Invoke Script Function using ScriptEngine

This is an example of invoking a method in the Script using Java. We have to create javax.script.ScriptEngineManager and javax.script.ScriptEngine to invoke the methods. In this example I have created two methods one without parameter and one with two parameters. Once we have created the script engine instances, then we need to get javax.script.Invocable instance which is used for invoking the methods. Method invokeFunction() takes the first parameter as method name and variable arguments as the parameters.

Lets look at the example.

JavaScriptEngineMethodExample.java

package javabeat.net.script;

import javax.script.Invocable;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;

/**
 * Invoke Script Method Example
 *
 * @author Krishna
 *
 */
public class JavaScriptEngineMethodExample {
	public static void main(String[] args) throws ScriptException,
			NoSuchMethodException {
		//Write script with two methods
		String str = "function testFn(){" + "println('hi')}"
				+ "function add(a,b){print('Add Function : ');println(a + b)}";

		//Create ScriptEngineManager
		ScriptEngineManager engineManager = new ScriptEngineManager();

		//Create ScriptEngine
		ScriptEngine engine = engineManager.getEngineByExtension("js");

		//Evaluate script
		engine.eval(str);

		//Create Invocable instance
		Invocable invocable = (Invocable) engine;

		//Invoke the methods without parameter
		invocable.invokeFunction("testFn");

		//Invoke the methods with parameters
		invocable.invokeFunction("add", 10, 20);
	}
}

Output…

hi
Add Function : 30