spring boot 集成 cloud events

问：

用spring boot 集成 cloud events ,写一个实例，实现事件源和事件目标。

ChatGPT：

好的，下面是一个使用Spring Boot集成Cloud Events的示例，它实现了事件源和事件目标：

1.首先，需要添加以下Maven依赖项，以使用Spring Cloud Stream和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.然后，创建一个名为Source的事件源，用于将事件发送到Kafka主题：

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.创建一个名为MyEventData的POJO类，用于表示事件数据：

public class MyEventData {
    
    
  private String message;

  public String getMessage() {
    
    
    return message;
  }

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

4.创建一个名为MyEventHandler的事件目标，用于监听Kafka主题并处理接收到的事件：

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);
  }
}

上述代码使用了@StreamListener注解来监听Kafka主题中的事件，并从CloudEvent中获取事件数据（这里使用了PojoCloudEventData和JsonCloudEventData两种方式），然后处理事件，并手动确认接收到事件。

5.最后，在Spring Boot应用程序的配置文件中配置Kafka主题和事件序列化器：

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

上述配置中，output和input分别对应事件源和事件目标的Kafka主题。content-type设置为application/cloudevents+json，表示使用Cloud Events规范中的JSON格式进行事件序列化。valueSerde设置为JsonCloudEventDataSerde，用于将事件数据序列化为JSON格式。useNativeEncoding和headerMode设置用于启用Cloud Events的本地编码和嵌入式头部模式。

现在，我们已经创建了一个使用Spring Boot集成Cloud Events的示例，它实现了事件源和事件目标，可以将事件发送到Kafka主题并从中接收事件。你可以根据自己的需求修改代码和配置。