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

红太狼 2022-03-15 06:28 563阅读 0赞

## 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.cloud</groupId>
     	 	<artifactId>spring-cloud-starter-bus-amqp</artifactId>
    	</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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[https_blog.csdn.net_shang_xs_article_details_87911756]: https://blog.csdn.net/shang_xs/article/details/87911756
[https_blog.csdn.net_shang_xs_article_details_88048545]: https://blog.csdn.net/shang_xs/article/details/88048545
[https_blog.csdn.net_shang_xs_article_details_88050196]: https://blog.csdn.net/shang_xs/article/details/88050196
[https_blog.csdn.net_shang_xs_article_details_88051207]: https://blog.csdn.net/shang_xs/article/details/88051207