Is this possible for use javascript to call a java method?

Question

The java have a script manager that allow java calling javascript, like this:

import javax.script.*;
public class ExecuteScript {
 public static void main(St         


        

Answer 1

Here is a tiny example with Java 8 Nashorn that works as a stand-alone script without any packages:

import javax.script.*;
import java.util.LinkedList;

public class RunJavaFromJs {
  public static void main(String[] args) throws Exception {
    LinkedList jList = new LinkedList<>();
    jList.add((Integer)42);

    ScriptEngine engine = 
      (new ScriptEngineManager())
      .getEngineByName("nashorn");
    Bindings bindings = engine.getBindings(ScriptContext.ENGINE_SCOPE);
    bindings.put("jList", jList);
    engine.eval("" + 
      "load('nashorn:mozilla_compat.js');\n" +
      "// call static method\n" + 
      "var i = Packages.RunJavaFromJs.helloWorld(42);\n" + 
      "// perform side effect\n" + 
      "print('Result was: ' + i + '(printed from JS)');\n" + 
      "// call method on `jList` instance passed in bindings \n" +
      "jList.add(12345);\n" +
      "print(jList.toString());"
    );
  }
  public static int helloWorld(int x) {
    System.out.println("Hello, world! (printed from Java in static method)");
    return x * x;
  }
}

If you just save it in RunJavaFromJs.java, then compile and run using

javac RunJavaFromJs.java && java RunJavaFromJs

then you obtain:

Hello, world! (printed from Java in static method)
Result was: 1764(printed from JS)
[42, 12345]