/**
 * 打折策略枚舉
 */
public enum ActivityStrategyEnum {
    MEMBER(1, "普通會(huì)員"),
    GOLD_MEMBER(2, "黃金會(huì)員"),
    DIAMOND_MEMBER(3, "鉆石會(huì)員"),
    ;
    private int code;
    private String name;
    ActivityStrategyEnum (int code, String name) {
        this.code = code;
        this.name = name;
    }
    /**
     * 通過(guò)code匹配對(duì)應(yīng)枚舉
     * @param code
     * @return
     */
    public static ActivityStrategyEnum match(int code){
        ActivityStrategyEnum strategyEnum = null;
        for (ActivityStrategyEnum item : values()){
            if(item.getCode() == code){
                strategyEnum = item;
                break;
            }
        }
        return strategyEnum;
    }
    public int getCode() {
        return code;
    }
    public String getName() {
        return name;
    }
}

//打折接口
public interface IActivityStrategyService {
    //策略code    
    int getCode();
	/**
	 * 打折
	 * @param money
	 * @return 應(yīng)付金額
	 */
	BigDecimal calculate(BigDecimal money);
}
@Service("memberService ")
public class MemberService implements IActivityStrategyService {
    @Override
    public int getCode() {
        return ActivityStrategyEnum.MEMBER.getCode();
    }
	@Override
	public BigDecimal calculate(BigDecimal money) {
		//普通會(huì)員9折
		return money.multiply(new BigDecimal(0.9)).setScale(2, RoundingMode.HALF_UP);
	}
}
@Service("goldMemberService")
public class GoldMemberService implements IActivityStrategyService {
    @Override
    public int getCode() {
        return ActivityStrategyEnum.GOLD_MEMBER.getCode();
    }
	@Override
	public BigDecimal calculate(BigDecimal money) {
		//黃金會(huì)員8折
		return money.multiply(new BigDecimal(0.8)).setScale(2, RoundingMode.HALF_UP);
	}
}
@Service("diamondMemberService")
public class DiamondMemberService implements IActivityStrategyService {
    @Override
    public int getCode() {
        return ActivityStrategyEnum.DIAMOND_MEMBER.getCode();
    }
	@Override
	public BigDecimal calculate(BigDecimal money) {
		//鉆石會(huì)員7折
		return money.multiply(new BigDecimal(0.7)).setScale(2, RoundingMode.HALF_UP);
	}
}

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
@Component
public class ActivityStrategyHandler implements InitializingBean, ApplicationContextAware {
    /**
     * 存放策略的map,可以理解為策略的注冊(cè)中心
     */
    private final Map<Integer, IActivityStrategyService> serviceHashMap = new ConcurrentHashMap<>();
    /**
     * spring的上下文
     */
    private ApplicationContext applicationContext;
    /**
     * 將StrategyService的類都按照定義好的規(guī)則（枚舉code），放入strategyServiceMap中
     *
     * @throws Exception
     */
    @Override
    public void afterPropertiesSet() throws Exception {
        Map<String, IActivityStrategyService> matchBeans = applicationContext.getBeansOfType(IActivityStrategyService.class);
        for (IActivityStrategyService strategyService : matchBeans.values()) {
            serviceHashMap.put(strategyService.getCode(), strategyService);
            System.out.println("初始化策略模式的鍵值對(duì) code =" + strategyService.getCode() + " ,value=" + strategyService);
        }
    }
    /**
     * 注入applicationContext
     *
     * @param applicationContext
     * @throws BeansException
     */
    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.applicationContext = applicationContext;
    }
    /**
     * 通過(guò)枚舉code獲取對(duì)應(yīng)對(duì)更新服務(wù)
     * @param strategyEnum
     * @return
     */
    public IActivityStrategyService getActivityService(ActivityStrategyEnum strategyEnum){
        return serviceHashMap.get(strategyEnum.getCode());
    }
}

@RestController
public class IndexController {
    @Autowired
    private ActivityStrategyHandler activityHandler;
    @GetMapping("/acitivity")
    public BigDecimal acitivity(int code) throws JsonProcessingException {
        //會(huì)員類型code
        ActivityStrategyEnum strategyEnum = ActivityStrategyEnum.match(code);
        IActivityStrategyService activityService = activityHandler.getActivityService(strategyEnum);
        //獲取商品金額
        BigDecimal amount = new BigDecimal(100);
        //調(diào)用具體的打折策略算法
        BigDecimal price = activityService.calculate(amount);
        return price ;
    }
}