事件监听机制（四）Spring Cloud Bus自定义实现RemoteApplicationEvent

事件监听机制（四）Spring Cloud Bus自定义实现RemoteApplicationEvent

事件监听实现流程

1. 事件对象：
   继承自java.util.EventObject对象，由开发者自行定义实现。

2. 事件源：
   就是触发事件的源头，不同的事件源会触发不同的事件类型。

3. 事件监听器：
   事件监听器负责监听事件源发出的事件，事件监听器可以通过实现java.util.EventListener这个标识接口.，实现事件监听。

流程总结

事件源可以注册事件监听器对象，并可以向事件监听器对象发送事件对象，事件发生后，事件源将事件对象发给已经注册的所有事件监听器，监听器对象随后会根据事件对象内的相应方法响应这个事件。

相关依赖

 
	<dependency>
 		 <groupId>org.springframework.cloudgroupId>
 	 	<artifactId>spring-cloud-starter-bus-amqpartifactId>
	dependency>

自定义实现

添加自定义事件源pojo

/**
 * @ClassName: User 
 * @Description: 自定义事件源pojo
 * @Author: 尚先生
 * @CreateDate: 2019/3/1 10:08
 * @Version: 1.0
 */
public class User implements Serializable {

    private static final long serialVersionUID = -6789036732613612349L;

    /**
     * ID
     */
    private Long id;

    /**
     * 用户名
     */
    private String name;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                '}';
    }
}

添加自定义事件

/**
 * @ClassName: UserRemoteApplicationEvent 
 * @Description: 自定义事件
 * @Author: 尚先生
 * @CreateDate: 2019/3/1 10:10
 * @Version: 1.0
 */
public class UserRemoteApplicationEvent extends RemoteApplicationEvent {

    private UserRemoteApplicationEvent() {
    }

	//自定义User 
    public UserRemoteApplicationEvent(User user, String originService,
                                      String destinationService) {
        super(user, originService, destinationService);
    }

}

自定义@Configuration，添加 @RemoteApplicationEventScan

/**
 * @ClassName: BusConfiguration 
 * @Description: 自定义配置扫描类
 * @Author: 尚先生
 * @CreateDate: 2019/3/1 10:15
 * @Version: 1.0
 */
@Configuration
@RemoteApplicationEventScan(basePackageClasses = UserRemoteApplicationEvent.class)
public class BusConfiguration {
}

发布事件

/**
 * @ClassName: BusEventController 
 * @Description: 自定义发布事件
 * @Author: 尚先生
 * @CreateDate: 2019/3/1 10:23
 * @Version: 1.0
 */
@RestController
public class BusEventController implements ApplicationContextAware, ApplicationEventPublisherAware {

	// 时间发布器
    private ApplicationEventPublisher eventPublisher;

	//Spring上下文
    private ApplicationContext applicationContext;


	// 发布事件
    @PostMapping("/bus/event/publish/user")
    public boolean publishUserEvent(@RequestBody User user,
                                    @RequestParam(value = "destination", required = false) String destination) {

        String serviceInstanceId = applicationContext.getId();
        UserRemoteApplicationEvent event = new UserRemoteApplicationEvent(user, serviceInstanceId, destination);
        try {
       		 eventPublisher.publishEvent(event);
       	 	return true;   
       		 } catch (Exception e) {
        	return false;   
          	   }  
   		 }
    @Override
    public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) {
        this.eventPublisher = applicationEventPublisher;
    }
    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.applicationContext = applicationContext;
    }
}

自定义监听实现

 @EventListener
    public void onUserRemoteApplicationEvent(UserRemoteApplicationEvent event) {

        System.out.printf("UserRemoteApplicationEvent - " +
                        " Source : %s , originService : %s , destinationService : %s \n",
                event.getSource(),
                event.getOriginService(),
                event.getDestinationService());
    }

测试代码实现结果

http://localhost:8080/bus/event/publish/user?destination=user-service-client:8081

{
	"id":1,
	"name":"sxs"
}

测试结果

true

后续可扩展

1. 消息传递
   在下游对应监听中获取消息，进行后续相关处理
2. 消息存储
   如果消息是在内存或者是缓存中存储，后续可新增查询接口，进行消息存储结果查询

往期文章

博客地址：https://blog.csdn.net/shang_xs
微信公众号地址：http://mp.weixin.qq.com/mp/homepage?__biz=MzUxMzk4MDc1OQ==&hid=2&sn=c6c58c06f6f8403af27b6743648b3055&scene=18#wechat_redirect

完整代码及详情

具体依赖及相关源码参照

https://github.com/dwyanewede/segmentfault-lessons/tree/master/spring-cloud

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事件监听机制（三）Spring Cloud Bus流程分析
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