在Spring Security中定制身份验证

在我的Grails应用中，我使用的是Spring Security插件，并定义了一个自定义userDetailsS​​ervice Spring bean，以便控制如何检索用户和角色数据，例如

class MyUserDetailsService implements GrailsUserDetailsService {

    /**
     * Some Spring Security classes (e.g. RoleHierarchyVoter) expect at least one role, so
     * we give a user with no granted roles this one which gets past that restriction but
     * doesn't grant anything.
     */
    static final List NO_ROLES = [new GrantedAuthorityImpl(SpringSecurityUtils.NO_ROLE)]

    UserDetails loadUserByUsername(String username, boolean loadRoles) {
        return loadUserByUsername(username)
    }

    UserDetails loadUserByUsername(String username) {
        User.withTransaction { status ->

            User user = User.findByUsername(username)
            if (!user) {
                throw new UsernameNotFoundException('User not found', username)
            }

            def authorities = user.authorities.collect {new GrantedAuthorityImpl(it.authority)}
            return new CustomUserDetails(
                    user.username,
                    user.password,
                    user.enabled,
                    !user.accountExpired,
                    !user.passwordExpired,
                    !user.accountLocked,
                    authorities ?: NO_ROLES,
                    user.id,
                    user.name)
        }
    }
}

CustomUserDetails上面引用的类仅扩展GrailsUser了一个name字段：

class CustomUserDetails extends GrailsUser {

    private static final long serialVersionUID = 1;

    final String name

    CustomUserDetails(String username,
                      String password,
                      boolean enabled,
                      boolean accountNonExpired,
                      boolean credentialsNonExpired,
                      boolean accountNonLocked,
                      Collection<GrantedAuthority> authorities,
                      long id,
                      String displayName) {

        super(username, password, enabled, accountNonExpired, credentialsNonExpired, accountNonLocked, authorities, id)
        this.name = displayName
    }
}

除了自定义如何检索用户和角色数据外，我还想控制如何对用户进行身份验证。在我的情况下，身份验证过程并不像通常的“检查输入的密码是否与数据库中的密码匹配”那样简单。验证用户身份的实际细节无关紧要，因此，为简单起见，我们假设如果用户name字段与输入的密码匹配，那么他将被授予封装在中的角色（权限）CustomUserDetails。

我想插件中的某个地方可以覆盖Spring Bean，以便自定义默认身份验证机制，但是哪一个呢？因为该name字段仅由定义CustomUserDetails，所以我将需要访问返回的此类的实例MyUserDetailsService才能执行自定义身份验证，这可能吗？