How to use

IExtensionRegistry

in

org.eclipse.core.runtime

private void readExtentions() {
  IExtensionRegistry registry = Platform.getExtensionRegistry();
  IExtensionPoint point = registry.getExtensionPoint(PDECore.PLUGIN_ID, TARGET_LOC_EXTPT);
  if (point == null)
    return;
  IExtension[] extensions = point.getExtensions();
  for (int i = 0; i < extensions.length; i++) {
    IConfigurationElement[] elements = extensions[i].getConfigurationElements();
    for (int j = 0; j < elements.length; j++) {
      String type = elements[j].getAttribute(ATTR_TYPE);
      if (type != null) {
        fExtentionMap.put(type, elements[j]);
      }
    }
  }
}

public SearchPageRegistry() {
  fExtensionToInstance= new HashMap<>();
  fResultClassNameToExtension= new HashMap<>();
  fExtensions= Platform.getExtensionRegistry().getConfigurationElementsFor(ID_EXTENSION_POINT);
  for (IConfigurationElement fExtension : fExtensions) {
    fResultClassNameToExtension.put(fExtension.getAttribute(ATTRIB_SEARCH_RESULT_CLASS), fExtension);
  }
}

/**
 * Connects this manager to the platform's extension registry.
 */
public void connect() {
  Platform.getExtensionRegistry().addRegistryChangeListener(this, RefactoringCore.ID_PLUGIN);
}

private void readRegistryImpl() {
  extensionRegistry.addRegistryChangeListener(this, namespace);
  
  IExtension[] extensions = extensionRegistry.getExtensionPoint(
      namespace, PT_ENVIRONMENTS).getExtensions();
  
  for (IExtension extension : extensions) {
    read(extension);
  }
}

private void loadElements() {
  fTargets = new HashMap();
  IExtensionRegistry registry = Platform.getExtensionRegistry();
  registry.addRegistryChangeListener(this);
  IConfigurationElement[] elements = registry.getConfigurationElementsFor("org.eclipse.pde.core.targets"); //$NON-NLS-1$
  add(elements);
}

/**
 * Loads runtime classpath extensions
 */
private void initializeRuntimeClasspathExtensions() {
  IExtensionPoint extensionPoint= Platform.getExtensionRegistry().getExtensionPoint(LaunchingPlugin.ID_PLUGIN, ID_EXTENSION_POINT_RUNTIME_CLASSPATH_ENTRIES);
  IConfigurationElement[] configs= extensionPoint.getConfigurationElements();
  fClasspathEntryExtensions = new HashMap<String, IConfigurationElement>(configs.length);
  for (int i= 0; i < configs.length; i++) {
    fClasspathEntryExtensions.put(configs[i].getAttribute("id"), configs[i]); //$NON-NLS-1$
  }
}

IConfigurationElement[] config = Platform.getExtensionRegistry()
    .getConfigurationElementsFor(
        Activator.EXTENSION_POINT_ID_MAPPER);
try {
  for (IConfigurationElement e : config) {
    final Object o = e.createExecutableExtension("class");
    if (o instanceof ThemePreferenceMapper) {
      String pluginId = e.getAttribute("pluginId");
      ThemePreferenceMapper mapper = (ThemePreferenceMapper) o;
      mapper.setPluginId(pluginId);
      if (o instanceof GenericMapper) {
        String xml = e.getAttribute("xml");
        String contributorPluginId = e.getContributor()
            .getName();
        Bundle bundle = Platform.getBundle(contributorPluginId);
        InputStream input = (InputStream) bundle.getResource(
            xml).getContent();

private static String[] readGlobalLoadingPluginNames() {
  IExtensionRegistry reg = Platform.getExtensionRegistry();
  IExtensionPoint exPoint = reg.getExtensionPoint(ID, "globalPluginResourceLoad"); //$NON-NLS-1$
  IExtension[] extensions = exPoint.getExtensions();
  String[] names = new String[extensions.length];
  if (extensions.length > 0) {
    for (int i = 0; i < extensions.length; i++)
      names[i] = extensions[i].getContributor().getName();
  }
  return names;
}

private Map<String, String> createThemeAssociations() {
  Map<String, String> result = new HashMap<>();
  IExtensionRegistry registry = RegistryFactory.getRegistry();
  IExtensionPoint extPoint = registry.getExtensionPoint(E4_THEME_EXTENSION_POINT);
  for (IExtension e : extPoint.getExtensions()) {
    for (IConfigurationElement ce : e.getConfigurationElements()) {
      if (ce.getName().equals(ATT_THEME_ASSOCIATION)) {
        String themeId = ce.getAttribute(ATT_THEME_ID);
        String osVersion = ce.getAttribute(ATT_OS_VERSION);
        result.put(osVersion != null ? themeId + osVersion : themeId,
            ce.getAttribute(ATT_COLOR_AND_FONT_ID));
      }
    }
  }
  return result;
}

private synchronized void ensureCleanUpInitializersRegistered() {
  if (fCleanUpInitializerDescriptors != null)
    return;
  ArrayList<CleanUpInitializerDescriptor> result= new ArrayList<>();
  IExtensionPoint point= Platform.getExtensionRegistry().getExtensionPoint(JavaPlugin.getPluginId(), EXTENSION_POINT_NAME);
  IConfigurationElement[] elements= point.getConfigurationElements();
  for (int i= 0; i < elements.length; i++) {
    IConfigurationElement element= elements[i];
    if (CLEAN_UP_INITIALIZER_CONFIGURATION_ELEMENT_NAME.equals(element.getName())) {
      result.add(new CleanUpInitializerDescriptor(element));
    }
  }
  fCleanUpInitializerDescriptors= result.toArray(new CleanUpInitializerDescriptor[result.size()]);
}

private void setupWizardPluginIDMap() {
  wizardPluginIDMap = new HashMap();
  // get editor plugin and save it to a hash map
  // Note: editors extension id is different from editor id
  IExtensionPoint[] point = new IExtensionPoint[]{Platform.getExtensionRegistry().getExtensionPoint(ORG_ECLIPSE_UI, "exportWizards"), //$NON-NLS-1$
        Platform.getExtensionRegistry().getExtensionPoint(ORG_ECLIPSE_UI, "importWizards"), //$NON-NLS-1$
        Platform.getExtensionRegistry().getExtensionPoint(ORG_ECLIPSE_UI, "newWizards"), //$NON-NLS-1$
        Platform.getExtensionRegistry().getExtensionPoint("org.eclipse.wst.common.frameworks.ui", "extendableWizard")}; //$NON-NLS-1$ //$NON-NLS-2$
  for (int x = 0; x < point.length; x++) {
    IConfigurationElement[] elements = point[x].getConfigurationElements();
    for (int i = 0; i < elements.length; i++) {
      String wizardID = elements[i].getAttribute("id"); //$NON-NLS-1$
      String pluginID = elements[i].getDeclaringExtension().getNamespace();
      wizardPluginIDMap.put(wizardID, pluginID);
    }
  }
}

/**
 * Load extensions
 */
private void initialize() {
  fConfigurations = new HashMap<>();
  IExtensionPoint point= Platform.getExtensionRegistry().getExtensionPoint(DebugUIPlugin.getUniqueIdentifier(), EXTENSION_POINT_STRING_VARIABLE_PRESENTATIONS);
  IConfigurationElement elements[]= point.getConfigurationElements();
  for (int i = 0; i < elements.length; i++) {
    IConfigurationElement element = elements[i];
    String name= element.getAttribute(ATTR_NAME);
    if (name == null) {
      DebugUIPlugin.logErrorMessage(MessageFormat.format("String variable presentation extension missing required 'variableName' attribute: {0}", new Object[] { element.getDeclaringExtension().getLabel() })); //$NON-NLS-1$
      continue;
    }
    fConfigurations.put(name, element);
  }
}

  public void stop ()
  {
    Platform.getExtensionRegistry ().removeRegistryChangeListener ( this.changeListener );
  }
}

protected IConfigurationElement[] getExtendedConfigurationElements() {
  IExtensionRegistry registry = Platform.getExtensionRegistry();
  IExtensionPoint exampleWizardXP = registry.getExtensionPoint(EXAMPLE_WIZARD_XP_ID);
  if (exampleWizardXP == null) {
    return new IConfigurationElement[0];
  }
  IExtension extension = exampleWizardXP.getExtension(getWizardExtensionId());
  if (extension != null) {
    return extension.getConfigurationElements();
  }
  IConfigurationElement[] exampleWizardCEs = exampleWizardXP.getConfigurationElements();
  return exampleWizardCEs;
}

/**
 * Loads adapters registered with the adapters extension point from
 * the plug-in registry.  Note that the actual factory implementations
 * are loaded lazily as they are needed.
 */
public boolean addFactories(AdapterManager adapterManager) {
  IExtensionPoint point = RegistryFactory.getRegistry().getExtensionPoint(ADAPTER_POINT_ID);
  if (point == null)
    return false;
  boolean factoriesAdded = false;
  IExtension[] extensions = point.getExtensions();
  for (int i = 0; i < extensions.length; i++) {
    IConfigurationElement[] elements = extensions[i].getConfigurationElements();
    for (int j = 0; j < elements.length; j++) {
      AdapterFactoryProxy proxy = AdapterFactoryProxy.createProxy(elements[j]);
      if (proxy != null) {
        adapterManager.registerFactory(proxy, proxy.getAdaptableType());
        factoriesAdded = true;
      }
    }
  }
  RegistryFactory.getRegistry().addListener(this, ADAPTER_POINT_ID);
  return factoriesAdded;
}

private static IExtension[] getPerspectiveExtensions() {
  IExtensionPoint point = Platform.getExtensionRegistry().getExtensionPoint(PlatformUI.PLUGIN_ID,
      IWorkbenchRegistryConstants.PL_PERSPECTIVE_EXTENSIONS);
  if (point == null) {
    return null;
  }
  IExtension[] extensions = point.getExtensions();
  extensions = RegistryReader.orderExtensions(extensions);
  return extensions;
}

private IConfigurationElement[] loadElements() {
  IExtensionPoint point = Platform.getExtensionRegistry()
      .getExtensionPoint("org.eclipse.ui", "installationPages"); //$NON-NLS-1$ //$NON-NLS-2$
  return point.getConfigurationElements();
}

private static synchronized Set<DelegateCommandHandlerDescriptor> getDelegateCommandHandlerDescriptors() {
  if (fgContributedCommandHandlers == null) {
    IConfigurationElement[] elements = Platform.getExtensionRegistry().getConfigurationElementsFor(EXTENSION_POINT_ID);
    fgContributedCommandHandlers = Stream.of(elements).map(e -> new DelegateCommandHandlerDescriptor(e)).collect(Collectors.toSet());
  }
  return fgContributedCommandHandlers;
}

public ForwardingDanglingReferenceResolver ()
{
  Platform.getExtensionRegistry ().addListener ( this, EXPT_DANGLING_RESOLVER );
  buildCache ();
}

public Bundle getExtensionPointBundle(IExtension extension) {
  IExtensionRegistry  registry = getExtensionRegistry();
  String extensionPtId = extension.getExtensionPointUniqueIdentifier();
  IExtensionPoint extensionPt = registry.getExtensionPoint(extensionPtId);
  IContributor contributor = extensionPt.getContributor();
  return getBundle(contributor);
}