Package tigase.osgi

Class OSGiScriptEngineManager

java.lang.Object
javax.script.ScriptEngineManager
tigase.osgi.OSGiScriptEngineManager
public class OSGiScriptEngineManager extends ScriptEngineManager
This class acts as a delegate for all the available ScriptEngineManagers. Unluckily, the standard did not define it as an interface, so we need to extend it to allow polymorphism. However, no calls to super are used. It wraps all available ScriptEngineManagers in the OSGi ServicePlatform into a merged ScriptEngineManager.
Internally, what this class does is creating ScriptEngineManagers for each bundle that contains a ScriptEngineFactory and includes a META-INF/services/javax.script.ScriptEngineFactory file. It assumes that the file contains a list of ScriptEngineFactory classes. For each bundle, it creates a ScriptEngineManager, then merges them. @link ScriptEngineFactory objects are wrapped into @link OSGiScriptEngineFactory objects to deal with problems of context class loader: Those scripting engines that rely on the ContextClassloader for finding resources need to use this wrapper and the @link OSGiScriptFactory. Mainly, jruby does.
Note that even if no context classloader issues arose, it would still be needed to search manually for the factories and either use them directly (losing the mimeType/extension/shortName mechanisms for finding engines or manually registering them) or still use this class, which would be smarter. In the latter case, it would only be needed to remove the hack that temporarily sets the context classloader to the appropriate, bundle-related, class loader.
Caveats:
  • All factories are wrapped with an OSGiScriptEngineFactory. As Engines are not wrapped, calls like ScriptEngineManager osgiManager=new OSGiScriptEngineManager(context);
    ScriptEngine engine=osgiManager.getEngineByName("ruby"); ScriptEngineFactory factory=engine.getFactory() //this does not return the OSGiFactory wrapper factory.getScriptEngine(); //this might fail, as it does not use OSGiScriptEngineFactory wrapper     might result in unexpected errors. Future versions may wrap the ScriptEngine with a OSGiScriptEngine to solve this issue, but for the moment it is not needed.