Portal User Interface

PortalUserService.java

// not real code...but you get the idea

public interface PortalUserService {
    public PortalUser get(int id);
    public PortalUser updatePassword(PortalUser paUser, String paNewPassword);
}

public class PortalUser {
    String username;
    String password;
}

KKMSUserImpl.java

// Notice we are IMPLEMENTING a PortalUser here.  Which requires us implement the "get" and "updatePassword" methods.
// PortalUserService  could care less on HOW we change the password.  Just so as long as we provide a method to do so
// Also, this makes KKMSUser == PortalUser.  They can be used interchangeably
// And since KKMS users are NOT stored in the same database as the Portal's users, 
// the Portal can still work with KKMS users because of this interface.  This "Impl" is telling Portal HOW to handle KKMS users.
// Plus, since the Portal would probably have multiple database connections, the "kkmsService" below would point the SQL Server DB.
// Once again, Portal could care less.  But the Portal would be able to use KKMS users as if they were all in the same database.  :-)

public class KKMSUserImpl implements PortalUserService {

    String username;
    String password;  // this must be 10 characters

    public KKMSUser get(int id) {
        return kkmsService.getUserById(id);  // kkmsService would have been Autowired
    }

    public KKMSUser updatePassword(KKMSUser paUser, String paNewPassword) {
        // remember, the portal has no idea WHERE or HOW this KKMS user is handled.  We are TELLING it here.

        // also, let's pretend that KKMS requires 10 characters for password.  Portal doesn't know about this.  Doesn't care.
        // but if you try to update a user that is of type KKMS, and the password < 10 characters, portal automatically knows there's a problem
        if(paNewPassword.length < 10) {
            throw new PasswordLengthInvalidException();
        }

        kkmsService.updatePassword(paNewPassword);
        return paUser;
    }
}

YMSUserImpl.java

// Here, we are implementing a YMS version of a Portal User.  
// Let's pretend that YMS is super strict and requires 12 characters in password and it must start with the letter 'A'

public class YMSUserImpl implements PortalUserService {
    String username;
    String password;   // must be 12 characters and start with the letter 'A'

    public YMSUser get(int id) {
        return ymsservice.getUserById(int id);
    }

    public YMSUser updatePassword(YMSUser paUser, String paNewPassword) {
        if(paNewPassword.length < 12) {
            throw new PasswordLengthInvalidException();
        }

        if( ! paNewPassword.startsWith('A') ) {
            throw new PasswordValidationException();
        }

        ymsService.updatePassword(paNewPassword);
        return paUser;
    }
}