@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface TaskHandler {

  String taskType() default "";
}

public abstract class AbstractTaskHandler {

  /**
   * 任务执行器
   *
   * @param task 任务
   * @return 执行结果
   */
   public abstract BaseResult execute(Task task);
}

@TaskHandler(taskType = "UserNameChanged")
public class UserNameChangedSender extends AbstractTaskHandler {
  @Override
  public BaseResult execute(Task task) {
   return new BaseResult();
  }
}

public class TaskHandlerRegister extends ApplicationObjectSupport {

  private final static Map<String, AbstractTaskHandler> TASK_HANDLERS_MAP = new HashMap<>();

  private static final Logger LOGGER = LoggerFactory.getLogger(TaskHandlerRegister.class);

  @Override
  protected void initApplicationContext(ApplicationContext context) throws BeansException {
    super.initApplicationContext(context);
    Map<String, Object> taskBeanMap = context.getBeansWithAnnotation(TaskHandler.class);
    taskBeanMap.keySet().forEach(beanName -> {
      Object bean = taskBeanMap.get(beanName);
      Class clazz = bean.getClass();
      if (bean instanceof AbstractTaskHandler && clazz.getAnnotation(TaskHandler.class) != null) {
        TaskHandler taskHandler = (TaskHandler) clazz.getAnnotation(TaskHandler.class);
        String taskType = taskHandler.taskType();
        if (TASK_HANDLERS_MAP.keySet().contains(taskType)) {
          throw new RuntimeException("TaskType has Exits. TaskType=" + taskType);
        }
        TASK_HANDLERS_MAP.put(taskHandler.taskType(), (AbstractTaskHandler) taskBeanMap.get(beanName));
        LOGGER.info("Task Handler Register. taskType={},beanName={}", taskHandler.taskType(), beanName);
      }
    });
  }

  public static AbstractTaskHandler getTaskHandler(String taskType) {
    return TASK_HANDLERS_MAP.get(taskType);
  }
}

public class TaskExecutor implements Job {

  private static final String TASK_TYPE = "taskType";

  @Override
  public BaseResult execute(Task task){
    String taskType=task.getTaskType();
    if (TaskHandlerRegister.getTaskHandler(taskType) == null) {
      throw new RuntimeException("can't find taskHandler,taskType=" + taskType);
    }
    AbstractTaskHandler abstractHandler = TaskHandlerRegister.getTaskHandler(taskType);
    return abstractHandler.execute(task);
  }
}