[Spring]Spring的事件机制实践

/**
 * @Author JiaQIng
 * @Description 修改密码事件
 * @ClassName UserChangePasswordEvent
 * @Date 2023/3/26 13:55
 **/
@Getter
@Setter
public class UserChangePasswordEvent extends ApplicationEvent {
    private String userId;

    public UserChangePasswordEvent(String userId) {
        super(new Object());
        this.userId = userId;
    }
}

/**
 * @Author JiaQIng
 * @Description 发送短信监听器
 * @ClassName MessageListener
 * @Date 2023/3/26 14:16
 **/
@Component
public class MessageListener implements ApplicationListener<UserChangePasswordEvent> {

    @Override
    public void onApplicationEvent(UserChangePasswordEvent event) {
        System.out.println("收到事件:" + event);
        System.out.println("开始执行业务操作给用户发送短信。用户userId为：" + event.getUserId());
    }
}

/**
 * @Author JiaQIng
 * @Description 事件监听器
 * @ClassName LogListener
 * @Date 2023/3/26 14:22
 **/
@Component
public class ListenerEvent {

    @EventListener({ UserChangePasswordEvent.class })
    public void LogListener(UserChangePasswordEvent event) {
        System.out.println("收到事件:" + event);
        System.out.println("开始执行业务操作生成关键日志。用户userId为：" + event.getUserId());
    }

    @EventListener({ UserChangePasswordEvent.class })
    public void messageListener(UserChangePasswordEvent event) {
        System.out.println("收到事件:" + event);
        System.out.println("开始执行业务操作给用户发送短信。用户userId为：" + event.getUserId());
    }
}

// 在这个注解上面有一个注解：`@EventListener`，所以表明其实这个注解也是个事件监听器。 
@Target({ElementType.METHOD, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@EventListener
public @interface TransactionalEventListener {

	/**
	 * 这个注解取值有：BEFORE_COMMIT(指定目标方法在事务commit之前执行)、AFTER_COMMIT(指定目标方法在事务commit之后执行)、
	 *	AFTER_ROLLBACK(指定目标方法在事务rollback之后执行)、AFTER_COMPLETION(指定目标方法在事务完成时执行，这里的完成是指无论事务是成功提交还是事务回滚了)
	 * 各个值都代表什么意思表达什么功能，非常清晰，
	 * 需要注意的是：AFTER_COMMIT + AFTER_COMPLETION是可以同时生效的
	 * AFTER_ROLLBACK + AFTER_COMPLETION是可以同时生效的
	 */
	TransactionPhase phase() default TransactionPhase.AFTER_COMMIT;

	/**
	 * 表明若没有事务的时候，对应的event是否需要执行，默认值为false表示，没事务就不执行了。
	 */
	boolean fallbackExecution() default false;

	/**
	 *  这里巧妙的用到了@AliasFor的能力，放到了@EventListener身上
	 *  注意：一般建议都需要指定此值，否则默认可以处理所有类型的事件，范围太广了。
	 */
	@AliasFor(annotation = EventListener.class, attribute = "classes")
	Class<?>[] value() default {};

	/**
	 * The event classes that this listener handles.
	 * <p>If this attribute is specified with a single value, the annotated
	 * method may optionally accept a single parameter. However, if this
	 * attribute is specified with multiple values, the annotated method
	 * must <em>not</em> declare any parameters.
	 */
	@AliasFor(annotation = EventListener.class, attribute = "classes")
	Class<?>[] classes() default {};

	/**
	 * Spring Expression Language (SpEL) attribute used for making the event
	 * handling conditional.
	 * <p>The default is {@code ""}, meaning the event is always handled.
	 * @see EventListener#condition
	 */
	@AliasFor(annotation = EventListener.class, attribute = "condition")
	String condition() default "";

	/**
	 * An optional identifier for the listener, defaulting to the fully-qualified
	 * signature of the declaring method (e.g. "mypackage.MyClass.myMethod()").
	 * @since 5.3
	 * @see EventListener#id
	 * @see TransactionalApplicationListener#getListenerId()
	 */
	@AliasFor(annotation = EventListener.class, attribute = "id")
	String id() default "";

}

/**
 * @Author JiaQIng
 * @Description 事件监听器
 * @ClassName LogListener
 * @Date 2023/3/26 14:22
 **/
@Component
public class ListenerEvent {

    @EventListener({ UserChangePasswordEvent.class })
    public void logListener(UserChangePasswordEvent event) {
        System.out.println("收到事件:" + event);
        System.out.println("开始执行业务操作生成关键日志。用户userId为：" + event.getUserId());
    }

    @TransactionalEventListener(phase = TransactionPhase.AFTER_COMMIT,value = { UserChangePasswordEvent.class })
    public void messageListener(UserChangePasswordEvent event) {
        System.out.println("收到事件:" + event);
        System.out.println("开始执行业务操作给用户发送短信。用户userId为：" + event.getUserId());
    }
}

@SpringBootTest
class SpirngEventApplicationTests {
    @Autowired
    ApplicationEventPublisher appEventPublisher;
    @Test
    void contextLoads() {
        appEventPublisher.publishEvent(new UserChangePasswordEvent("1111111"));
    }

}

@EnableAsync
@SpringBootApplication
public class SpirngEventApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpirngEventApplication.class, args);
    }

}
复制代码

/**
 * @Author JiaQIng
 * @Description 事件监听器
 * @ClassName LogListener
 * @Date 2023/3/26 14:22
 **/
@Component
public class ListenerEvent {
    
    @Async
    @EventListener({ UserChangePasswordEvent.class })
    public void logListener(UserChangePasswordEvent event) {
        System.out.println("收到事件:" + event);
        System.out.println("开始执行业务操作生成关键日志。用户userId为：" + event.getUserId());
    }
}
复制代码