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{
@Override
public 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;
}
@Override
public 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 {
@Autowired
SpringContextUtil 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。