1 /*

     2 * Copyright (c) 2009 Nokia Corporation and/or its subsidiary(-ies).

     3 * All rights reserved.

     4 * This component and the accompanying materials are made available

     5 * under the terms of the License "Eclipse Public License v1.0"

     6 * which accompanies this distribution, and is available

     7 * at the URL "http://www.eclipse.org/legal/epl-v10.html".

     8 *

     9 * Initial Contributors:

    10 * Nokia Corporation - initial contribution.

    11 *

    12 * Contributors:

    13 *

    14 * Description: 

    15 *

    16 */

    17 /**

    18  * 

    19  */

    20 package com.nokia.sdt.component;

    21 

    22 import com.nokia.sdt.uimodel.Messages;

    23 import com.nokia.sdt.uimodel.UIModelPlugin;

    24 import com.nokia.cpp.internal.api.utils.core.Check;

    25 import com.nokia.cpp.internal.api.utils.core.Logging;

    26 

    27 import org.eclipse.core.runtime.*;

    28 

    29 import java.text.MessageFormat;

    30 import java.util.HashMap;

    31 import java.util.Map;

    32 

    33 /**

    34  * The interface for the component system.

    35  * 

    36  * This maintains a collection of component providers. Each provider

    37  * represents a specific implementation of components and

    38  * can provide a unique set of IComponent instances.

    39  * 

    40  * @see IComponent

    41  * 

    42  * 

    43  */

    44 public class ComponentSystem {

    45 	

    46 		/**

    47 		 * Name of the component provider extension point

    48 		 */

    49 	public static final String PROVIDER_EXTENSION = "componentProvider"; //$NON-NLS-1$

    50 	

    51 	static private ComponentSystem instance;

    52 	

    53         /**

    54          * Map of String -> IComponentProvider

    55          */

    56 	private Map providers = new HashMap();

    57 	

    58 		/**

    59 		 * Returns the singleton instance of the component system

    60 		 */

    61 	static public ComponentSystem getComponentSystem() {

    62 		if (instance == null) {

    63 			instance = new ComponentSystem();

    64 		}

    65 		return instance;

    66 	}

    67 	

    68 	private ComponentSystem() {

    69 	}

    70 

    71 	/**

    72 	 * Returns the requested component provider implementation, if loaded.

    73 	 * @param id a string representing the provider

    74 	 * @return provider or null if not yet loaded

    75 	 * @throws CoreException

    76 	 */

    77 	public synchronized IComponentProvider findProvider(String id) throws CoreException {

    78 		return (IComponentProvider) providers.get(id);

    79 	}

    80 

    81 	/**

    82 	 * Returns the requested component provider implementation,

    83 	 * loading its extension if necessary.

    84 	 * @param id a string representing the provider

    85 	 * @return provider or null if not found

    86 	 * @throws CoreException

    87 	 */

    88 	public synchronized IComponentProvider getProvider(String id) throws CoreException {

    89 			// check if already loaded this provider

    90 		IComponentProvider result = (IComponentProvider) providers.get(id);

    91 		if (result == null) {

    92 	        result = loadExtensions(id);

    93 	        providers.put(id, result);

    94 		}

    95 		return result;

    96 	}

    97 

    98     /**

    99      * Set the component provider

   100      * <p>

   101      * For testing to set a provider without requiring a running workbench.

   102      * @param id a string representing the provider

   103      * @param provider the provider instance (must not be null)

   104      */

   105     public synchronized void setProvider(String id, IComponentProvider provider) {

   106         Check.checkArg(id);

   107         Check.checkArg(provider);

   108         providers.put(id, provider);

   109     }

   110     

   111     private IComponentProvider loadExtensions(String id) throws CoreException {

   112         IComponentProvider result = null;

   113         

   114         // Get implementors of the componentProvider extension point

   115         IExtensionRegistry er = Platform.getExtensionRegistry();

   116         if (er == null)

   117             return null;

   118         

   119         IExtensionPoint ep = er.getExtensionPoint(

   120                 UIModelPlugin.PLUGIN_ID, PROVIDER_EXTENSION);

   121 

   122         IExtension matched = null;

   123         

   124         // Iterate over all providers looking for the requested one

   125         IExtension[] extensions = ep.getExtensions();

   126         for (int i = 0; i < extensions.length; i++) {

   127 			IExtension extension = extensions[i];

   128 			IConfigurationElement[] ces = extension.getConfigurationElements();

   129 			if (ces != null && ces.length >= 1) {

   130 				IConfigurationElement providerElement = ces[0];

   131 				String name = providerElement.getAttribute("name"); //$NON-NLS-1$

   132 				if (name != null && name.equals(id)) {

   133 					if (providerElement.getAttribute("class") != null) { //$NON-NLS-1$

   134                         if (result != null) {

   135                             Logging.log(UIModelPlugin.getDefault(), 

   136                                     Logging.newStatus(UIModelPlugin.getDefault(),

   137                                             IStatus.ERROR,

   138                                             MessageFormat.format(Messages.getString("ComponentSystem.1"),

   139                                                     new Object[] { id, extension.getUniqueIdentifier(), matched.getUniqueIdentifier() })

   140                                                     

   141                                             ));

   142                         } else {

   143                             result = (IComponentProvider) providerElement.createExecutableExtension("class"); //$NON-NLS-1$

   144                             matched = extension;

   145                         }

   146 					}

   147 				}

   148 			}

   149         }

   150         return result;

   151     }

   152 }