}";
            System.out.println(engine);
            engine.eval(js);
            //engine.put("execution", new TestObj());
            ScriptObjectMirror transform = (ScriptObjectMirror) engine.get("transform");
            ScriptObjectMirror execute = (ScriptObjectMirror) transform.callMember("execute", new TestObj());
            execute.call(execute,new TestObj());
            System.out.println("fully working code");
        }
    }
    

    Output

    Hello World!
    jdk.nashorn.api.scripting.NashornScriptEngine@6d7b4f4c
    hello
    test:testing
    result:[object Object]
    myjson object
    Testing
    fully working code