code: private synchronized void fetchMappingContextAndConversionService() {
  		if(mappingContext == null) {
  			MongoConverter mongoConverter = this.mongoTemplate.getConverter();
  			mappingContext = mongoConverter.getMappingContext();
  			conversionService = mongoConverter.getConversionService();
  
  			MongoPersistentEntity<?> persistentEntity = mappingContext.getPersistentEntity(entityClass);
  			MongoPersistentProperty idProperty = persistentEntity.getIdProperty();
  			this.idKey = idProperty == null ? "_id" : idProperty.getName();
  		}
  	}
docs: Get the basic services from mongo template