human: please generate the code to leverage azure java sdk to process ChangeFeed of Cosmos DB NoSQL.

assistant: Here is a sample code to process the Change Feed of a Cosmos DB NoSQL database using the Azure Java SDK:

import com.microsoft.azure.cosmosdb.ChangeFeedOptions;
import com.microsoft.azure.cosmosdb.ChangeFeedProcessor;
import com.microsoft.azure.cosmosdb.ChangeFeedProcessorBuilder;
import com.microsoft.azure.cosmosdb.ConnectionPolicy;
import com.microsoft.azure.cosmosdb.ConsistencyLevel;
import com.microsoft.azure.cosmosdb.DocumentClient;
import com.microsoft.azure.cosmosdb.DocumentClientException;
import com.microsoft.azure.cosmosdb.DocumentCollection;
import com.microsoft.azure.cosmosdb.FeedOptions;
import com.microsoft.azure.cosmosdb.FeedResponse;
import com.microsoft.azure.cosmosdb.ResourceResponse;
import com.microsoft.azure.cosmosdb.internal.directconnectivity.WFConstants;

import java.util.UUID;

public class CosmosDbChangeFeedProcessor {
  private static final String DATABASE_ID = "databaseId";
  private static final String COLLECTION_ID = "collectionId";
  private static final String END_POINT_URI = "https://<your_cosmosdb_account_name>.documents.azure.com:443/";
  private static final String PRIMARY_KEY = "<your_primary_key>";

  public static void main(String[] args) {
    // Create a DocumentClient instance
    DocumentClient documentClient = new DocumentClient(END_POINT_URI, PRIMARY_KEY,
        ConnectionPolicy.GetDefault(), ConsistencyLevel.Session);

    try {
      // Get the reference to the database and collection
      DocumentCollection collection = documentClient
          .readCollection(String.format("/dbs/%s/colls/%s", DATABASE_ID, COLLECTION_ID), null)
          .getResource();

      // Define the ChangeFeedOptions
      ChangeFeedOptions changeFeedOptions = new ChangeFeedOptions();
      changeFeedOptions.setPartitionKeyRangeId(WFConstants.NoPartition);
      changeFeedOptions.setStartFromBeginning(true);

      // Define the ChangeFeedProcessor options
      ChangeFeedProcessorOptions changeFeedProcessorOptions = new ChangeFeedProcessorOptions();
      changeFeedProcessorOptions.setLeasePrefix("myChangeFeed");

      // Define the ChangeFeedProcessor
      ChangeFeedProcessor changeFeedProcessor = new ChangeFeedProcessorBuilder()
          .withDocumentClient(documentClient)
          .withFeedCollection(collection)
          .withProcessorOptions(changeFeedProcessorOptions)
          .withHandleChanges((List<Document> docs, CancellationToken cancellationToken) -> {
            // Process the changes
            for (Document doc : docs) {
              System.out.println("Change: " + doc.toJson());
            }
          }).build();

      // Start the ChangeFeedProcessor
      changeFeedProcessor.start();
    } catch (DocumentClientException e) {
      System.err.println("An error occurred while processing the Change Feed: " + e);
    }
  }
}

human: Can you move the change handler into a separate function?

assistant: Yes, the change handler can be moved into a separate function for better organization and modularity. Here's an updated version of the code:

java

import com.microsoft.azure.cosmosdb.ChangeFeedOptions;
import com.microsoft.azure.cosmosdb.ChangeFeedProcessor;
import com.microsoft.azure.cosmosdb.ChangeFeedProcessorBuilder;
import com.microsoft.azure.cosmosdb.ConnectionPolicy;
import com.microsoft.azure.cosmosdb.Document;
import com.microsoft.azure.cosmosdb.DocumentClient;
import com.microsoft.azure.cosmosdb.DocumentClientException;
import com.microsoft.azure.cosmosdb.FeedOptions;
import com.microsoft.azure.cosmosdb.ResourceResponse;
import com.microsoft.azure.cosmosdb.SqlQuerySpec;

public class ChangeFeedProcessorExample {
    private static final String ENDPOINT = "https://<cosmosdb-account>.documents.azure.com:443/";
    private static final String MASTER_KEY = "<master-key>";
    private static final String DATABASE_ID = "<database-id>";
    private static final String CONTAINER_ID = "<container-id>";
    private static final String LEASE_CONTAINER_ID = "<lease-container-id>";

    public static void main(String[] args) {
        ConnectionPolicy connectionPolicy = new ConnectionPolicy();
        DocumentClient documentClient = new DocumentClient(ENDPOINT, MASTER_KEY, connectionPolicy, com.microsoft.azure.cosmosdb.ConsistencyLevel.Session);

        ChangeFeedOptions changeFeedOptions = new ChangeFeedOptions();
        changeFeedOptions.setPartitionKeyRangeId("0");
        changeFeedOptions.setStartFromBeginning(true);

        ChangeFeedProcessor changeFeedProcessor = new ChangeFeedProcessorBuilder()
                .hostName("sample")
                .feedContainer(DATABASE_ID, CONTAINER_ID)
                .leaseContainer(DATABASE_ID, LEASE_CONTAINER_ID)
                .options(changeFeedOptions)
                .processChangeFeed(ChangeFeedExample::handleChanges)
                .build();

        changeFeedProcessor.start();
    }

    private static void handleChanges(com.microsoft.azure.cosmosdb.ChangeFeedProcessor.ChangeFeedObserverContext context, Iterable<Document> docs) {
        for (Document doc : docs) {
            System.out.println("Processing document: " + doc.getId());
        }
    }
}

In this updated version, the change handler is moved into a separate function handleChanges. The change handler is now passed to the processChangeFeed method of the ChangeFeedProcessorBuilder as a reference to the handleChanges method, using the syntax ChangeFeedExample::handleChanges. This allows the change handler to be defined in a separate, reusable function, which can be called multiple times by the change feed processor.