Access Java Object from a script

Byron KiourtzoglouNovember 11th, 2012Last Updated: October 4th, 2013

0 71 1 minute read

In this example we shall show you how to access a Java Object from a script. We are using the ScriptEngine interface that provides methods for the basic scripting functionality. To access a Java Object from a script one should perform the following steps:

Create a new ScriptEngineManager. The ScriptEngineManager implements a discovery and instantiation mechanism for ScriptEngine classes and also maintains a collection of key/value pairs storing state shared by all engines created by the Manager.

Use the getEngineByExtension(String extension) API method to look up and create a ScriptEngine for the js extension.

Use put(String key, Object value) API method of ScriptEngine to set a key/value pair in the state of the ScriptEngine that may either create a Java Language Binding to be used in the execution of scripts or be used in some other way, depending on whether the key is reserved. The value set here is a list of String car brands, with the key "brandArray".

Create a new String script to print the elements in the list.

Use the eval(String script) method to execute the script,

as described in the code snippet below.

package com.javacodegeeks.snippets.core;

import javax.script.ScriptEngineManager;
import javax.script.ScriptEngine;
import javax.script.ScriptException;
 
public class AccessJavaObjectFromScript {
    public static void main(String[] args) {

  

  // Create an array of car brands

  String[] brands = {"Audi", "Mercedes", "Renault", "Ford", "Seat"};
 

  // Script that reads the values of the array that contains string of car brands.

  String script =


    "var index; " +


    "var brands = brandsArray; " +


    " " +


    "for (index in brands) { " +


    "    println(brands[index]); " +


    "}" ;
 

  // Obtain a ScriptEngine instance.

  ScriptEngineManager manager = new ScriptEngineManager();

  ScriptEngine engine = manager.getEngineByExtension("js");
 

  // Place the brands array into the engine using brandsArray key.

  engine.put("brandsArray", brands);
 

  try {


engine.eval(script);

  } catch (ScriptException e) {


e.printStackTrace();

  }
    }
}

Output: