TriggerFactory.cls

/**
* Class TriggerFactory
*
* Used to instantiate and execute Trigger Handlers associated with sObjects.
*/
public with sharing class TriggerFactory
{
	// Generate unique executionId for debuging execution results
	private static String executionId;

	// Map to make sure each trigger handler only runs once
	private static Map<sObjectType, Boolean> recursions = new Map<sObjectType, Boolean>();

	/**
	* Public static method to create and execute a trigger handler
	*
	* Arguments:
	*  - Schema.sObjectType soType - Object type to process (SObject.sObjectType)
	*
	* Throws a TriggerException if a handler has not been created.
	*/
	public static void createHandler(Schema.sObjectType soType)
	{
		// Get a handler appropriate to the object being processed
		ITrigger handler = getHandler(soType);

		// Execute the handler for the trigger
		executionId = generateGUID();

		if(isFirstRun(soTYpe)) {
			System.DEBUG('[TF | ' + soType + '] - ' + executionId + ': Executing... ');
			execute(handler, soType);
		} else {
			System.DEBUG('[TF | ' + soType + '] - ' + executionId + ': Not Excuting (Recursive call)... ');
		}

		System.DEBUG('[TF | ' + soType + '] - ' + executionId + ': Ending... ');
	}

	/**
	* private static method to control the execution of the handler
	*
	* Arguments:
	*  - ITrigger handler - A Trigger Handler to execute
	*  - Schema.sObjectType soType - Object type to process (SObject.sObjectType)
	*/
	private static void execute(ITrigger handler, Schema.sObjectType soType)
	{
		// Before Trigger
		if (Trigger.isBefore)
		{
			// Call the bulk before to handle any caching of data and enable bulkification
			System.DEBUG('[TF | ' + soType + '] - ' + executionId + ': Executing Bulk Before. SOQL Count - ' + Limits.getQueries());

			handler.bulkBefore();

			System.DEBUG('[TF | ' + soType + '] - ' + executionId + ': Ending Bulk Before. SOQL Count - ' + Limits.getQueries());

			// Iterate through the records to be deleted passing them to the handler.
			if (Trigger.isDelete)
			{
				System.DEBUG('[TF | ' + soType + '] - ' + executionId + ': Executing Before Delete. SOQL Count - ' + Limits.getQueries());

				for (SObject so : Trigger.old)
				{
					handler.beforeDelete(so);
				}

				System.DEBUG('[TF | ' + soType + '] - ' + executionId + ': Ending Before Delete. SOQL Count - ' + Limits.getQueries());
			}
			// Iterate through the records to be inserted passing them to the handler.
			else if (Trigger.isInsert)
			{
				System.DEBUG('[TF | ' + soType + '] - ' + executionId + ': Executing Before Insert. SOQL Count - ' + Limits.getQueries());

				for (SObject so : Trigger.new)
				{
					handler.beforeInsert(so);
				}

				System.DEBUG('[TF | ' + soType + '] - ' + executionId + ': Ending Before Insert. SOQL Count - ' + Limits.getQueries());
			}
			// Iterate through the records to be updated passing them to the handler.
			else if (Trigger.isUpdate)
			{
				System.DEBUG('[TF | ' + soType + '] - ' + executionId + ': Executing Before Update. SOQL Count - ' + Limits.getQueries());

				for (SObject so : Trigger.old)
				{
					handler.beforeUpdate(so, Trigger.newMap.get(so.Id));
				}

				System.DEBUG('[TF | ' + soType + '] - ' + executionId + ': Ending Before Update. SOQL Count - ' + Limits.getQueries());
			}
		}
		else
		{
			// Call the bulk after to handle any caching of data and enable bulkification
			System.DEBUG('[TF | ' + soType + '] - ' + executionId + ': Executing Bulk After. SOQL Count - ' + Limits.getQueries());

			handler.bulkAfter();

			System.DEBUG('[TF | ' + soType + '] - ' + executionId + ': Executing Bulk After. SOQL Count - ' + Limits.getQueries());

			// Iterate through the records deleted passing them to the handler.
			if (Trigger.isDelete)
			{
				System.DEBUG('[TF | ' + soType + '] - ' + executionId + ': Executing After Delete. SOQL Count - ' + Limits.getQueries());

				for (SObject so : Trigger.old)
				{
					handler.afterDelete(so);
				}

				System.DEBUG('[TF | ' + soType + '] - ' + executionId + ': Ending After Delete. SOQL Count - ' + Limits.getQueries());
			}
			// Iterate through the records inserted passing them to the handler.
			else if (Trigger.isInsert)
			{
				System.DEBUG('[TF | ' + soType + '] - ' + executionId + ': Executing After Insert. SOQL Count - ' + Limits.getQueries());

				for (SObject so : Trigger.new)
				{
					handler.afterInsert(so);
				}

				System.DEBUG('[TF | ' + soType + '] - ' + executionId + ': Ending After Delete. SOQL Count - ' + Limits.getQueries());
			}
			// Iterate through the records updated passing them to the handler.
			else if (Trigger.isUpdate)
			{
				System.DEBUG('[TF | ' + soType + '] - ' + executionId + ': Executing After Update. SOQL Count - ' + Limits.getQueries());

				for (SObject so : Trigger.old)
				{
					handler.afterUpdate(so, Trigger.newMap.get(so.Id));
				}

				System.DEBUG('[TF | ' + soType + '] - ' + executionId + ': Ending After Delete. SOQL Count - ' + Limits.getQueries());
			}
		}

		System.DEBUG('[TF | ' + soType + '] - ' + executionId + ': Executing Final Function. SOQL Count - ' + Limits.getQueries());

		// Perform any post processing
		handler.andFinally();

		System.DEBUG('[TF | ' + soType + '] - ' + executionId + ': Ending Final Function. Overal SOQL Count - ' + Limits.getQueries());
		System.DEBUG('[TF | ' + soType + '] - ' + executionId + ': Ending Final Function. Overal SOQL MAX LIMIT - ' + Limits.getLimitQueries());
		System.DEBUG('[TF | ' + soType + '] - ' + executionId + ': Ending Final Function. Overal DML Count - ' + Limits.getDMLRows());
		System.DEBUG('[TF | ' + soType + '] - ' + executionId + ': Ending Final Function. Overal DML MAX LIMIT - ' + Limits.getLimitDMLRows());
	}

	/**
	* private static method to get the appropriate handler for the object type.
	*
	* Arguments:
	*  - Schema.sObjectType soType - Object type to locate (SObject.sObjectType)
	*
	* Returns: ITrigger - A trigger handler if one exists or null.
	*/
	private static ITrigger getHandler(Schema.sObjectType soType)
	{
		try {
			return (ITrigger)Type.forName(soType.getDescribe().getName() + 'TriggerHandler').newInstance();
		} catch(Exception e) {
			throw new TriggerException('No Trigger Handler registered for Object Type: ' + soType);
		}
	}

	/**
	* private static method to generate a unique GUID for grouping DEBUG Logs.
	*
	* Arguments: NA
	*
	* Returns: String in a GUID format
	*/
	private static String generateGUID()
	{
		Blob b = Crypto.GenerateAESKey(128);
		String h = EncodingUtil.ConvertTohex(b);
		return h.SubString(0,8)+ '-' + h.SubString(8,12) + '-' + h.SubString(12,16) + '-' + h.SubString(16,20) + '-' + h.substring(20);
	}

	/**
	* private static method to make sure the each trigger handler only runs once
	*
	* Arguments:
	*  - Schema.sObjectType soType - Object type to locate (SObject.sObjectType)
	*
	* Returns: True or False identify if the trigger handler has already ran
	*/
	private static Boolean isFirstRun(Schema.sObjectType soType) {
		if(!recursions.containsKey(soType)) {
			recursions.put(soType, true);
			return true;
		}

    return false;
  }
}