Question

I need to do a validation of an e-mail using annotation + regex. I tried to use the following:

@NotNull
@Pattern(regexp=".+@.+\\.[a-z]+")
private String email;

However, I don’t know how to print an error message when I have an incorrect e-mail address in the email field. Any ideas?

Answer 1

First you should add a message attribute to your Pattern annotation.
Assume that your mail variable is part of some class User:

class User{
@NotNull
@Pattern(regexp=".+@.+\\.[a-z]+", message="Invalid email address!")
private String email;
}

Then you should define a validator:

ValidatorFactory vf = Validation.buildDefaultValidatorFactory();
Validator validator = vf.getValidator();
User user = new User();
user.setEmail("[e-mail]");
Set<ConstraintViolation<User>> constraintViolations = validator
        .validate(user);

Then find validation errors.

for (ConstraintViolation<Object> cv : constraintViolations) {
      System.out.println(String.format(
          "Error here! property: [%s], value: [%s], message: [%s]",
          cv.getPropertyPath(), cv.getInvalidValue(), cv.getMessage()));
}