code: private final StringBuilder genericFlow(boolean newInstance){
  		
  		// if newInstance is true or mapping type of newField is ONLY_NULL_FIELDS
  		// write the mapping for the new field
  		if(newInstance || getMtd() == ONLY_NULL_FIELDS) 	
  			return sourceControl(fieldToCreate()); 
  		
  		// if is enrichment case and mapping type of destination is ALL_FIELDS
  		if(getMtd() == ALL_FIELDS && !destinationType().isPrimitive())
  			return  write(	  "   if(",getDestination(),"!=null){",newLine
  							  	   ,sourceControl(existingField()),
  							  "   }else{"						  ,newLine
  							  	   ,sourceControl(fieldToCreate()),
  							  "   }"						  	  ,newLine);
  		
  		// other cases
  		return sourceControl(existingField()); 
  	}
docs: This method specifies the general flow of the complex mapping.
  
  @param newInstance true if you need to create a new instance, false otherwise
  @return a StringBuilder containing the mapping