Springboot消除switch-case方法

背景
最近，在使用springboot开发一个接口的时候，需要根据接收的请求事件类型，去执行不同的操作，返回不同的结果，基本逻辑如下：

  String event = crsRequest.getEvent();CRSResponse crsResponse = null;switch (event) {case CRSRequestEvent.APP_START:crsResponse = processAppStartCommand(crsRequest);break;case CRSRequestEvent.INIT_COMPLETE:crsResponse = processInitCompleteCommand(crsRequest);break;case CRSRequestEvent.COLLECT_COMPLETE:crsResponse = processCollectCompleteCommand(crsRequest);break;case CRSRequestEvent.COLLECT_NO_INPUT:crsResponse = processCollectNoInputCommand(crsRequest);break;case CRSRequestEvent.PLAY_COMPLETE:crsResponse = processPlayCompleteCommand(crsRequest);break;default:}

写完会发现，随着事件的增加，这段代码会很长，每个事件的处理函数也都集中在一个类当中，不好维护。因此，通过搜索学习发现，可以使用Springboot的注解+策略模式+简单工厂的方式来消除switch-case。

重构

• 定义结构体

public enum CRSEvent {APP_START("APP_START"),INIT_COMPLETE("INIT_COMPLETE"),PLAY_COMPLETE("PLAY_COMPLETE"),COLLECT_COMPLETE("COLLECT_COMPLETE"),COLLECT_NO_INPUT("COLLECT_NO_INPUT"),APP_END("APP_END"),RESP_ERROR_CMD("RESP_ERROR_CMD");private String event;CRSEvent(String event){this.event = event;}public String getEvent() {return event;}public void setEvent(String event) {this.event = event;}
}

• 定义一个注解

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface CRSEventAnnotation {CRSEvent value();
}

• 定义事件处理接口

public interface EventProcess {CRSResponse execute(CRSRequest resquest);
}

所有的时间处理类都要实现这个接口。其中，execute是事件的处理方法

编写具体的时间处理类

接下来，逐个的编写事件处理类，举下面一个例子：

@Component("appStartProcess")
@CRSEventAnnotation(value = CRSEvent.APP_START)
public class AppStartProcess implements EventProcess{@Overridepublic CRSResponse execute(CRSRequest resquest) {CRSResponse response = new CRSResponse();response.setCommand(CRSResponseCmd.IVR_SESSION_INIT);CRSResponse.Message message = new CRSResponse.Message();message.setTts_vid("65580");message.setTts_speed("120");response.setMessage(message);return response;}
}

• 定义SpringContext工具类

@Component
public class SpringContextUtil implements ApplicationContextAware{private ApplicationContext context;public ApplicationContext getContext(){return context;}@Overridepublic void setApplicationContext(ApplicationContext applicationContext) throws BeansException {this.context = applicationContext;}
}

• 定义事件处理类工厂，用来生产各种事件处理对象

@Component
public class EventProcessFactory {@AutowiredSpringContextUtil contextUtil;private static Map<CRSEvent, EventProcess> eventProcessMap = new ConcurrentHashMap<>();public EventProcessFactory() {Map<String, Object> beanMap = contextUtil.getContext().getBeansWithAnnotation(CRSEventAnnotation.class);for (Object evetProcess : beanMap.values()) {CRSEventAnnotation annotation = evetProcess.getClass().getAnnotation(CRSEventAnnotation.class);eventProcessMap.put(annotation.value(), (EventProcess) evetProcess);}}public static EventProcess createEventProcess(CRSEvent event){return eventProcessMap.get(event);}
}

• 调用代码修改

 CRSEvent crsEvent = CRSEvent.valueOf(crsRequest.getEvent());EventProcess eventProcess = EventProcessFactory.createEventProcess(crsEvent);if (eventProcess != null){return eventProcess.execute(crsRequest);}
return null;

这样，代码就没有了switch-case，增加一个事件也很简单，只需要实现EventProcess接口即可。

原博客