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# Iscriviti a Amazon Kinesis Data Streams
<a name="examples-kinesis-stream"></a>

Gli esempi seguenti mostrano come recuperare ed elaborare i Amazon Kinesis dati da Data Streams utilizzando il metodo. `subscribeToShard` Kinesis Data Streams ora utilizza la funzionalità fanout avanzata e un'API di recupero dati HTTP/2 a bassa latenza, che facilita agli sviluppatori l'esecuzione di più applicazioni a bassa latenza e ad alte prestazioni sullo stesso Data Stream. Kinesis 

## Configurazione
<a name="set-up"></a>

Innanzitutto, [SubscribeToShardRequest](https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/kinesis/model/SubscribeToShardRequest.html)crea un client asincrono e un oggetto. Kinesis Questi oggetti vengono utilizzati in ciascuno degli esempi seguenti per sottoscrivere gli eventi. Kinesis 

 **Importazioni** 

```
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.atomic.AtomicInteger;
import org.reactivestreams.Subscriber;
import org.reactivestreams.Subscription;
import software.amazon.awssdk.core.async.SdkPublisher;
import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.kinesis.KinesisAsyncClient;
import software.amazon.awssdk.services.kinesis.model.ShardIteratorType;
import software.amazon.awssdk.services.kinesis.model.SubscribeToShardEvent;
import software.amazon.awssdk.services.kinesis.model.SubscribeToShardEventStream;
import software.amazon.awssdk.services.kinesis.model.SubscribeToShardRequest;
import software.amazon.awssdk.services.kinesis.model.SubscribeToShardResponse;
import software.amazon.awssdk.services.kinesis.model.SubscribeToShardResponseHandler;
```

 **Codice** 

```
        Region region = Region.US_EAST_1;
        KinesisAsyncClient client = KinesisAsyncClient.builder()
        .region(region)
        .build();

        SubscribeToShardRequest request = SubscribeToShardRequest.builder()
                .consumerARN(CONSUMER_ARN)
                .shardId("arn:aws:kinesis:us-east-1:111122223333:stream/StockTradeStream")
                .startingPosition(s -> s.type(ShardIteratorType.LATEST)).build();
```

## Usa l'interfaccia Builder
<a name="use-the-builder-interface"></a>

È possibile utilizzare il `builder` metodo per semplificare la creazione di. [SubscribeToShardResponseHandler](https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/kinesis/model/SubscribeToShardResponseHandler.html)

Utilizzando il generatore, è possibile impostare la richiamata del ciclo di vita con una chiamata al metodo invece che implementando l'interfaccia completa.

 **Codice** 

```
    private static CompletableFuture<Void> responseHandlerBuilder(KinesisAsyncClient client, SubscribeToShardRequest request) {
        SubscribeToShardResponseHandler responseHandler = SubscribeToShardResponseHandler
                .builder()
                .onError(t -> System.err.println("Error during stream - " + t.getMessage()))
                .onComplete(() -> System.out.println("All records stream successfully"))
                // Must supply some type of subscriber
                .subscriber(e -> System.out.println("Received event - " + e))
                .build();
        return client.subscribeToShard(request, responseHandler);
    }
```

Per un maggiore controllo del publisher, è possibile utilizzare il metodo `publisherTransformer` per personalizzare il publisher.

 **Codice** 

```
    private static CompletableFuture<Void> responseHandlerBuilderPublisherTransformer(KinesisAsyncClient client, SubscribeToShardRequest request) {
        SubscribeToShardResponseHandler responseHandler = SubscribeToShardResponseHandler
                .builder()
                .onError(t -> System.err.println("Error during stream - " + t.getMessage()))
                .publisherTransformer(p -> p.filter(e -> e instanceof SubscribeToShardEvent).limit(100))
                .subscriber(e -> System.out.println("Received event - " + e))
                .build();
        return client.subscribeToShard(request, responseHandler);
    }
```

Vedi l'[esempio completo](https://github.com/awsdocs/aws-doc-sdk-examples/blob/ac748d8ef99cd17e297cb74fe13aa671e2679088/javav2/example_code/kinesis/src/main/java/com/example/kinesis/KinesisStreamEx.java) su GitHub.

## Usa un gestore di risposte personalizzato
<a name="use-a-custom-response-handler"></a>

Per il pieno controllo dell'abbonato e dell'editore, implementa l'`SubscribeToShardResponseHandler`interfaccia.

In questo esempio implementi il metodo `onEventStream`, che ti consente l'accesso completo al publisher. Questo dimostra come trasformare il publisher in record di eventi da stampare da parte del sottoscrittore.

 **Codice** 

```
    private static CompletableFuture<Void> responseHandlerBuilderClassic(KinesisAsyncClient client, SubscribeToShardRequest request) {
        SubscribeToShardResponseHandler responseHandler = new SubscribeToShardResponseHandler() {

            @Override
            public void responseReceived(SubscribeToShardResponse response) {
                System.out.println("Receieved initial response");
            }

            @Override
            public void onEventStream(SdkPublisher<SubscribeToShardEventStream> publisher) {
                publisher
                        // Filter to only SubscribeToShardEvents
                        .filter(SubscribeToShardEvent.class)
                        // Flat map into a publisher of just records
                        .flatMapIterable(SubscribeToShardEvent::records)
                        // Limit to 1000 total records
                        .limit(1000)
                        // Batch records into lists of 25
                        .buffer(25)
                        // Print out each record batch
                        .subscribe(batch -> System.out.println("Record Batch - " + batch));
            }

            @Override
            public void complete() {
                System.out.println("All records stream successfully");
            }

            @Override
            public void exceptionOccurred(Throwable throwable) {
                System.err.println("Error during stream - " + throwable.getMessage());
            }
        };
        return client.subscribeToShard(request, responseHandler);
    }
```

Vedi l'[esempio completo](https://github.com/awsdocs/aws-doc-sdk-examples/blob/ac748d8ef99cd17e297cb74fe13aa671e2679088/javav2/example_code/kinesis/src/main/java/com/example/kinesis/KinesisStreamEx.java) su. GitHub

## Usa l'interfaccia per i visitatori
<a name="use-the-visitor-interface"></a>

È possibile utilizzare un oggetto [Visitatore](https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/kinesis/model/SubscribeToShardResponseHandler.Visitor.html) per iscriverti a eventi specifici che ti interessa guardare.

 **Codice** 

```
    private static CompletableFuture<Void> responseHandlerBuilderVisitorBuilder(KinesisAsyncClient client, SubscribeToShardRequest request) {
        SubscribeToShardResponseHandler.Visitor visitor = SubscribeToShardResponseHandler.Visitor
                .builder()
                .onSubscribeToShardEvent(e -> System.out.println("Received subscribe to shard event " + e))
                .build();
        SubscribeToShardResponseHandler responseHandler = SubscribeToShardResponseHandler
                .builder()
                .onError(t -> System.err.println("Error during stream - " + t.getMessage()))
                .subscriber(visitor)
                .build();
        return client.subscribeToShard(request, responseHandler);
    }
```

Guarda l'[esempio completo](https://github.com/awsdocs/aws-doc-sdk-examples/blob/ac748d8ef99cd17e297cb74fe13aa671e2679088/javav2/example_code/kinesis/src/main/java/com/example/kinesis/KinesisStreamEx.java) su GitHub.

## Usa un abbonato personalizzato
<a name="use-a-custom-subscriber"></a>

Puoi anche implementare i tuoi sottoscrittori personalizzati per iscriverti al flusso.

Questo frammento di codice mostra un esempio di sottoscrittore.

 **Codice** 

```
    private static class MySubscriber implements Subscriber<SubscribeToShardEventStream> {

        private Subscription subscription;
        private AtomicInteger eventCount = new AtomicInteger(0);

        @Override
        public void onSubscribe(Subscription subscription) {
            this.subscription = subscription;
            this.subscription.request(1);
        }

        @Override
        public void onNext(SubscribeToShardEventStream shardSubscriptionEventStream) {
            System.out.println("Received event " + shardSubscriptionEventStream);
            if (eventCount.incrementAndGet() >= 100) {
                // You can cancel the subscription at any time if you wish to stop receiving events.
                subscription.cancel();
            }
            subscription.request(1);
        }

        @Override
        public void onError(Throwable throwable) {
            System.err.println("Error occurred while stream - " + throwable.getMessage());
        }

        @Override
        public void onComplete() {
            System.out.println("Finished streaming all events");
        }
    }
```

È possibile passare l'abbonato personalizzato al `subscribe` metodo come illustrato nel seguente frammento di codice.

 **Codice** 

```
    private static CompletableFuture<Void> responseHandlerBuilderSubscriber(KinesisAsyncClient client, SubscribeToShardRequest request) {
        SubscribeToShardResponseHandler responseHandler = SubscribeToShardResponseHandler
                .builder()
                .onError(t -> System.err.println("Error during stream - " + t.getMessage()))
                .subscriber(MySubscriber::new)
                .build();
        return client.subscribeToShard(request, responseHandler);
    }
```

Vedi l'esempio [completo](https://github.com/awsdocs/aws-doc-sdk-examples/blob/ac748d8ef99cd17e297cb74fe13aa671e2679088/javav2/example_code/kinesis/src/main/java/com/example/kinesis/KinesisStreamEx.java) su. GitHub

## Scrivi i record di dati in un flusso di Kinesis dati
<a name="write-data-records-into-a-kinesis-data-stream"></a>

È possibile utilizzare l'[KinesisClient](https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/kinesis/KinesisClient.html)oggetto per scrivere record di dati in un flusso di Kinesis dati utilizzando il `putRecords` metodo. Per richiamare correttamente questo metodo, create un [PutRecordsRequest](https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/kinesis/model/PutRecordsRequest.html)oggetto. Si passa il nome del flusso di dati al `streamName` metodo. Inoltre devi passare i dati utilizzando il metodo `putRecords` (come mostrato nell'esempio di codice seguente).

 **Importazioni** 

```
import software.amazon.awssdk.core.SdkBytes;
import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.kinesis.KinesisClient;
import software.amazon.awssdk.services.kinesis.model.PutRecordRequest;
import software.amazon.awssdk.services.kinesis.model.KinesisException;
import software.amazon.awssdk.services.kinesis.model.DescribeStreamRequest;
import software.amazon.awssdk.services.kinesis.model.DescribeStreamResponse;
```

Nel seguente esempio di codice Java, notate che l'**StockTrade**oggetto viene utilizzato come dati da scrivere nel flusso di Kinesis dati. Prima di eseguire questo esempio, assicuratevi di aver creato il flusso di dati.

 **Codice** 

```
import software.amazon.awssdk.core.SdkBytes;
import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.kinesis.KinesisClient;
import software.amazon.awssdk.services.kinesis.model.PutRecordRequest;
import software.amazon.awssdk.services.kinesis.model.KinesisException;
import software.amazon.awssdk.services.kinesis.model.DescribeStreamRequest;
import software.amazon.awssdk.services.kinesis.model.DescribeStreamResponse;

/**
 * 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 StockTradesWriter {
    public static void main(String[] args) {
        final String usage = """

                Usage:
                    <streamName>

                Where:
                    streamName - The Amazon Kinesis data stream to which records are written (for example, StockTradeStream)
                """;

        if (args.length != 1) {
            System.out.println(usage);
            System.exit(1);
        }

        String streamName = args[0];
        Region region = Region.US_EAST_1;
        KinesisClient kinesisClient = KinesisClient.builder()
                .region(region)
                .build();

        // Ensure that the Kinesis Stream is valid.
        validateStream(kinesisClient, streamName);
        setStockData(kinesisClient, streamName);
        kinesisClient.close();
    }

    public static void setStockData(KinesisClient kinesisClient, String streamName) {
        try {
            // Repeatedly send stock trades with a 100 milliseconds wait in between.
            StockTradeGenerator stockTradeGenerator = new StockTradeGenerator();

            // Put in 50 Records for this example.
            int index = 50;
            for (int x = 0; x < index; x++) {
                StockTrade trade = stockTradeGenerator.getRandomTrade();
                sendStockTrade(trade, kinesisClient, streamName);
                Thread.sleep(100);
            }

        } catch (KinesisException | InterruptedException e) {
            System.err.println(e.getMessage());
            System.exit(1);
        }
        System.out.println("Done");
    }

    private static void sendStockTrade(StockTrade trade, KinesisClient kinesisClient,
            String streamName) {
        byte[] bytes = trade.toJsonAsBytes();

        // The bytes could be null if there is an issue with the JSON serialization by
        // the Jackson JSON library.
        if (bytes == null) {
            System.out.println("Could not get JSON bytes for stock trade");
            return;
        }

        System.out.println("Putting trade: " + trade);
        PutRecordRequest request = PutRecordRequest.builder()
                .partitionKey(trade.getTickerSymbol()) // We use the ticker symbol as the partition key, explained in
                                                       // the Supplemental Information section below.
                .streamName(streamName)
                .data(SdkBytes.fromByteArray(bytes))
                .build();

        try {
            kinesisClient.putRecord(request);
        } catch (KinesisException e) {
            System.err.println(e.getMessage());
        }
    }

    private static void validateStream(KinesisClient kinesisClient, String streamName) {
        try {
            DescribeStreamRequest describeStreamRequest = DescribeStreamRequest.builder()
                    .streamName(streamName)
                    .build();

            DescribeStreamResponse describeStreamResponse = kinesisClient.describeStream(describeStreamRequest);

            if (!describeStreamResponse.streamDescription().streamStatus().toString().equals("ACTIVE")) {
                System.err.println("Stream " + streamName + " is not active. Please wait a few moments and try again.");
                System.exit(1);
            }

        } catch (KinesisException e) {
            System.err.println("Error found while describing the stream " + streamName);
            System.err.println(e);
            System.exit(1);
        }
    }
}
```

Vedi l'[esempio completo](https://github.com/awsdocs/aws-doc-sdk-examples/blob/master/javav2/example_code/kinesis/src/main/java/com/example/kinesis/StockTradesWriter.java) su GitHub.

## Usa una libreria di terze parti
<a name="use-a-third-party-library"></a>

Puoi utilizzare altre librerie di terze parti anziché implementare un sottoscrittore personalizzato. Questo esempio dimostra l'utilizzo dell' RxJava implementazione, ma è possibile utilizzare qualsiasi libreria che implementa le interfacce Reactive Streams. Vedi la [pagina RxJava wiki su Github per ulteriori informazioni su](https://github.com/ReactiveX/RxJava/wiki) quella libreria.

Per utilizzare la libreria, aggiungerla come una dipendenza. Se stai utilizzando Maven, l'esempio illustra lo snippet POM da utilizzare.

 **Voce POM** 

```
<dependency>
 <groupId>io.reactivex.rxjava2</groupId>
 <artifactId>rxjava</artifactId>
 <version>2.2.21</version>
</dependency>
```

 **Importazioni** 

```
import java.net.URI;
import java.util.concurrent.CompletableFuture;

import io.reactivex.Flowable;
import software.amazon.awssdk.auth.credentials.ProfileCredentialsProvider;
import software.amazon.awssdk.core.async.SdkPublisher;
import software.amazon.awssdk.http.Protocol;
import software.amazon.awssdk.http.SdkHttpConfigurationOption;
import software.amazon.awssdk.http.nio.netty.NettyNioAsyncHttpClient;
import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.kinesis.KinesisAsyncClient;
import software.amazon.awssdk.services.kinesis.model.ShardIteratorType;
import software.amazon.awssdk.services.kinesis.model.StartingPosition;
import software.amazon.awssdk.services.kinesis.model.SubscribeToShardEvent;
import software.amazon.awssdk.services.kinesis.model.SubscribeToShardRequest;
import software.amazon.awssdk.services.kinesis.model.SubscribeToShardResponseHandler;
import software.amazon.awssdk.utils.AttributeMap;
```

Questo esempio utilizza RxJava il metodo `onEventStream` lifecycle. In questo modo hai pieno accesso al publisher, che può essere utilizzato per creare un Rx Flowable.

 **Codice** 

```
        SubscribeToShardResponseHandler responseHandler = SubscribeToShardResponseHandler
            .builder()
            .onError(t -> System.err.println("Error during stream - " + t.getMessage()))
            .onEventStream(p -> Flowable.fromPublisher(p)
                                        .ofType(SubscribeToShardEvent.class)
                                        .flatMapIterable(SubscribeToShardEvent::records)
                                        .limit(1000)
                                        .buffer(25)
                                        .subscribe(e -> System.out.println("Record batch = " + e)))
            .build();
```

Puoi anche utilizzare il metodo `publisherTransformer` con il publisher `Flowable`. È necessario adattare l'`Flowable`editore a un *SdkPublisher*, come illustrato nell'esempio seguente.

 **Codice** 

```
        SubscribeToShardResponseHandler responseHandler = SubscribeToShardResponseHandler
            .builder()
            .onError(t -> System.err.println("Error during stream - " + t.getMessage()))
            .publisherTransformer(p -> SdkPublisher.adapt(Flowable.fromPublisher(p).limit(100)))
            .build();
```

Vedi l'[esempio completo](https://github.com/awsdocs/aws-doc-sdk-examples/blob/main/javav2/example_code/kinesis/src/main/java/com/example/kinesis/KinesisStreamRxJavaEx.java) su GitHub.

## Ulteriori informazioni
<a name="more-information"></a>
+  [SubscribeToShardEvent](https://docs.aws.amazon.com/kinesis/latest/APIReference/API_SubscribeToShardEvent.html)nell' Amazon Kinesis API Reference
+  [SubscribeToShard](https://docs.aws.amazon.com/kinesis/latest/APIReference/API_SubscribeToShard.html)nell' Amazon Kinesis API Reference