With Graph SDK v6.1 MS introduced the new PageIterator class to iterate over collection objects. We need this new feature for a lot of different collection types. Because of this, I would like to create a generic paging function, that can iterate over all different collections. But I was not able, to implement it satisfyingly. I see the following things, I would like to improve:

• We have to write the query configuration twice – once for the first query and a second time for the PageIterator
• Every Response Type has explicitly to be added in the PageIterator’s collectionPageFactory

Does someone have the same problem or/and have Ideas to improve our current solution?

Our code looks like this:

@Suppress("UNCHECKED_CAST")
fun getServicePrincipals(): List<ServicePrincipal> {
    try {
        val servicePrincipalCollectionResponse = graphServiceClient.servicePrincipals().get { requestConfiguration ->
            requestConfiguration.queryParameters.select = arrayOf(SERVICE_PRINCIPALS_SELECT_PARAMETER)
            requestConfiguration.queryParameters.top = azureConfig.pagingPageSize
        }

        val requestInformationMap: Map<String, Any> = mapOf(
            "%24select" to arrayOf(SERVICE_PRINCIPALS_SELECT_PARAMETER),
            "%24top" to azureConfig.pagingPageSize
        )

        return getResponseOfAllPages(servicePrincipalCollectionResponse, requestInformationMap) as List<ServicePrincipal>
    } catch (e: ApiException) {
        log.error("Error while getting servicePrincipals: ${e.message}")
        return emptyList()
    }
}

private fun getResponseOfAllPages(baseCollectionPaginationCountResponse: BaseCollectionPaginationCountResponse, requestInformationMap: Map<String, Any>): List<Entity> {
    val entities = mutableListOf<Entity>()

    val pageIterator = PageIterator.Builder<Entity, BaseCollectionPaginationCountResponse>()
        .client(graphServiceClient)
        .collectionPage(baseCollectionPaginationCountResponse)
        .collectionPageFactory(
            when (baseCollectionPaginationCountResponse) {
                is ApplicationCollectionResponse -> ApplicationCollectionResponse::createFromDiscriminatorValue
                is DirectoryObjectCollectionResponse -> DirectoryObjectCollectionResponse::createFromDiscriminatorValue
                is AppRoleAssignmentCollectionResponse -> AppRoleAssignmentCollectionResponse::createFromDiscriminatorValue
                is ServicePrincipalCollectionResponse -> ServicePrincipalCollectionResponse::createFromDiscriminatorValue
                else -> throw IllegalArgumentException("No response of type ApplicationCollectionResponse, DirectoryObjectCollectionResponse, AppRoleAssignmentCollectionResponse, ServicePrincipalCollectionResponse found. Please implement handling any other type.")
            }
        )
        .processPageItemCallback { entities.add(it) }
        .requestConfigurator { requestInformation ->
            requestInformationMap.forEach {
                requestInformation.addQueryParameter(it.key, it.value)
            }
            requestInformation
        }
        .build()

    pageIterator.iterate()

    return entities
}