how to say this field has email annotation from outside-CodePudding

@NotNull(message = "emailAddress is mandatory")
@NotEmpty(message = "emailAddress cannot be empty")
@Email(message = "Invalid Email")
private String emailAddress;

I just want to know from outside , emailAdress has Email annotation. Is there any way that we can say it is an email annotaion?

CodePudding user response：

You can use reflection for this. The following test passes:

 public class MyTest {

    @Test
    public void test() throws NoSuchFieldException {
        HasEmailAddressValidator hasEmailAddressValidator = new HasEmailAddressValidator();
        boolean result = hasEmailAddressValidator.hasEmailAddress(MyClass.class);

        assertTrue(result);
    }

    @NoArgsConstructor
    static
    class HasEmailAddressValidator {
        public boolean hasEmailAddress(Class<?> clazz) throws NoSuchFieldException {
            return clazz.getDeclaredField("email").isAnnotationPresent(Email.class);
        }
    }

    @Data
    static
    class MyClass {
        @Email(message = "this is an email address")
        private String email;
    }
}

CodePudding user response：

Create your custome Annotation.

`import static java.lang.annotation.ElementType.ANNOTATION_TYPE;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.TYPE;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;

import javax.validation.Constraint;
import javax.validation.Payload;

@Target({ TYPE, FIELD, ANNOTATION_TYPE })
@Retention(RUNTIME)
@Constraint(validatedBy = EmailValidator.class)
@Documented
public @interface ValidEmail {

    String message() default "Invalid Email";

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

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

// Email Validator

import java.util.regex.Matcher;
import java.util.regex.Pattern;

import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;

public class EmailValidator implements ConstraintValidator<ValidEmail, String> {
    private static final String EMAIL_PATTERN = "^[_A-Za-z0-9-\\ ] (\\.[_A-Za-z0-9-] )*@"   "[A-Za-z0-9-] (\\.[A-Za-z0-9] )*(\\.[A-Za-z]{2,})$";
    private static final Pattern PATTERN = Pattern.compile(EMAIL_PATTERN);

    @Override
    public boolean isValid(final String username, final ConstraintValidatorContext context) {
        return (validateEmail(username));
    }

    private boolean validateEmail(final String email) {
        Matcher matcher = PATTERN.matcher(email);
        return matcher.matches();
    }
}

// Now in your DTO and Model

    @ValidEmail
    @NotNull
    @Size(min = 1, message = "Invalid Email")
    private String email;