Bean Validation Example

beanValidationExample

public class User {
	@NotNull
	@Email
	private String email;

	@ValidUsername
	private String username;

	@NotNull
	private String name;

	@NotNull(message = "password.null")
	@Size(min = 3, max = 255, message = "password.length")
	private String password;
}


@NotEmpty
@Length(min = 3, max = 100)
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
@Constraint(validatedBy = UsernameValidationConstraint.class)
@Documented
public @interface ValidUsername {
	String message() default "{m2.constraints.username.invalid.message}";

	Class<?>[] groups() default {};

	Class<? extends Payload>[] payload() default {};
}


public class UsernameValidationConstraint implements ConstraintValidator<ValidUsername, String> {

	@SuppressWarnings("unused")
	private String message;

	// any lowercase letter, number, and the following special chars: . @ _ -
	private static final String PATTERN_STRING = "^[a-zA-Z0-9\\.@_-]+$";

	private Pattern pattern = Pattern.compile(PATTERN_STRING);

	@Override
	public void initialize(ValidUsername constraintAnnotation) {
		message = constraintAnnotation.message();
	}

	@Override
	public boolean isValid(String value, ConstraintValidatorContext context) {
		boolean valid = false;

		if (value != null) {
			valid = pattern.matcher(value).matches();
		}
		return valid;
	}
}