@Override
		public boolean isValid(CharSequence value, ConstraintValidatorContext context) {
			if (value == null) {
				return true;
			}
			try {
				new SimpleDateFormat(value.toString());
			}
			catch (IllegalArgumentException e) {
				if (DEFAULT_MESSAGE.equals(this.message)) {
					context.disableDefaultConstraintViolation();
					context.buildConstraintViolationWithTemplate(e.getMessage()).addConstraintViolation();
				}
				return false;
			}
			return true;
		}
Defines several {@link DateFormat} annotations on the same element.

@see DateFormat
spring-xd-module-spi/src/main/java/org/springframework/xd/module/options/validation/DateFormat.java