--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/uidesigner/com.nokia.sdt.uimodel/src/com/nokia/sdt/component/ComponentSystem.java	Fri Apr 03 23:33:03 2009 +0100
@@ -0,0 +1,152 @@
+/*
+* Copyright (c) 2009 Nokia Corporation and/or its subsidiary(-ies).
+* All rights reserved.
+* This component and the accompanying materials are made available
+* under the terms of the License "Eclipse Public License v1.0"
+* which accompanies this distribution, and is available
+* at the URL "http://www.eclipse.org/legal/epl-v10.html".
+*
+* Initial Contributors:
+* Nokia Corporation - initial contribution.
+*
+* Contributors:
+*
+* Description: 
+*
+*/
+/**
+ * 
+ */
+package com.nokia.sdt.component;
+
+import com.nokia.sdt.uimodel.Messages;
+import com.nokia.sdt.uimodel.UIModelPlugin;
+import com.nokia.cpp.internal.api.utils.core.Check;
+import com.nokia.cpp.internal.api.utils.core.Logging;
+
+import org.eclipse.core.runtime.*;
+
+import java.text.MessageFormat;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * The interface for the component system.
+ * 
+ * This maintains a collection of component providers. Each provider
+ * represents a specific implementation of components and
+ * can provide a unique set of IComponent instances.
+ * 
+ * @see IComponent
+ * 
+ * 
+ */
+public class ComponentSystem {
+	
+		/**
+		 * Name of the component provider extension point
+		 */
+	public static final String PROVIDER_EXTENSION = "componentProvider"; //$NON-NLS-1$
+	
+	static private ComponentSystem instance;
+	
+        /**
+         * Map of String -> IComponentProvider
+         */
+	private Map providers = new HashMap();
+	
+		/**
+		 * Returns the singleton instance of the component system
+		 */
+	static public ComponentSystem getComponentSystem() {
+		if (instance == null) {
+			instance = new ComponentSystem();
+		}
+		return instance;
+	}
+	
+	private ComponentSystem() {
+	}
+
+	/**
+	 * Returns the requested component provider implementation, if loaded.
+	 * @param id a string representing the provider
+	 * @return provider or null if not yet loaded
+	 * @throws CoreException
+	 */
+	public synchronized IComponentProvider findProvider(String id) throws CoreException {
+		return (IComponentProvider) providers.get(id);
+	}
+
+	/**
+	 * Returns the requested component provider implementation,
+	 * loading its extension if necessary.
+	 * @param id a string representing the provider
+	 * @return provider or null if not found
+	 * @throws CoreException
+	 */
+	public synchronized IComponentProvider getProvider(String id) throws CoreException {
+			// check if already loaded this provider
+		IComponentProvider result = (IComponentProvider) providers.get(id);
+		if (result == null) {
+	        result = loadExtensions(id);
+	        providers.put(id, result);
+		}
+		return result;
+	}
+
+    /**
+     * Set the component provider
+     * <p>
+     * For testing to set a provider without requiring a running workbench.
+     * @param id a string representing the provider
+     * @param provider the provider instance (must not be null)
+     */
+    public synchronized void setProvider(String id, IComponentProvider provider) {
+        Check.checkArg(id);
+        Check.checkArg(provider);
+        providers.put(id, provider);
+    }
+    
+    private IComponentProvider loadExtensions(String id) throws CoreException {
+        IComponentProvider result = null;
+        
+        // Get implementors of the componentProvider extension point
+        IExtensionRegistry er = Platform.getExtensionRegistry();
+        if (er == null)
+            return null;
+        
+        IExtensionPoint ep = er.getExtensionPoint(
+                UIModelPlugin.PLUGIN_ID, PROVIDER_EXTENSION);
+
+        IExtension matched = null;
+        
+        // Iterate over all providers looking for the requested one
+        IExtension[] extensions = ep.getExtensions();
+        for (int i = 0; i < extensions.length; i++) {
+			IExtension extension = extensions[i];
+			IConfigurationElement[] ces = extension.getConfigurationElements();
+			if (ces != null && ces.length >= 1) {
+				IConfigurationElement providerElement = ces[0];
+				String name = providerElement.getAttribute("name"); //$NON-NLS-1$
+				if (name != null && name.equals(id)) {
+					if (providerElement.getAttribute("class") != null) { //$NON-NLS-1$
+                        if (result != null) {
+                            Logging.log(UIModelPlugin.getDefault(), 
+                                    Logging.newStatus(UIModelPlugin.getDefault(),
+                                            IStatus.ERROR,
+                                            MessageFormat.format(Messages.getString("ComponentSystem.1"),
+                                                    new Object[] { id, extension.getUniqueIdentifier(), matched.getUniqueIdentifier() })
+                                                    
+                                            ));
+                        } else {
+                            result = (IComponentProvider) providerElement.createExecutableExtension("class"); //$NON-NLS-1$
+                            matched = extension;
+                        }
+					}
+				}
+			}
+        }
+        return result;
+    }
+}