BEFORE.java

AFTER.java

    @Override
    protected void defineConverter(ConverterBuilder<User, UserDTO> builder, Converter converter) {
        builder
                .convertEntity((entity, dto) -> dto.getRoles().addAll(entity.getRoles().stream()
                        .map(x -> converter.convert(x, RoleDTO.class))
                        .collect(Collectors.toSet())))
                .convertDto((dto, entity) -> entity.setRoles(dto.getRoles().stream()
                        .map(x -> converter.convert(x, Role.class))
                        .collect(Collectors.toSet())));
    }

BEFORE.java

    @Override
    protected DTOConverter<User, UserDTO> defineConverter(ModelMapper mapper, Class<User> user, Class<UserDTO> dto) {
        return new CustomConverterDTO<User, UserDTO>(mapper, user, dto) {
            @Override
            public User fromDto(UserDTO dto) {
                return getEntity(dto).setRoles(dto.getRoles().stream()
                        .map(x -> convert(x, Role.class))
                        .collect(Collectors.toSet()));
            }

            @Override
            public UserDTO fromEntity(User entity) {
                UserDTO dto = getDto(entity);

                dto.getRoles().addAll(entity.getRoles().stream()
                        .map(x -> convert(x, RoleDTO.class))
                        .collect(Collectors.toSet()));
                return dto;
            }
        };
    }