策略模式优化if...else

场景

根据第三方系统的事件做出不同动作

优化前

@Slf4j
@RestController
@RequiredArgsConstructor
public class WebHookController {

    @PostMapping("/webhook")
    public ResponseEntity<Object> webhook(@RequestBody JSONObject body) {
		String event = body.getString("event");
		
		if(event == "***"){
			log.info("==>***事件")
			// do
		}else if(event == "***"){
			log.info("==>***事件")
			// do
		}else if(event == "***"){
			log.info("==>***事件")
			// do
		}else if(event == "***"){
			log.info("==>***事件")
			// do
		}else if(event == "***"){
			log.info("==>***事件")
			// do
		}else if(event == "***"){
			log.info("==>***事件")
			// do
		}else if(event == "***"){
			log.info("==>***事件")
			// do
		}

        return ResponseEntity.ok().build();
	}
}

事件枚举

public enum EventType {
    PROJECT_CREATE,
	TASK_CREATE,
	WORKTIME_CREATE
}

事件处理接口

public interface IEventTemplate{
	void process(JSONObject json)
}

抽象模板

public abstract class AbstractEventTemplate implements IEventTemplate,InitializingBean{

	public abstract EventType support();

	@Override
	public void afterPropertiesSet() throws Exception{
		EventType[] eventTypes = EventType.values();

		boolean flag = false;
		for(EventType eventType : eventTypes){
			// support方法调用的是子类返回的对象
			EvenType support = support();
			if(support == eventType){
				flag = true;
				break;
			}
		}
	}

	if(!flag){
		throw new RuntimeException("不支持的事件类型");
	}
}

模板实现类

@Component
@Slf4j
public class ProjectCreateTemplate extends AbstractEventTemplate{
	@Override
	public void process(JSONObject json){
		log.info("==> 项目创建")
		// do
	}

	@Override
    public TBEventType support() {
        return EventType.PROJECT_CREATE;
    }
}

上下文

@Component
public class EventContext implements ApplicationContextAware{
	
	private final static Map<EventType,IEventTemplate> eventService = new EnumMap<>(EventType.class);
	
	@Override
	public void setApplicationContext(ApplicationContext applicationContext) throws BeanException{
		// 抽象类所有的子类对象 从容器中获取的所有子类对象
		Map<String, AbstractEventTemplate> beansOfType = applicationContext.getBeansOfType(AbstractEventTemplate.class); // 从容器中获取所有的子类对象 key=beanName     value=bean对象

		//循环抽象类的子类
        for (AbstractTBEventTemplate value : beansOfType.values()) {
            EventType support = value.support();
            eventServices.put(support, value);
        }
    }
	

    public IEventTemplate getEventService(TBEventType eventType) {
        return eventServices.get(eventType);
    }	
}

优化后接口

@Slf4j
@RestController
@RequiredArgsConstructor
public class WebHookController {

    @PostMapping("/webhook")
    public ResponseEntity<Object> webhook(@RequestBody JSONObject body) {
		String event = body.getString("event");
		try{
			EventType eventType = EventType.valueOf(event);
	        IEventTemplate eventTemplate = tbEventContext.getEventService(eventType);
	        eventTemplate.process(body);
		}catch (IllegalArgumentException illegalArgumentException) {
            log.info("未知事件：{}", body);
        } catch (Exception e) {
            log.error(e.getMessage());
            throw new RuntimeException(e);
       }

       return ResponseEntity.ok().build();
	}
}