Generic code to wrap lambdas into a common pattern

wrap.java

public class WrapperUser extends AbstractEndpoint{
  public doWrappedOperation(){
    return wrap(user, appUser -> new ApiUpdateList(updateService.list(appUser, exportId, limit, pageToken)));
  }
}



public class AbstractEndpoint { //should be abstract, but prevents discovery generation if not

    private StoreService storeService = new StoreService();

    protected interface ApiTask<T> {
        T apply(AppUser user) throws ServiceException, ApiException;
    }

    protected <T> T wrap(User user, ApiTask<T> action) throws ServiceException {
        Preconditions.checkNotNull(user, "Please use OAuth2 to authenticate").getEmail();

        AppUser appUser = storeService.load(AppUser.class, user.getId())
                .orElseThrow(() -> new UnauthorizedException("User not recognized"));

        try {
            return action.apply(appUser);
        } catch (UnauthorizedException e) {
            throw new UnauthorizedException(e.getMessage(), e);
        } catch (ForbiddenException e) {
            throw new ForbiddenException(e.getMessage(), e);
        } catch (NotFoundException e) {
            throw new NotFoundException(e.getMessage(), e);
        } catch (BadRequestException e) {
            throw new BadRequestException(e.getMessage(), e);
        } catch (ConflictException e) {
            throw new ConflictException(e.getMessage(), e);
        } catch (ApiException e) {
            throw Throwables.propagate(e);
        }
    }
}