发布ApplicationEventPublisher和监听ApplicationEvent事件的简单配置（注解实现）

悠悠 2021-09-07 10:50 358阅读 0赞

## 1.功能介绍 ##

通过事件的发布和监听联动，可以使核心业务与子业务进行解耦，也方便后期的业务的扩展。如新用户注册之后，需要发放优惠券，此时可以在保存用户之后，发布一个新用户的注册成功事件，通过监听该事件来实现发放优惠券的功能。后期新增一个对新用户进行xxx功能，此时可以新写一个监听注册成功事件的监听器，来处理新的业务逻辑，而不需要修改之前的注册逻辑。

## 2.主要依赖 ##

<parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.3.3.RELEASE</version>
            <relativePath/> 
        </parent>
    
     <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
            </dependency>
      <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
            </dependency>

## 3.代码实现 ##

事件类

@Data
    @AllArgsConstructor
    public class ReadNoteEvent { 
        private List<Long> noteIds;
        private String userId;
    }
    
    @Data
    @AllArgsConstructor
    public class SaveUserEvent{ 
        private List<Long> noteIds;
        private String userId;
    
    }

监听器  
@TransactionalEventListener(phase = TransactionPhase.AFTER\_COMMIT) 事务提交后再触发

@Component
    @AllArgsConstructor
    public class ReadNoteListener { 
    
        private final SysUserService sysUserService;
    
        @EventListener
        @Async
        public void readNoteListener(ReadNoteEvent event){ 
            System.out.println("1===="+sysUserService);
            System.out.println("1===="+event);
        }
    
        @TransactionalEventListener(phase = TransactionPhase.AFTER_COMMIT)
        public void saveNoteListener(SaveUserEvent event){ 
            System.out.println("2===="+sysUserService);
            System.out.println("2===="+event);
        }
    }
    
    @Component
    @AllArgsConstructor
    public class SaveUserListener { 
    
        private final SysUserService sysUserService;
    
        @Async
        @TransactionalEventListener(phase = TransactionPhase.AFTER_COMMIT)
        public void saveUserListener(SaveUserEvent saveUserEvent) { 
            System.out.println("3===="+sysUserService);
            System.out.println("3===="+saveUserEvent);
        }
    }

测试接口  
@Transactional(rollbackFor = Exception.class) 不能缺少，不然@TransactionalEventListener无法触发

@Autowired
        private ApplicationEventPublisher applicationContext;
    
     @Transactional(rollbackFor = Exception.class)
        @ApiOperation("订阅事件测试")
        @GetMapping(value = "/event")
        public ResultJson event(){ 
    
            List<Long> ids=new ArrayList<>();
            ids.add(1L);
            ids.add(2L);
            ids.add(3L);
            applicationContext.publishEvent(new ReadNoteEvent(ids,"11111111111"));
    
            SysUser user=new SysUser();
            user.setId(777L);
            user.setName("11114122");
            user.setAccount("3332333333333233");
            user.setPassword("44444");
            user.setStatus(0);
            user.setAvatar("222222222222222");
            userService.save(user);
            applicationContext.publishEvent(new SaveUserEvent(ids,"11111111111"));
            return ResultJson.ok();
        }

异步支持  
@Async 需要配置异步支持

@Configuration
    @EnableAsync
    public class AsyncConfig { 
    
        @Bean
        public ThreadPoolTaskExecutor taskExecutor() { 
            ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
            // 设置核心线程数，它是可以同时被执行的线程数量
            executor.setCorePoolSize(5);
            // 设置最大线程数,缓冲队列满了之后会申请超过核心线程数的线程
            executor.setMaxPoolSize(10);
            // 设置缓冲队列容量,
            executor.setQueueCapacity(20);
            // 设置线程生存时间（秒）,当超过了核心线程出之外的线程在生存时间到达之后会被销毁
            executor.setKeepAliveSeconds(60);
            // 设置线程名称前缀
            executor.setThreadNamePrefix("threadpool-");
            // 设置拒绝策略
            executor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
            // 等待所有任务结束后再关闭线程池
            executor.setWaitForTasksToCompleteOnShutdown(true);
            //初始化
            executor.initialize();
            return executor;
        }
    }