public Message<?> process(Message<?> message, String timeField) throws ParseException {
		if (message == null) {
			return null;
		}

		Double increment = incrementExpression.getValue(evaluationContext, message, Double.class);
		String counterName = computeMetricName(message);

		if (timeField == null) {
			this.aggregateCounterRepository.increment(counterName, increment.longValue());
		}
		else {
			this.aggregateCounterRepository.increment(counterName, increment.longValue(),
					dateFormat.parseDateTime(timeField));
		}
		return message;
	}
Handles incoming messages for the {@code aggregate-counter} module, resolves SpEL expressions
as needed and delegate the heavy lifting to an {@link AggregateCounterRepository}.

@author Luke Taylor
@author Eric Bottard
spring-xd-analytics/src/main/java/org/springframework/xd/analytics/metrics/integration/AggregateCounterHandler.java