Validate only if the field is not Null

问题

I use JSR303 Spring Validation and I have the following;

@Digits(fraction = 0, integer = 15)
private String tpMobile;

Validation says Must be number between 10-15 digits, but the thing is this field is optional. So when user left it empty also the same error message shows.

So what I want to do is validate only if the field is not empty. If the field is empty skip validating that field

回答1:

Instead of using @Digit, I would like to suggest you to use @Pattern(message="YOUR_MESSAGE", regexp="REGULAR_EXPRESSION")

Main reason is that we show message for such set of values for which we want to restrict the user, here in your condition message is displayed for that value which you don't want to restrict.

So You wants to restrict user to enter anything other than blank space and numbers.Make a regular expression for that and use @Pattern with that.

For your case :

@Pattern(message="YOUR_MESSAGE", regexp="^(\\s*|\\d{10,15})$")

回答2:

Obviously, you form submits empty strings instead of nulls. Just check the value of tpMobile

来源：https://stackoverflow.com/questions/19262979/validate-only-if-the-field-is-not-null