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。