JavaScriptInJava

/* *************************** JavaScriptInJava.java *************************** */
package test.test;

import javax.script.Bindings;
import javax.script.Compilable; // Require Java 8 !!!
import javax.script.CompiledScript; // Require Java 8 !!!
import javax.script.Invocable;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
import javax.script.SimpleBindings;

public class JavaScriptInJava {

    public static void main(String[] args) throws ScriptException, NoSuchMethodException {

        ScriptEngineManager manager = new ScriptEngineManager();
        ScriptEngine engine = manager.getEngineByName("JavaScript");

        /* ----------------------------------------------------------------------- */

        // Put (string) param to JavaScript.
        engine.put("testString", "Hello, world!");
        engine.eval("print(testString)");
        // Put (string) param to JavaScript.

        /* ----------------------------------------------------------------------- */

        // Find max number in int array with JavaScript:
        int[] array = { 3, 6, 2, 56, 32, 5, 89, 32 };
        engine.put("arr", array);

        String script =
                  "var largest = arr[0];                "
                + "function maxNumber(arr) {                "
                + "       for (var i = 0; i < arr.length; i++) {    "
                + "               if (largest < arr[i] ) {      "
                + "                       largest = arr[i];     "
                + "               }                 "
                + "       }                     "
                + "       return largest;               "
                + "}                            "
                + "maxNumber(arr);                  ";

        Number result = (Number) engine.eval(script);
        System.out.println("Max=" + result.longValue());
        // Find max number in int array with JavaScript.

        /* ----------------------------------------------------------------------- */

        // Work with Java class from JavaScript:
        String userScript =
                  "user1.setName(\"Test User\");        "
                + "print( user1.getName() );            ";

        Bindings bindings = new SimpleBindings();
        User u = new User();
        bindings.put("user1", u);

        engine.eval(userScript, bindings);

            // Require Java 8 !!!
        // Compile JavaScript (faster):
        if (engine instanceof Compilable) {
            System.out.println(" Compiling...");
            Compilable compEngine = (Compilable) engine;
            CompiledScript cs = compEngine.compile(userScript);
            cs.eval(bindings);
        } else {
            engine.eval(userScript, bindings);
        }
        // Compile JavaScript (faster).
            // Require Java 8 !!!

        // Work with Java class from JavaScript.

        /* ----------------------------------------------------------------------- */

        // Use JavaScript function in Java code:
        String math =
                  "function addition(a, b) {            "
                + "     return a+b;         "
                + "}                        "
                + "                     "
                + "function substraction(a, b) {        "
                + "     return a-b;         "
                + "}                        "
                + "                     ";

        engine.eval(math);

        Invocable inv = (Invocable) engine;

        int a = 10;
        int b = 5;
        System.out.println("A=" + a + " B=" + b);

        Object aPlusB = inv.invokeFunction("addition", a, b);
        System.out.println("A+B = " + aPlusB);

        Object[] inputParams = {
                new Integer(10),
                b
                };
        Object aMinusB = inv.invokeFunction("substraction", inputParams);
        System.out.println("A-B = " + aMinusB);

        int x = (Integer) aPlusB + 1;
        System.out.println("aPlusB + 1 = " + x);

        // Use JavaScript function in Java code.

        /* ----------------------------------------------------------------------- */
    }
}

/* *************************** User.java *************************** */
package test.test;

public class User {

    private String name;

    public User() {
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}