spring boot 集成 cloud events

ask:

Integrate cloud events with spring boot, write an example, and realize event source and event target.

ChatGPT：

Ok, here is an example of integrating Cloud Events using Spring Boot, which implements event sources and event targets:

1. First, the following Maven dependencies need to be added to use Spring Cloud Stream and Cloud Events:

<dependencies>
  <dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-stream-kafka</artifactId>
  </dependency>
  <dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-stream-binder-kafka</artifactId>
  </dependency>
  <dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-stream</artifactId>
  </dependency>
  <dependency>
    <groupId>io.cloudevents</groupId>
    <artifactId>cloudevents-spring</artifactId>
    <version>2.0.2</version>
  </dependency>
</dependencies>

2. Then, create an Sourceevent source called , for sending events to a Kafka topic:

import org.springframework.cloud.stream.annotation.EnableBinding;
import org.springframework.cloud.stream.messaging.Source;
import org.springframework.messaging.support.MessageBuilder;
import org.springframework.stereotype.Component;
import io.cloudevents.spring.messaging.CloudEventMessageUtils;
import io.cloudevents.CloudEvent;
import io.cloudevents.core.builder.CloudEventBuilder;
import io.cloudevents.core.provider.EventFormatProvider;

@Component
@EnableBinding(Source.class)
public class MyEventSource {
    
    
  private final Source source;

  public MyEventSource(Source source) {
    
    
    this.source = source;
  }

  public void sendEvent(MyEventData data) {
    
    
    // 创建CloudEvent
    CloudEvent cloudEvent = CloudEventBuilder.v1()
        .withId(UUID.randomUUID().toString())
        .withType("my.event.type")
        .withSource("/my/event/source")
        .withData(data)
        .build();

    // 将CloudEvent转换为Spring消息
    org.springframework.messaging.Message<CloudEvent> message = MessageBuilder.withPayload(cloudEvent)
        .setHeader(CloudEventMessageUtils.ATTRIBUTES_CONTENT_TYPE, EventFormatProvider.getInstance().resolveFormatForEvent(cloudEvent).getMediaType())
        .build();

    // 发送Spring消息到Kafka主题
    source.output().send(message);
  }
}

3. Create a MyEventDataPOJO class called to represent the event data:

public class MyEventData {
    
    
  private String message;

  public String getMessage() {
    
    
    return message;
  }

  public void setMessage(String message) {
    
    
    this.message = message;
  }
}

4. Create an MyEventHandlerevent target called , which listens to a Kafka topic and handles received events:

import org.springframework.cloud.stream.annotation.EnableBinding;
import org.springframework.cloud.stream.annotation.StreamListener;
import org.springframework.cloud.stream.messaging.Sink;
import org.springframework.stereotype.Component;
import io.cloudevents.CloudEvent;
import io.cloudevents.core.data.PojoCloudEventData;
import io.cloudevents.jackson.JsonCloudEventData;
import io.cloudevents.spring.messaging.CloudEventMessageUtils;

@Component
@EnableBinding(Sink.class)
public class MyEventHandler {
    
    
  @StreamListener(Sink.INPUT)
  public void handleEvent(CloudEvent cloudEvent) {
    
    
    // 从CloudEvent中获取事件数据
    MyEventData eventData = cloudEvent.getData() instanceof PojoCloudEventData ?
        ((PojoCloudEventData<MyEventData>) cloudEvent.getData()).get() :
        new JsonCloudEventData<>(cloudEvent.getData().toBytes(), MyEventData.class).get();

    // 处理事件
    System.out.println("Received event with message: " + eventData.getMessage());

    // 手动确认接收到事件
    CloudEventMessageUtils.confirm(cloudEvent);
  }
}

The above code uses @StreamListenerannotations to listen to events in the Kafka topic, and obtains event data from CloudEvent (here uses PojoCloudEventDatatwo JsonCloudEventDatamethods), then processes the event, and manually confirms the receipt of the event.

5. Finally, configure the Kafka topic and event serializer in the configuration file of the Spring Boot application:

spring:
  cloud:
    stream:
      bindings:
        output:
          destination: my-topic
          content-type: application/cloudevents+json
        input:
          destination: my-topic
          content-type: application/cloudevents+json
      kafka:
        binder:
          brokers: localhost:9092
      default:
        producer:
          useNativeEncoding: true
          headerMode: embeddedHeaders
          valueSerde: io.cloudevents.jackson.JsonCloudEventDataSerde

In the above configuration, outputand inputcorrespond to the Kafka topics of the event source and event target respectively. content-typeSet to application/cloudevents+json, which means to use the JSON format in the Cloud Events specification for event serialization. valueSerdeSet to JsonCloudEventDataSerde, for serializing event data into JSON format. useNativeEncodingand headerModesettings for enabling Cloud Events' native encoding and embedded header modes.

We have now created an example of Cloud Events integration using Spring Boot, which implements event sources and event destinations that can send events to and receive events from Kafka topics. You can modify the code and configuration according to your needs.