String perspective =
		"<extension " +
				"point=\"org.eclipse.ui.perspectives\">" +
			"<perspective " +
				"class=\"perspectivefactory.PerspectiveFactory2\" " +
				"icon=\"icons/error.gif\" " +
				"id=\"Perspective Creator.perspective2\" " +
				"name=\"name\">" +
			"</perspective>" +
		"</extension>";

try (InputStream in = new ByteArrayInputStream (perspective.getBytes (Charset.defaultCharset ()))){
	IContributor contributor = ContributorFactoryOSGi.createContributor (Platform.getBundle (Activator.PLUGIN_ID));
	Platform.getExtensionRegistry ().addContribution (in, contributor, false, null, null, null);
}catch (UnsupportedEncodingException e){
}catch (IOException e){
	Utils.log (e);
}

org.eclipse.e4.core.di.InjectionException: java.lang.IllegalArgumentException: Unauthorized access to the ExtensionRegistry.addContribution() method. Check if proper access token is supplied.

public static boolean addContribution (String contribution){
	boolean added = false;
	
	try (InputStream in =
			new ByteArrayInputStream (contribution.getBytes (Charset.defaultCharset ()));){
		IContributor contributor =
				ContributorFactoryOSGi.createContributor (Platform
						.getBundle (Activator.PLUGIN_ID));
		IExtensionRegistry registry = Platform.getExtensionRegistry ();
		
		/*
		 * To add a contribution we need a user or master token. These tokens cannot be
		 * obtained explicitly because the Equinox bundle creates and uses them internally
		 * to prevent the addition of heavy consuming memory stuff.
		 * See: https://bugs.eclipse.org/bugs/show_bug.cgi?id=295035
		 * 
		 * But there's still a way to obtain a master token. See below. The warning
		 * supression is because the unauthorized access to the ExtensionRegistry.
		 */
		@SuppressWarnings ("restriction")
		Field field =
				org.eclipse.core.internal.registry.ExtensionRegistry.class
						.getDeclaredField ("masterToken");
		field.setAccessible (true);
		Object masterToken = field.get (registry);
		
		added = registry.addContribution (in, contributor, false, null, null, masterToken);
	}catch (UnsupportedEncodingException e){
	}catch (NoSuchFieldException e){
		Log.error (e);
	}catch (SecurityException e){
		Log.error (e);
	}catch (IllegalArgumentException e){
		Log.error (e);
	}catch (IllegalAccessException e){
		Log.error (e);
	}catch (IOException e){
		Log.error (e);
	}
	
	return added;
}

boolean added = Registry.addContribution (
		"<extension " +
				"point=\"org.eclipse.ui.perspectives\">" +
			"<perspective " +
				"class=\"gll.perspective_creator.ui.EmptyPerspective\" " +
				"icon=\"images/error.gif\" " +
				"id=\"gll.perspective_creator.emptyPerspective\" " +
				"name=\"Empty Perspective\">" +
			"</perspective>" +
		"</extension>");