org.eclipse.scout.sdk.ui/src/org/eclipse/scout/sdk/ui/internal/extensions/TechnologyExtensionPoint.java

/*******************************************************************************
 * Copyright (c) 2010 BSI Business Systems Integration AG.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     BSI Business Systems Integration AG - initial API and implementation
 ******************************************************************************/
package org.eclipse.scout.sdk.ui.internal.extensions;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;

import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.IExtension;
import org.eclipse.core.runtime.IExtensionPoint;
import org.eclipse.core.runtime.IExtensionRegistry;
import org.eclipse.core.runtime.Platform;
import org.eclipse.scout.commons.StringUtility;
import org.eclipse.scout.sdk.ui.extensions.technology.IScoutTechnologyHandler;
import org.eclipse.scout.sdk.ui.internal.ScoutSdkUi;
import org.eclipse.scout.sdk.ui.internal.extensions.technology.Technology;

public final class TechnologyExtensionPoint {

  public static final String EXTENSION_ID = "technology";
  public static final String TAG_TECH = "technology";
  public static final String TAG_HANDLER = "handler";
  public static final String ATTR_NAME = "name";
  public static final String ATTR_ID = "id";
  public static final String ATTR_TECH = "technology";
  public static final String ATTR_CLASS = "class";
  public static final String ATTR_CATEGORY = "category";

  private static volatile HashSet<Technology> technologies;
  private static final Object LOCK = new Object();

  private TechnologyExtensionPoint() {
  }

  private static Map<String /* tech id */, ArrayList<IScoutTechnologyHandler>> getHandlers() {
    HashMap<String, ArrayList<IScoutTechnologyHandler>> techHandlers = new HashMap<String, ArrayList<IScoutTechnologyHandler>>();
    IExtensionRegistry reg = Platform.getExtensionRegistry();
    IExtensionPoint xp = reg.getExtensionPoint(ScoutSdkUi.PLUGIN_ID, EXTENSION_ID);
    IExtension[] extensions = xp.getExtensions();
    for (IExtension extension : extensions) {
      IConfigurationElement[] elements = extension.getConfigurationElements();
      for (IConfigurationElement element : elements) {
        if (TAG_HANDLER.equals(element.getName())) {
          try {
            String techId = element.getAttribute(ATTR_TECH);
            ArrayList<IScoutTechnologyHandler> handlers = techHandlers.get(techId);
            if (handlers == null) {
              handlers = new ArrayList<IScoutTechnologyHandler>();
              techHandlers.put(techId, handlers);
            }
            IScoutTechnologyHandler handler = (IScoutTechnologyHandler) element.createExecutableExtension(ATTR_CLASS);
            handlers.add(handler);
          }
          catch (CoreException e) {
            ScoutSdkUi.logError("Unable to load technology handler class '" + element.getAttribute(ATTR_CLASS) + "'", e);
          }
        }
      }
    }
    return techHandlers;
  }

  public static Technology[] getTechnologyExtensions() {
    if (technologies == null) {
      synchronized (LOCK) {
        if (technologies == null) {
          Map<String, ArrayList<IScoutTechnologyHandler>> handlers = getHandlers();
          HashSet<Technology> techs = new HashSet<Technology>();
          IExtensionRegistry reg = Platform.getExtensionRegistry();
          IExtensionPoint xp = reg.getExtensionPoint(ScoutSdkUi.PLUGIN_ID, EXTENSION_ID);
          IExtension[] extensions = xp.getExtensions();
          for (IExtension extension : extensions) {
            IConfigurationElement[] elements = extension.getConfigurationElements();
            for (IConfigurationElement element : elements) {
              if (TAG_TECH.equals(element.getName())) {
                String id = element.getAttribute(ATTR_ID);
                String name = element.getAttribute(ATTR_NAME);
                String category = element.getAttribute(ATTR_CATEGORY);
                if (!StringUtility.hasText(category)) {
                  category = null;
                }
                if (StringUtility.hasText(name) && StringUtility.hasText(id)) {
                  Technology t = new Technology(id, name, category);
                  t.addAllHandlers(handlers.get(id));
                  techs.add(t);
                }
              }
            }
          }
          technologies = techs;
        }
      }
    }
    return technologies.toArray(new Technology[technologies.size()]);
  }
}