if-else的另一种实现
背景
在日常开发中，经常会需要监听某种数据的新增、删除、修改。根据不同类型做处理，通常处理：
public interface MqService {
/**
* 处理mq消息
*
* @param mqMessageDTO
* @return
*/
Boolean handlerMsg(MQMessageDTO mqMessageDTO);
}
@Service
@Slf4j
public class MqServiceImpl implements MqService {
@Override
public Boolean handlerMsg(MQMessageDTO mqMessageDTO) {
try {
if (MQMessageDTO.MsgType.INSERT == mqMessageDTO.getMsgType()) {
// 处理新增数据
} else if (MQMessageDTO.MsgType.UPDATE == mqMessageDTO.getMsgType()) {
//处理修改数据
} else if (MQMessageDTO.MsgType.DELETE == mqMessageDTO.getMsgType()) {
//处理删除数据
}
return true;
} catch (Exception e) {
log.error("消息消费失败:{}", mqMessageDTO);
e.printStackTrace();
return false;
}
}
}这样如果类型较多会有大量if-else分支逻辑，我们可以换一种模式实现
定义三个不同类型的Handler
@Component
@HandlerAnnotation(MQMessageDTO.MsgType.DELETE)
public class DeleteHandler extends AbstractHandler {
@Override
public void handler() {
System.out.println("收到删除消息");
}
}
@Component
@HandlerAnnotation(MQMessageDTO.MsgType.INSERT)
public class InsertHandler extends AbstractHandler {
@Override
public void handler() {
System.out.println("收到新增消息");
}
}
@Component
@HandlerAnnotation(MQMessageDTO.MsgType.UPDATE)
public class UpdateHandler extends AbstractHandler {
@Override
public void handler() {
System.out.println("收到更新消息");
}
}定义一个注解,根据注解来调用哪个handler处理
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface HandlerAnnotation {
MQMessageDTO.MsgType value();
}工厂初始化的时候，注册HandlerContext
@Data
public class HandlerContext {
private Map<String, Object> handlerMap;
public HandlerContext(Map<String, Object> handlerMap) {
this.handlerMap = handlerMap;
}
}
@Component
public class HandlerProcessor implements BeanFactoryPostProcessor {
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException {
Map<String, Object> beansWithAnnotation = configurableListableBeanFactory.getBeansWithAnnotation(HandlerAnnotation.class);
Map<String, Object> typeHandler = Maps.newHashMap();
beansWithAnnotation.keySet().forEach(beanName -> {
MQMessageDTO.MsgType value = beansWithAnnotation.get(beanName).getClass().getAnnotation(HandlerAnnotation.class).value();
typeHandler.put(value.name(),beansWithAnnotation.get(beanName));
});
HandlerContext handlerContext = new HandlerContext(typeHandler);
configurableListableBeanFactory.registerResolvableDependency(HandlerContext.class, handlerContext);
}
}替换过的实现
@Service
@Slf4j
public class MqServiceImpl implements MqService {
@Autowired
private HandlerContext handlerContext;
@Override
public Boolean handlerMsg(MQMessageDTO mqMessageDTO) {
try {
/*if (MQMessageDTO.MsgType.INSERT == mqMessageDTO.getMsgType()) {
// 处理新增数据
} else if (MQMessageDTO.MsgType.UPDATE == mqMessageDTO.getMsgType()) {
//处理修改数据
} else if (MQMessageDTO.MsgType.DELETE == mqMessageDTO.getMsgType()) {
//处理删除数据
}*/
Map<String, Object> handlerMap = handlerContext.getHandlerMap();
AbstractHandler handler = (AbstractHandler)handlerMap.get(mqMessageDTO.getMsgType().name());
handler.handler();
return true;
} catch (Exception e) {
log.error("消息消费失败:{}", mqMessageDTO);
e.printStackTrace();
return false;
}
}
}本文参与 腾讯云自媒体分享计划，分享自作者个人站点/博客。
原始发表：2019.09.24 ，如有侵权请联系 cloudcommunity@tencent.com 删除
评论
登录后参与评论
推荐阅读
目录