private String logError(Throwable t) {
		logger.error("Caught exception while handling a request", t);
		// TODO: use a more semantically correct VndError 'logref'
		return t.getClass().getSimpleName();
	}
Handles the case where client tried to deploy something that is has an invalid definition.
spring-xd-dirt/src/main/java/org/springframework/xd/dirt/rest/RestControllerAdvice.java