How to eliminate switch-case in Springboot

The basic logic is as follows:

 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:
    }

After writing, you will find that as the events increase, this code will be very long, and the processing functions of each event are also concentrated in one class. Easy to maintain. Therefore, through search and learning, we found that we can use Springboot's annotation, strategy mode, and simple factory to eliminate switch-case.

Refactoring

Define structure

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;
  }
}

Define an annotation

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface CRSEventAnnotation {

  CRSEvent value();
}

Definition Event processing interface

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

All time processing classes must implement this interface. Among them, execute is the event processing method

Write a specific time processing class

Next, write the event processing class one by one, give the following example:

@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;
  }
}

Define SpringContext tool class

@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;
  }
}

Define event processing class factory to produce various event processing objects

@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);
  }
}

Calling code modification

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

In this way, there is no switch-case in the code, and adding an event is also very simple. You only need to implement the EventProcess interface.

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