Script Engine Access

Script Engine Access provides methods for finding and loading scripts from bundles or the default scripts directory.

Overview

Script Engine Access is one of the helper objects available to all scripts that are executed through the OSGiScriptEngine and created by the OSGiScriptEngineManager. It is available to scripts through the Core.getEngine() field and can be accessed in most script languages simply as "mbs.engine".

The Script Engine Access provides methods for finding and loading scripts from bundles or the default scripts directory.

Find Script

The findScript methods can be used to find a script URL by its path. There are two findScript methods:

• URL findScript(String scriptPath) – this method first searches the owning bundle (the bundle used when instantiating the OSGiScriptEngine) for a script with the given path. If one is found its URL is returned. If a script with the given path is not found in the bundle, the default scripts directory is searched. If a script with the given path is found there, its URL is returned, otherwise – a FileNotFoundException is thrown;
• URL findScript(String scriptPath, String bundleSymbolicName) – this method is similar, but only searches for a script with the given path in bundle(s) with the given symbolic name. If a script with the given path is not found in the specified bundle(s) a FileNotFoundException is thrown.

The default scripts directory is defined in the configuration of Scripting Core Bundle. It is ../../../scripts by default.

The URL returned by the findScript methods can be used with methods provided by the language for loading scripts (for example the load method in Nashorn Script Engine, the JavaScript engine which comes with Java 1.8+):

myImportUrl = mbs.engine.findScript("lib/myLib.js")
load(myLibUrl)

thirdPartyLibUrl = mbs.engine.findScript("lib.js", "third.party.bundle")
load(thirdPartyLibUrl )

Load Script

The loadScript methods can be used to find and execute a script from a given bundle (or from the default scripts directory) – effectively loading/importing the script in the engine state. They use the corresponding findScript methods to obtain the script URL and then the OSGiScriptEngine, evaluating the current script is used to execute the found script.

There are two loadScript methods:

• one is taking a single scriptPath parameter (and using the single argument findScript method);
• the other is taking scriptPath and bundleSymbolicName (and using the corresponding two argument findScript method):

  mbs.engine.load("scripts/lib/digits.js");  //load script file from "my"  bundle
  mbs.engine.load("scripts/lib/median.js", "com.prosyst.mbs.scripting.engine.access-demo")  //load script file from bundle with given symbolic name
  
  var digits = randomDigits(7);  //randomDigits is function from digits.js
  var median = median(digits);  //median is function from median.js
  
  print("The median of " + digits + " is " + median);

The Script Engine Access Demo shows how loadScipt methods can be used.