java Annotation Demo

import java.lang.annotation.Annotation;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.lang.reflect.Field;
import java.util.regex.Pattern;

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@interface EmailAddress {

}

class student {
    String sname;
    int sid;
    @EmailAddress
    String email;

    public student(int _sid, String _sname, String _email) {
        sid = _sid;
        sname = _sname;
        email = _email;
    }

    public String toString() {
        return "id:" + sid + "sname:" + sname + " email:" + email;
    }
}

class emailValidator {
    static boolean isvalidemail(String email) {
        Pattern ptn = Pattern
                .compile("^[a-z0-9!#$%&‘*+/=?^_`{|}~-]+(?:\\.[a-z0-9!#$%&‘*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?$");
        return ptn.matcher(email).matches();
    }

    public static void checkEmailType(Object obj,
            Class<? extends Annotation> antcls)
            throws IllegalArgumentException, IllegalAccessException {
        Class<?> cls = obj.getClass();
        for (Field field : cls.getDeclaredFields()) {
            if (field.isAnnotationPresent(antcls)) {
                if (antcls.isAssignableFrom(EmailAddress.class)) {
                    if (!isvalidemail(field.get(obj).toString())) {
                        try {
                            System.out.println("Anotation " + antcls.getName()
                                    + " validate is not pass for value:"
                                    + "class " + obj.getClass().getName()
                                    + " field " + field.getName() + ":"
                                    + field.get(obj).toString());
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                    }
                }
            }
        }

    }
}

public class testAnnotation {

    public static void main(String[] args) throws IllegalArgumentException,
            IllegalAccessException {
        student s = new student(1, "yaoshuya", "yaoshuya@ss.dd.dfd..com");
        System.out.println(student.class.isAssignableFrom(s.getClass()));
        emailValidator.checkEmailType(s, EmailAddress.class);
        // System.out.println(emailValidator.isvalidemail(s.email));
    }
}