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javascriptjavanashornscriptengine

How to convert ScriptEngine.eval to Java object

I'm using ScriptEngine to run a Javascript. In my case, the Javascript will always return a boolean. I thought that eval() would return an Object that I can cast, but instead it seems to return a ScriptObjectMirror. toString() returns [Boolean true], so the evaluation is working. How can I convert or cast to a Boolean or boolean?

Here is my code

final ScriptEngineManager manager = new ScriptEngineManager();
final ScriptEngine engine = manager.getEngineByName("javascript");
final Object jsEval = engine.eval(String.format("new Boolean(%s)", jsString));
System.out.printf("*** jsEval: %s %s%n ", jsEval, jsEval.getClass().getName());

Output is

*** jsEval: [Boolean true] jdk.nashorn.api.scripting.ScriptObjectMirror
Solution

  • If you know the type for sure, you can use the to method:

    jsEval.to(Boolean.class)