added extension mechanism

src/helma/extensions/ConfigurationException.java

@@ -0,0 +1,9 @@
+package helma.extensions;
+
+public class ConfigurationException extends RuntimeException {
+
+    public ConfigurationException (String msg) {
+	super (msg);
+    }
+
+}

src/helma/extensions/HelmaExtension.java

@@ -0,0 +1,40 @@
+package helma.extensions;
+
+import helma.framework.core.Application;
+import helma.main.Server;
+import helma.scripting.ScriptingEngine;
+
+/**
+  * Helma extensions have to subclass this. The extensions to be loaded are
+  * defined in <code>server.properties</code> by setting <code>extensions =
+  * packagename.classname, packagename.classname</code>.
+  */
+
+public abstract class HelmaExtension {
+
+	/**
+	  * called by the Server at startup time. should check wheter the needed classes
+	  * are present and throw a ConfigurationException if not.
+	  */
+	public abstract void init (Server server) throws ConfigurationException;
+
+	/**
+	  * called when an Application is started.
+	  */
+	public abstract void applicationStarted (Application app) throws ConfigurationException;
+
+	/**
+	  * called when an Application is stopped.
+	  */
+	public abstract void applicationStopped (Application app);
+
+	/**
+	  * called by the ScriptingEngine when it is initizalized. throws a ConfigurationException
+	  * when this type of ScriptingEngine is not supported.
+	  */
+	public abstract void initScripting (Application app, ScriptingEngine engine) throws ConfigurationException;
+
+	public abstract String getName ();
+
+}
+

src/helma/extensions/demo/DemoExtension.java

@@ -0,0 +1,69 @@
+package helma.extensions.demo;
+
+import helma.extensions.HelmaExtension;
+import helma.extensions.ConfigurationException;
+import helma.framework.core.Application;
+import helma.main.Server;
+import helma.scripting.ScriptingEngine;
+
+// fesi-related stuff:
+import FESI.Data.ESObject;
+import FESI.Data.ESWrapper;
+import FESI.Data.GlobalObject;
+import FESI.Exceptions.EcmaScriptException;
+import FESI.Interpreter.Evaluator;
+import helma.scripting.fesi.FesiEvaluator;
+
+
+/**
+  * a demo extension implementation, to activate this add <code>extensions =
+  * helma.extensions.demo.DemoExtensions</code> to your <code>server.properties</code>.
+  * a new global object <code>demo</code> that wraps helma.main.Server
+  * will be added to the scripting environment.
+  */
+
+public class DemoExtension extends HelmaExtension {
+
+	public void init (Server server) throws ConfigurationException {
+	try {
+		// just a demo with the server class itself (which is always there, obviously)
+	    Class check = Class.forName("helma.main.Server");
+	} catch (ClassNotFoundException e) {
+	    throw new ConfigurationException("helma-library not present in classpath. make sure helma.jar is included. get it from http://www.helma.org/");
+	}
+	}
+
+	public void applicationStarted (Application app) throws ConfigurationException {
+	app.logEvent ("DemoExtension init with app " + app.getName () );
+	}
+
+	public void applicationStopped (Application app) {
+	app.logEvent ("DemoExtension stopped on app " + app.getName () );
+	}
+
+	public void initScripting (Application app, ScriptingEngine engine) throws ConfigurationException {
+	if (engine instanceof FesiEvaluator) {
+	    try {
+	        initFesi (app, engine);
+	        app.logEvent("initScripting DemoExtension with " + app.getName () + " and " + engine.toString() );
+	    } catch (EcmaScriptException ecma) {
+	        throw new ConfigurationException (ecma.getMessage());
+	    }
+	} else {
+	    throw new ConfigurationException ("scripting engine " + engine.toString () + " not supported in DemoExtension");
+	}
+	}
+
+	public String getName () {
+	return "DemoExtension";
+	}
+
+	private void initFesi (Application app, ScriptingEngine engine) throws EcmaScriptException {
+	Evaluator evaluator = ((FesiEvaluator)engine).getEvaluator ();
+    ESObject demo = new ESWrapper(Server.getServer (), evaluator);
+    GlobalObject go = evaluator.getGlobalObject();
+	go.putHiddenProperty ("demo", demo);
+	}
+
+}
+