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# Hello Amazon Neptune
<a name="neptune_example_neptune_Hello_section"></a>

次のコード例は、Neptune の使用を開始する方法を示しています。

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#### [ Java ]

**SDK for Java 2.x**  
 GitHub には、その他のリソースもあります。用例一覧を検索し、[AWS コード例リポジトリ](https://github.com/awsdocs/aws-doc-sdk-examples/tree/main/javav2/example_code/neptune#code-examples)での設定と実行の方法を確認してください。

```
/**
 * Before running this Java V2 code example, set up your development
 * environment, including your credentials.
 *
 * For more information, see the following documentation topic:
 *
 * https://docs.aws.amazon.com/sdk-for-java/latest/developer-guide/get-started.html
 */
public class HelloNeptune {
    public static void main(String[] args) {
        NeptuneAsyncClient neptuneClient = NeptuneAsyncClient.create();
        describeDbCluster(neptuneClient).join(); // This ensures the async code runs to completion
    }

    /**
     * Describes the Amazon Neptune DB clusters.
     *
     * @param neptuneClient the Neptune asynchronous client used to make the request
     * @return a {@link CompletableFuture} that completes when the operation is finished
     */
    public static CompletableFuture<Void> describeDbCluster(NeptuneAsyncClient neptuneClient) {
        DescribeDbClustersRequest request = DescribeDbClustersRequest.builder()
                .maxRecords(20)
                .build();

        SdkPublisher<DescribeDbClustersResponse> paginator = neptuneClient.describeDBClustersPaginator(request);
        CompletableFuture<Void> future = new CompletableFuture<>();

        paginator.subscribe(new Subscriber<DescribeDbClustersResponse>() {
            private Subscription subscription;

            @Override
            public void onSubscribe(Subscription s) {
                this.subscription = s;
                s.request(Long.MAX_VALUE); // request all items
            }

            @Override
            public void onNext(DescribeDbClustersResponse response) {
                response.dbClusters().forEach(cluster -> {
                    System.out.println("Cluster Identifier: " + cluster.dbClusterIdentifier());
                    System.out.println("Status: " + cluster.status());
                });
            }

            @Override
            public void onError(Throwable t) {
                future.completeExceptionally(t);
            }

            @Override
            public void onComplete() {
                future.complete(null);
            }
        });

        return future.whenComplete((result, throwable) -> {
            neptuneClient.close();
            if (throwable != null) {
                System.err.println("Error describing DB clusters: " + throwable.getMessage());
            }
        });
    }
```
+  API の詳細については、「*AWS SDK for Java 2.x API リファレンス*」の「[DescribeDBClustersPaginator](https://docs.aws.amazon.com/goto/SdkForJavaV2/neptune-2014-10-31/DescribeDBClustersPaginator)」を参照してください。

------
#### [ Python ]

**SDK for Python (Boto3)**  
 GitHub には、その他のリソースもあります。用例一覧を検索し、[AWS コード例リポジトリ](https://github.com/awsdocs/aws-doc-sdk-examples/tree/main/python/example_code/neptune#code-examples)での設定と実行の方法を確認してください。

```
import boto3
from botocore.exceptions import ClientError


def describe_db_clusters(neptune_client):
    """
    Describes the Amazon Neptune DB clusters using a paginator to handle multiple pages.
    Raises ClientError with 'ResourceNotFoundException' if no clusters are found.
    """
    paginator = neptune_client.get_paginator("describe_db_clusters")
    clusters_found = False

    for page in paginator.paginate():
        for cluster in page.get("DBClusters", []):
            clusters_found = True
            print(f"Cluster Identifier: {cluster['DBClusterIdentifier']}")
            print(f"Status: {cluster['Status']}")

    if not clusters_found:
        raise ClientError(
            {
                "Error": {
                    "Code": "ResourceNotFoundException",
                    "Message": "No Neptune DB clusters found."
                }
            },
            operation_name="DescribeDBClusters"
        )

def main():
    """
    Main entry point: creates the Neptune client and calls the describe operation.
    """
    neptune_client = boto3.client("neptune")
    try:
        describe_db_clusters(neptune_client)
    except ClientError as e:
        error_code = e.response["Error"]["Code"]
        if error_code == "ResourceNotFoundException":
            print(f"Resource not found: {e.response['Error']['Message']}")
        else:
            print(f"Unexpected ClientError: {e.response['Error']['Message']}")
    except Exception as e:
        print(f"Unexpected error: {str(e)}")

if __name__ == "__main__":
    main()
```
+  API の詳細については、AWS SDK for Python (Boto3) API リファレンスの「[DescribeDBClustersPaginator](https://docs.aws.amazon.com/goto/boto3/neptune-2014-10-31/DescribeDBClustersPaginator)」を参照してください。**

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