ODATA: How to get list of users using '@odata.nextLink' about odata-client

[madanbisht]

Hi David,
We have verified and its working perfectly.

We sincerely appreciate your consideration and time for developing this to us so quickly...!!!

[davidmoten]

Why do you care about low-level stuff like @odata.nextLink? Just use the collections support in the API. See Collections and paging in the README.md. Can you explain your use case further?

[madanbisht]

Thanks for your response and below is the use-case:

There is a service which receives request from a client and we are trying to implement paging, so that the service will send only the list of users requested by the client. As an example:

Step 1) Client send request to get the list of N users and service can get user-list as below:

     OdataClientFactory
                    .request()
                    .users().top(N)
                    .get();

After getting response client will parse N users and extract @data.nextLink from the response.

Step 2) Client sends request to get next N users providing the @data.nextLink and service can use @data.nextLink to get next N users.

After getting response client will parse the user-list and extract @data.nextLink from the response.

Step 3) Repetition of step 2.

[davidmoten]

So you're sort of proxying the Graph API for the client? @odata.nextLink just uses a skip field. You could add a counter field to the returned JSON and then get the user to pass the last counter value to the service instead of @odata.nextLink and use

List<User> page = client.client.users().skip(counter).get().currentPage();

when they call the service. That way you are not coupled to odata metadata like @odata.nextLink.

I could probably provide access to the @odata.nextLink field, I just wanted to explore alternatives first.

Note also you could parse the @odata.nextLink field that the client gives you for the skip parameter and use that in the call above.

[madanbisht]

We already tried skip option(as given below) but as soon as we use skip it throws an exception(java.lang.NullPointerException). It seems skip is not supported.

List<User> users = OdataClientFactory
                    .request()
                    .users().skip(1)
                    .get()
                    .currentPage();

Ideally our use case can be implemented with below code, here top works fine but as soon as we use skip it throws exception.

List<User> users = OdataClientFactory
                    .request()
                    .users().top(200).skip(100)
                    .get()
                    .currentPage();

[davidmoten]

Can you supply full stack trace? An NPE sounds like something I have to fix.

[davidmoten]

By the way if top is your attempt to control page size I don't think it works.

[davidmoten]

I just tried client.users().top(200).skip(100).get().currentPage() and like you I got an NPE. I'll fix that. However the base cause is

10:44:32.468 [main] DEBUG com.github.davidmoten.odata.client.internal.ApacheHttpClientHttpService - response text=
{
  "error": {
    "code": "Request_BadRequest",
    "message": "'$skip' is not supported by the service.",
    "innerError": {
      "date": "2020-06-13T00:44:32",
      "request-id": "63ed6165-729f-4753-88b9-e67399a312f5"
    }
  }
}

[davidmoten]

In fact, digging a bit deeper I don't even have privileges:

client.users().stream().forEach(user -> System.out.println(user.getPrincipalName()));

gives an NPE (something else to fix!) and log says:

{
  "error": {
    "code": "Authorization_RequestDenied",
    "message": "Insufficient privileges to complete the operation.",
    "innerError": {
      "date": "2020-06-13T00:48:55",
      "request-id": "31c91f39-f97b-4f8b-8f6f-c4c00c1a8fe9"
    }
  }
}

[davidmoten]

Reading a bit further I think the collection returned by users().get() must use $skipToken for pagination instead of $skip. Given this I need to rethink the advice about using skip.

[davidmoten]

Please review PR #17.

[davidmoten]

I've addressed this issue now with #17.

You can specify the link for a collection like this:

List<User> users = client.users().urlOverride(url).get().currentPage();

I'll release shortly, let me know if any problems.

[davidmoten]

0.1.16 released to Maven Central with #16, #17 that resolve this issue. You may wish to watch this repository to hear about future releases (which are pretty frequent lately).