@Pattern validation on a blank field

Question

I am using validation annotations to validate the Email field, Here the email field is not mandatory, Still when I click on submit, It is validating and throwing error message when the field is empty,

Here are the annotations:

@Pattern(regexp = "^[_A-Za-z0-9-\\+]+(\\.[_A-Za-z0-9-]+)*@[A-Za-z0-9-]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$", 
            message = "registration.label.useremailformat.invalidformat")
@Size(min = 6, max = 20, message = "registration.label.useremail.length")
@SafeHtml
private String userEmailId;

How can I skip @Pattern validation when the email field is empty and validate only when the value is given? Any help would be highly appreciated.

Answer 1

Modify your regexp to allow empty string and remove @Size:

@Pattern("^$|(<<old regexp>>)")
@SafeHtml
private String userEmailId;

... where <<old regex>> is a placeholder for your current lengthy regexp.