Adding scripting to java applications

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Many of our applications require scripting support (allowing users to create scripts to customize workflow within the application). Java provides very straightforward scripting via the┬ájavax.script script-engine library. A simple integration is shown below where a Javascript onSave method provided by the user is called, if available, passing a business-logic object “item”:

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

public class Scripting extends Base {
 private ScriptEngineManager mgr;
 private ScriptEngine engine;
 private Invocable invocable;

 private boolean initialize (String script) {
  mgr = new ScriptEngineManager();
  engine = mgr.getEngineByName("js");
  try {
  } catch (ScriptException e) {
   warn("The script could not be loaded: " + e.getMessage());
   return false;
  invocable = (Invocable)engine;
  return true;

 public void onSave(Item item) {
  try {
   invocable.invokeFunction("onSave", item);
  } catch (ScriptException e) {
   warn("The onSave method of the script caused an error: " + e.getMessage());
  } catch (NoSuchMethodException e) {
   // no onSave method provided by the user - that's OK, just ignore it

Note: the javax.script library supports multiple scripting engines including javascript, python, groovy and java. Javascript was the easiest to get working because the Rhino Javascript engine is included in JDK 6.

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