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azure-eventhub-java skill

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This skill helps you implement real-time Azure Event Hubs workflows in Java, enabling high-throughput streaming and reliable event processing.

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---
name: azure-eventhub-java
description: Build real-time streaming applications with Azure Event Hubs SDK for Java. Use when implementing event streaming, high-throughput data ingestion, or building event-driven architectures.
package: com.azure:azure-messaging-eventhubs
---

# Azure Event Hubs SDK for Java

Build real-time streaming applications using the Azure Event Hubs SDK for Java.

## Installation

```xml
<dependency>
    <groupId>com.azure</groupId>
    <artifactId>azure-messaging-eventhubs</artifactId>
    <version>5.19.0</version>
</dependency>

<!-- For checkpoint store (production) -->
<dependency>
    <groupId>com.azure</groupId>
    <artifactId>azure-messaging-eventhubs-checkpointstore-blob</artifactId>
    <version>1.20.0</version>
</dependency>
```

## Client Creation

### EventHubProducerClient

```java
import com.azure.messaging.eventhubs.EventHubProducerClient;
import com.azure.messaging.eventhubs.EventHubClientBuilder;

// With connection string
EventHubProducerClient producer = new EventHubClientBuilder()
    .connectionString("<connection-string>", "<event-hub-name>")
    .buildProducerClient();

// Full connection string with EntityPath
EventHubProducerClient producer = new EventHubClientBuilder()
    .connectionString("<connection-string-with-entity-path>")
    .buildProducerClient();
```

### With DefaultAzureCredential

```java
import com.azure.identity.DefaultAzureCredentialBuilder;

EventHubProducerClient producer = new EventHubClientBuilder()
    .fullyQualifiedNamespace("<namespace>.servicebus.windows.net")
    .eventHubName("<event-hub-name>")
    .credential(new DefaultAzureCredentialBuilder().build())
    .buildProducerClient();
```

### EventHubConsumerClient

```java
import com.azure.messaging.eventhubs.EventHubConsumerClient;

EventHubConsumerClient consumer = new EventHubClientBuilder()
    .connectionString("<connection-string>", "<event-hub-name>")
    .consumerGroup(EventHubClientBuilder.DEFAULT_CONSUMER_GROUP_NAME)
    .buildConsumerClient();
```

### Async Clients

```java
import com.azure.messaging.eventhubs.EventHubProducerAsyncClient;
import com.azure.messaging.eventhubs.EventHubConsumerAsyncClient;

EventHubProducerAsyncClient asyncProducer = new EventHubClientBuilder()
    .connectionString("<connection-string>", "<event-hub-name>")
    .buildAsyncProducerClient();

EventHubConsumerAsyncClient asyncConsumer = new EventHubClientBuilder()
    .connectionString("<connection-string>", "<event-hub-name>")
    .consumerGroup("$Default")
    .buildAsyncConsumerClient();
```

## Core Patterns

### Send Single Event

```java
import com.azure.messaging.eventhubs.EventData;

EventData eventData = new EventData("Hello, Event Hubs!");
producer.send(Collections.singletonList(eventData));
```

### Send Event Batch

```java
import com.azure.messaging.eventhubs.EventDataBatch;
import com.azure.messaging.eventhubs.models.CreateBatchOptions;

// Create batch
EventDataBatch batch = producer.createBatch();

// Add events (returns false if batch is full)
for (int i = 0; i < 100; i++) {
    EventData event = new EventData("Event " + i);
    if (!batch.tryAdd(event)) {
        // Batch is full, send and create new batch
        producer.send(batch);
        batch = producer.createBatch();
        batch.tryAdd(event);
    }
}

// Send remaining events
if (batch.getCount() > 0) {
    producer.send(batch);
}
```

### Send to Specific Partition

```java
CreateBatchOptions options = new CreateBatchOptions()
    .setPartitionId("0");

EventDataBatch batch = producer.createBatch(options);
batch.tryAdd(new EventData("Partition 0 event"));
producer.send(batch);
```

### Send with Partition Key

```java
CreateBatchOptions options = new CreateBatchOptions()
    .setPartitionKey("customer-123");

EventDataBatch batch = producer.createBatch(options);
batch.tryAdd(new EventData("Customer event"));
producer.send(batch);
```

### Event with Properties

```java
EventData event = new EventData("Order created");
event.getProperties().put("orderId", "ORD-123");
event.getProperties().put("customerId", "CUST-456");
event.getProperties().put("priority", 1);

producer.send(Collections.singletonList(event));
```

### Receive Events (Simple)

```java
import com.azure.messaging.eventhubs.models.EventPosition;
import com.azure.messaging.eventhubs.models.PartitionEvent;

// Receive from specific partition
Iterable<PartitionEvent> events = consumer.receiveFromPartition(
    "0",                           // partitionId
    10,                            // maxEvents
    EventPosition.earliest(),      // startingPosition
    Duration.ofSeconds(30)         // timeout
);

for (PartitionEvent partitionEvent : events) {
    EventData event = partitionEvent.getData();
    System.out.println("Body: " + event.getBodyAsString());
    System.out.println("Sequence: " + event.getSequenceNumber());
    System.out.println("Offset: " + event.getOffset());
}
```

### EventProcessorClient (Production)

```java
import com.azure.messaging.eventhubs.EventProcessorClient;
import com.azure.messaging.eventhubs.EventProcessorClientBuilder;
import com.azure.messaging.eventhubs.checkpointstore.blob.BlobCheckpointStore;
import com.azure.storage.blob.BlobContainerAsyncClient;
import com.azure.storage.blob.BlobContainerClientBuilder;

// Create checkpoint store
BlobContainerAsyncClient blobClient = new BlobContainerClientBuilder()
    .connectionString("<storage-connection-string>")
    .containerName("checkpoints")
    .buildAsyncClient();

// Create processor
EventProcessorClient processor = new EventProcessorClientBuilder()
    .connectionString("<eventhub-connection-string>", "<event-hub-name>")
    .consumerGroup("$Default")
    .checkpointStore(new BlobCheckpointStore(blobClient))
    .processEvent(eventContext -> {
        EventData event = eventContext.getEventData();
        System.out.println("Processing: " + event.getBodyAsString());
        
        // Checkpoint after processing
        eventContext.updateCheckpoint();
    })
    .processError(errorContext -> {
        System.err.println("Error: " + errorContext.getThrowable().getMessage());
        System.err.println("Partition: " + errorContext.getPartitionContext().getPartitionId());
    })
    .buildEventProcessorClient();

// Start processing
processor.start();

// Keep running...
Thread.sleep(Duration.ofMinutes(5).toMillis());

// Stop gracefully
processor.stop();
```

### Batch Processing

```java
EventProcessorClient processor = new EventProcessorClientBuilder()
    .connectionString("<connection-string>", "<event-hub-name>")
    .consumerGroup("$Default")
    .checkpointStore(new BlobCheckpointStore(blobClient))
    .processEventBatch(eventBatchContext -> {
        List<EventData> events = eventBatchContext.getEvents();
        System.out.printf("Received %d events%n", events.size());
        
        for (EventData event : events) {
            // Process each event
            System.out.println(event.getBodyAsString());
        }
        
        // Checkpoint after batch
        eventBatchContext.updateCheckpoint();
    }, 50) // maxBatchSize
    .processError(errorContext -> {
        System.err.println("Error: " + errorContext.getThrowable());
    })
    .buildEventProcessorClient();
```

### Async Receiving

```java
asyncConsumer.receiveFromPartition("0", EventPosition.latest())
    .subscribe(
        partitionEvent -> {
            EventData event = partitionEvent.getData();
            System.out.println("Received: " + event.getBodyAsString());
        },
        error -> System.err.println("Error: " + error),
        () -> System.out.println("Complete")
    );
```

### Get Event Hub Properties

```java
// Get hub info
EventHubProperties hubProps = producer.getEventHubProperties();
System.out.println("Hub: " + hubProps.getName());
System.out.println("Partitions: " + hubProps.getPartitionIds());

// Get partition info
PartitionProperties partitionProps = producer.getPartitionProperties("0");
System.out.println("Begin sequence: " + partitionProps.getBeginningSequenceNumber());
System.out.println("Last sequence: " + partitionProps.getLastEnqueuedSequenceNumber());
System.out.println("Last offset: " + partitionProps.getLastEnqueuedOffset());
```

## Event Positions

```java
// Start from beginning
EventPosition.earliest()

// Start from end (new events only)
EventPosition.latest()

// From specific offset
EventPosition.fromOffset(12345L)

// From specific sequence number
EventPosition.fromSequenceNumber(100L)

// From specific time
EventPosition.fromEnqueuedTime(Instant.now().minus(Duration.ofHours(1)))
```

## Error Handling

```java
import com.azure.messaging.eventhubs.models.ErrorContext;

.processError(errorContext -> {
    Throwable error = errorContext.getThrowable();
    String partitionId = errorContext.getPartitionContext().getPartitionId();
    
    if (error instanceof AmqpException) {
        AmqpException amqpError = (AmqpException) error;
        if (amqpError.isTransient()) {
            System.out.println("Transient error, will retry");
        }
    }
    
    System.err.printf("Error on partition %s: %s%n", partitionId, error.getMessage());
})
```

## Resource Cleanup

```java
// Always close clients
try {
    producer.send(batch);
} finally {
    producer.close();
}

// Or use try-with-resources
try (EventHubProducerClient producer = new EventHubClientBuilder()
        .connectionString(connectionString, eventHubName)
        .buildProducerClient()) {
    producer.send(events);
}
```

## Environment Variables

```bash
EVENT_HUBS_CONNECTION_STRING=Endpoint=sb://<namespace>.servicebus.windows.net/;SharedAccessKeyName=...
EVENT_HUBS_NAME=<event-hub-name>
STORAGE_CONNECTION_STRING=<for-checkpointing>
```

## Best Practices

1. **Use EventProcessorClient**: For production, provides load balancing and checkpointing
2. **Batch Events**: Use `EventDataBatch` for efficient sending
3. **Partition Keys**: Use for ordering guarantees within a partition
4. **Checkpointing**: Checkpoint after processing to avoid reprocessing
5. **Error Handling**: Handle transient errors with retries
6. **Close Clients**: Always close producer/consumer when done

## Trigger Phrases

- "Event Hubs Java"
- "event streaming Azure"
- "real-time data ingestion"
- "EventProcessorClient"
- "event hub producer consumer"
- "partition processing"

Overview

This skill shows how to build real-time streaming applications using the Azure Event Hubs SDK for Java. It focuses on creating producers and consumers (sync and async), reliable processing with EventProcessorClient, and practical patterns for batching, partitioning, and checkpointing. The goal is fast, scalable ingestion and robust event-driven architectures.

How this skill works

The examples demonstrate creating EventHubProducerClient and EventHubConsumerClient (and their async variants) both with connection strings and DefaultAzureCredential. It inspects core patterns: sending single events, batching with EventDataBatch, targeting partitions or partition keys, and receiving via simple consumers or the EventProcessorClient with blob checkpoint storage. Error handling, event positions, and resource cleanup are shown to make production usage resilient.

When to use it

Implement high-throughput event ingestion pipelines
Build real-time analytics or telemetry collectors
Implement event-driven microservices and stream processing
Maintain ordered processing per customer or key using partitions
Deploy production consumers with automatic load balancing and checkpointing

Best practices

Use EventProcessorClient for production to get load balancing and checkpointing
Batch events with EventDataBatch to improve throughput and lower costs
Use partition keys for ordering guarantees within a partition
Checkpoint after successful processing to avoid duplicate work
Handle transient AMQP errors with retries and log partition context
Always close clients or use try-with-resources to free connections

Example use cases

Telemetry pipeline that ingests device metrics and writes to blob or analytics store
Order processing stream where events for a customer use a partition key for ordering
Real-time dashboard fed by an async consumer that subscribes to latest events
Backfill or replay using specific EventPosition (earliest, offset, or timestamp)
High-availability event handlers using EventProcessorClient with Azure Blob checkpoint store

FAQ

Which client should I use in production, sync or async?

Use EventProcessorClient for production consumers because it provides automatic partition load balancing and checkpointing. Use async clients when you need non-blocking processing and reactive backpressure handling.

How do I ensure ordered processing for a single customer?

Send events with a partition key (setPartitionKey) or target a specific partition. Events with the same partition key route to the same partition, preserving order.

How should I handle failures to avoid data loss?

Checkpoint only after successful processing. Combine retries for transient errors with durable checkpoint storage (e.g., BlobCheckpointStore) so unprocessed events can be retried after restarts.