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Home » Eclipse Projects » Eclipse Platform » How to reduce hard-coding IDs(Ever wondered how to reduce hard coding IDs in your classes?)
How to reduce hard-coding IDs [message #514337] Sun, 14 February 2010 11:55 Go to next message
Eugene  is currently offline Eugene
Messages: 25
Registered: July 2009
Junior Member
I've always been frustrated by having to include various IDs in my eclipse implemenation classes. For example, If I use the wizards extension to contribute a new wizard, that wizard gets and ID, which may or may not be needed at some point.

I've found that when I change the ID in the plugin.xml for any reason, that any other place the ID is listed will get out of sync, and there is no refactoring support for this since the IDs are lightweight strings.

I've come up with this approach to extract the IDs from the extension registry, I would like your feedback (positive or negative) on this method:

	  /**
	   * Configuration elements in the typical plugin.xml file can specify class,
	   * id, and other similar attributes. This method can be used to determine the
	   * unique ID assigned to a class in the plugin.xml file. However, if the same
	   * class is assigned multiple unique IDs, then this method will fail and throw
	   * a RuntimeException.
	   * <br><br>
	   * Example use: String id = getUniqueID(getClass(), "defaultHandler");
	   * <br><br>
	   * Lazy loading features are preserved when using this method.
	   * 
	   * @param clazz the class for which a unique ID should be retrieved.
	   * @param specification the name of the attribute whose value is the class
	   * @return the unique ID for the class, or null if one is not specified
	   * @throws RuntimeException if more than one valid ID is found.
	   */	
	  public static String getUniqueID(Class<?> clazz, String specification) {
		  String id = classToIdMap.get(clazz);
		  if(id == null) {
			  try {			
				  IExtensionRegistry extensionRegistry = Platform.getExtensionRegistry();
				  IExtensionPoint[] extensionPoints = extensionRegistry.getExtensionPoints();
				  for(IExtensionPoint extensionPoint : extensionPoints) {
					  IConfigurationElement[] configurationElements
					  = extensionRegistry.getConfigurationElementsFor(extensionPoint.
							  getUniqueIdentifier());
	
					  int idCount = 0;
					  for(IConfigurationElement configurationElement : configurationElements) {
						  String attribute = configurationElement.getAttribute(specification);
	
						  String namespaceIdentifier = configurationElement.getNamespaceIdentifier();
						  if(attribute != null
								  && !namespaceIdentifier.equals("org.eclipse.emf.ecore.editor") // ignore this namespace, it causes problems
								  && attribute.equals(clazz.getName())) {
							  Object object = configurationElement.createExecutableExtension(specification);
							  if(object != null) {
								  Class<?> class1 = object.getClass();
								  Class<?> class2 = clazz;
								  if(class1.equals(class2)) {
									  if(idCount == 0) {
										  id = configurationElement.getAttribute("id");
										  idCount++;
									  }
	
									  else {
										  throw new RuntimeException("Multiple IDs" +
												  " found for " + specification + " " + clazz.getName());
									  }
								  }
							  }
						  }
					  }
				  }
			  }
	
			  catch (Exception ex) {
				  LogUtil.error(ex);
			  }
		  }

		  return id;
	  }
Re: How to reduce hard-coding IDs [message #514376 is a reply to message #514337] Mon, 15 February 2010 01:29 Go to previous message
Prakash G.R. is currently offline Prakash G.R.
Messages: 621
Registered: July 2009
Senior Member
On 14/02/10 10:25 PM, Eugene wrote:
> I've always been frustrated by having to include various IDs in my
> eclipse implemenation classes. For example, If I use the wizards
> extension to contribute a new wizard, that wizard gets and ID, which may
> or may not be needed at some point.
>
> I've found that when I change the ID in the plugin.xml for any reason,
> that any other place the ID is listed will get out of sync, and there is
> no refactoring support for this since the IDs are lightweight strings.
>
> I've come up with this approach to extract the IDs from the extension
> registry, I would like your feedback (positive or negative) on this method:
>
> /**
> * Configuration elements in the typical plugin.xml file can specify class,
> * id, and other similar attributes. This method can be used to determine
> the
> * unique ID assigned to a class in the plugin.xml file. However, if the
> same
> * class is assigned multiple unique IDs, then this method will fail and
> throw
> * a RuntimeException.
> * <br><br>
> * Example use: String id = getUniqueID(getClass(), "defaultHandler");
> * <br><br>
> * Lazy loading features are preserved when using this method.
> * * @param clazz the class for which a unique ID should be retrieved.
> * @param specification the name of the attribute whose value is the class
> * @return the unique ID for the class, or null if one is not specified
> * @throws RuntimeException if more than one valid ID is found.
> */
> public static String getUniqueID(Class<?> clazz, String specification) {
> String id = classToIdMap.get(clazz);
> if(id == null) {
> try {
> IExtensionRegistry extensionRegistry = Platform.getExtensionRegistry();
> IExtensionPoint[] extensionPoints = extensionRegistry.getExtensionPoints();
> for(IExtensionPoint extensionPoint : extensionPoints) {
> IConfigurationElement[] configurationElements
> = extensionRegistry.getConfigurationElementsFor(extensionPoint .
> getUniqueIdentifier());
>
> int idCount = 0;
> for(IConfigurationElement configurationElement : configurationElements) {
> String attribute = configurationElement.getAttribute(specification);
>
> String namespaceIdentifier = configurationElement.getNamespaceIdentifier();
> if(attribute != null
> && !namespaceIdentifier.equals("org.eclipse.emf.ecore.editor") // ignore
> this namespace, it causes problems
> && attribute.equals(clazz.getName())) {
> Object object =
> configurationElement.createExecutableExtension(specification );
> if(object != null) {
> Class<?> class1 = object.getClass();
> Class<?> class2 = clazz;
> if(class1.equals(class2)) {
> if(idCount == 0) {
> id = configurationElement.getAttribute("id");
> idCount++;
> }
>
> else {
> throw new RuntimeException("Multiple IDs" +
> " found for " + specification + " " + clazz.getName());
> }
> }
> }
> }
> }
> }
> }
>
> catch (Exception ex) {
> LogUtil.error(ex);
> }
> }
>
> return id;
> }


It would be great if PDE can automagically search and update the
java/text files when the id field in an extension changes. If it doable,
you can file an enhancement request in Bugzilla. cc-ing pde newsgroup
for comments.

- Prakash
Platform UI Team, IBM

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