Work with unsupported Data REST APIs

HERE Data SDK for C++ supports only a limited number of Data REST APIs. You can find a list of them on our page with the overall architecture.

If you need to work with any Data REST APIs that are currently not supported, you can use the olp::client::OlpClient class from our core library for the request. It has an easy-to-use interface and a retry mechanism that uses a recommended backoff strategy for subsequent requests.

The example below demonstrates how to use the olp::client::OlpClient class from the Data SDK to call the API for downloading the difference between two versions of a versioned catalog.

Example. Download the difference between two versions of a catalog.

1. Create the OlpClientSettings object.

   For instructions, see Create platform client settings.

2. Configure an OlpClient instance in one of the following ways:

   • Use the olp::client::ApiLookupClient class to perform a request and get a preconfigured olp::client::OlpClient instance.

   • Use a base URL:

     1. Get the base URL from the lookup API service.

        For instructions, see the API Lookup API Developer's Guide

     2. Create an OlpClient instance with the client settings from step 1 and the base URL.

         olp::client OlpClient client(client_settings, base_url);
        

3. Prepare the REST API request parameters and the metadata URL.

    std::multimap<std::string, std::string> header_params;
    header_params.emplace("Accept", "application/json");
   
    // Replace "my_layer" with the actual layer name.
    std::string metadata_url = "/layers/my_layer/changes";
   
    std::multimap<std::string, std::string> query_params;
   
    // Required parameters.
    query_params.emplace("startVersion", "0");
    query_params.emplace("endVersion", "1");
   
    // Optional parameters.
    query_params.emplace("additionalFields", "dataSize,checksum");
    query_params.emplace("billingTag", "Billing1234");
   
    // Can be used to cancel the ongoing request. Needs to be triggered
    // from another thread as `olp::client::OlpClient::CallApi()` is a blocking call.
    CancellationContext context;
    olp::client::HttpResponse response = client.CallApi(
        metadata_url, "GET", query_params, header_params, {}, nullptr, "", context);
   

4. Check the response and, if needed, parse JSON.

    if (response.GetStatus() != olp::http::HttpStatusCode::OK) {
        // If the response is not OK, handle error cases.
    }
   

5. If the check passed and the status of the received olp::client::HttpResponse is olp::http::HttpStatusCode::OK (that is 200 OK), extract the encoded JSON from the response and parse it using RapidJSON or any other JSON parsing library.

    std::string response_json;
    response.GetResponse(response_json);
   

   You get the information on the difference between the specified versions of the versioned catalog.