IllegalArgumentException: Can´t serialize class (e

问题:

I successfully set up a MongoDB Database and my Java program is connecting to it fine. However, when I try to save an instance of this class, I get an error:

@Data
public class NormalUser extends User implements Serializable {

    private static final long serialVersionUID = 1324235L;

    public NormalUser(final String name, final String surname, final String address,
                      final String dni, final Gender gender, final String bankAccount) {
        super(name, surname, address, dni, gender, bankAccount, Role.NORMAL_USER, false);
    }
}

(Please note I am using Lombok @Data annotation and that the class extends another class that uses the same annotation and only has the constructor and the attributes.)

The error I am getting is weird from my point of view, as long as it says the class can´t be serialized even it implements Serializable:

Exception in thread "main" java.lang.IllegalArgumentException: can't serialize class entities.users.NormalUser
    at org.bson.BasicBSONEncoder._putObjectField(BasicBSONEncoder.java:270)
    at org.bson.BasicBSONEncoder.putObject(BasicBSONEncoder.java:174)
    at org.bson.BasicBSONEncoder.putObject(BasicBSONEncoder.java:120)
    at com.mongodb.DefaultDBEncoder.writeObject(DefaultDBEncoder.java:27)
    at com.mongodb.OutMessage.putObject(OutMessage.java:289)
    at com.mongodb.DBApiLayer$MyCollection.insert(DBApiLayer.java:261)
    at com.mongodb.DBApiLayer$MyCollection.insert(DBApiLayer.java:226)
    at com.mongodb.DBCollection.insert(DBCollection.java:75)
    at com.mongodb.DBCollection.insert(DBCollection.java:59)
    at com.mongodb.DBCollection.insert(DBCollection.java:104)
    at repositories.UsersRepository.createUser(UsersRepository.java:35)
    at repositories.UsersRepository.main(UsersRepository.java:68)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)

UPDATE

Here is the super class:

@Data
public abstract class User implements Serializable {

    static final long serialVersionUID = 12314362564783L;

    private String surname;
    private String address;
    private String dni;
    private Gender gender;
    private String bankAccount;
    private Role role;
    private boolean admin;
    private String name;

    public User(final String name, final String surname, final String address,
                final String dni, final Gender gender, final String bankAccount,
                final Role role, final boolean admin) {
        this.name = name;
        this.surname = surname;
        this.address = address;
        this.dni = dni;
        this.gender = gender;
        this.bankAccount = bankAccount;
        this.role = role;
        this.admin = admin;
    }
}

UPDATE #2 Is this enough to serialize the enum Gender?

public enum Gender implements Serializable {

    MALE, FEMALE;
}