public interface SeckillService {

    /**
     * 获取所有的秒杀商品列表
     *
     * @return
     */
    List<Seckill> findAll();

    /**
     * 获取某一条商品秒杀信息
     *
     * @param seckillId
     * @return
     */
    Seckill findById(long seckillId);

    /**
     * 秒杀开始时输出暴露秒杀的地址
     * 否者输出系统时间和秒杀时间
     *
     * @param seckillId
     */
    Exposer exportSeckillUrl(long seckillId);

    /**
     * 执行秒杀的操作
     *
     * @param seckillId
     * @param userPhone
     * @param money
     * @param md5
     */
    SeckillExecution executeSeckill(long seckillId, BigDecimal money, long userPhone, String md5)
            throws SeckillException, RepeatKillException, SeckillCloseException;
}

public class Exposer {

    //是否开启秒杀
    private boolean exposed;

    //加密措施，避免用户通过抓包拿到秒杀地址
    private String md5;

    //ID
    private long seckillId;

    //系统当前时间（毫秒）
    private long now;

    //秒杀开启时间
    private long start;

    //秒杀结束时间
    private long end;

    public Exposer(boolean exposed, String md5, long seckillId) {
        this.exposed = exposed;
        this.md5 = md5;
        this.seckillId = seckillId;
    }

    public Exposer(boolean exposed, Long seckillId, long now, long start, long end) {
        this.exposed = exposed;
        this.seckillId = seckillId;
        this.now = now;
        this.start = start;
        this.end = end;
    }

    public Exposer(boolean exposed, long seckillId) {
        this.exposed = exposed;
        this.seckillId = seckillId;
    }
}

SeckillExecution executeSeckill(long seckillId, BigDecimal money, long userPhone, String md5)
        throws SeckillException, RepeatKillException, SeckillCloseException;

public class SeckillExecution {

    private Long seckillId;

    //秒杀执行结果状态
    private int state;

    //状态表示
    private String stateInfo;

    //秒杀成功的订单对象
    private SeckillOrder seckillOrder;

    public SeckillExecution(Long seckillId, int state, String stateInfo, SeckillOrder seckillOrder) {
        this.seckillId = seckillId;
        this.state = state;
        this.stateInfo = stateInfo;
        this.seckillOrder = seckillOrder;
    }

    public SeckillExecution(Long seckillId, int state, String stateInfo) {
        this.seckillId = seckillId;
        this.state = state;
        this.stateInfo = stateInfo;
    }
}

public class SeckillCloseException extends SeckillException {

    public SeckillCloseException(String message) {
        super(message);
    }

    public SeckillCloseException(String message, Throwable cause) {
        super(message, cause);
    }
}

public class RepeatKillException extends SeckillException {

    public RepeatKillException(String message) {
        super(message);
    }

    public RepeatKillException(String message, Throwable cause) {
        super(message, cause);
    }
}

public class SeckillException extends RuntimeException {

    public SeckillException(String message) {
        super(message);
    }

    public SeckillException(String message, Throwable cause) {
        super(message, cause);
    }
}

@Service
public class SeckillServiceImpl implements SeckillService {
    private Logger logger = LoggerFactory.getLogger(this.getClass());

    //设置盐值字符串，随便定义，用于混淆MD5值
    private final String salt = "sjajaspu-i-2jrfm;sd";
    @Autowired
    private SeckillMapper seckillMapper;

    @Autowired
    private SeckillOrderMapper seckillOrderMapper;

    @Override
    public Exposer exportSeckillUrl(long seckillId) {
        Seckill seckill = seckillMapper.findById(seckillId);
        if (seckill == null) {
            //说明没有查询到
            return new Exposer(false, seckillId);
        }
        Date startTime = seckill.getStartTime();
        Date endTime = seckill.getEndTime();
        //获取系统时间
        Date nowTime = new Date();
        if (nowTime.getTime() < startTime.getTime() || nowTime.getTime() > endTime.getTime()) {
            return new Exposer(false, seckillId, nowTime.getTime(), startTime.getTime(), endTime.getTime());
        }
        //转换特定字符串的过程，不可逆的算法
        String md5 = getMD5(seckillId);
        return new Exposer(true, md5, seckillId);
    }

    //生成MD5值
    private String getMD5(Long seckillId) {
        String base = seckillId + "/" + salt;
        String md5 = DigestUtils.md5DigestAsHex(base.getBytes());
        return md5;
    }

@Override
@Transactional
public SeckillExecution executeSeckill(long seckillId, BigDecimal money, long userPhone, String md5)
        throws SeckillException, RepeatKillException, SeckillCloseException {
    if (md5 == null || !md5.equals(getMD5(seckillId))) {
        throw new SeckillException("seckill data rewrite");
    }
    //执行秒杀逻辑：1.减库存；2.储存秒杀订单
    Date nowTime = new Date();

    try {
        //记录秒杀订单信息
        int insertCount = seckillOrderMapper.insertOrder(seckillId, money, userPhone);
        //唯一性：seckillId,userPhone，保证一个用户只能秒杀一件商品
        if (insertCount <= 0) {
            //重复秒杀
            throw new RepeatKillException("seckill repeated");
        } else {
            //减库存
            int updateCount = seckillMapper.reduceStock(seckillId, nowTime);
            if (updateCount <= 0) {
                //没有更新记录，秒杀结束
                throw new SeckillCloseException("seckill is closed");
            } else {
                //秒杀成功
                SeckillOrder seckillOrder = seckillOrderMapper.findById(seckillId);
                return new SeckillExecution(seckillId, SeckillStatEnum.SUCCESS, seckillOrder);
            }
        }
    } catch (SeckillCloseException e) {
        throw e;
    } catch (RepeatKillException e) {
        throw e;
    } catch (Exception e) {
        logger.error(e.getMessage(), e);
        //所有编译期异常，转换为运行期异常
        throw new SeckillException("seckill inner error:" + e.getMessage());
    }
}

public enum SeckillStatEnum {
    SUCCESS(1, "秒杀成功"),
    END(0, "秒杀结束"),
    REPEAT_KILL(-1,"重复秒杀"),
    INNER_ERROR(-2, "系统异常"),
    DATA_REWRITE(-3, "数据串改");

    private int state;
    private String stateInfo;

    SeckillStatEnum(int state, String stateInfo) {
        this.state = state;
        this.stateInfo = stateInfo;
    }

    public int getState() {
        return state;
    }

    public String getStateInfo() {
        return stateInfo;
    }

    public static SeckillStatEnum stateOf(int index){
        for (SeckillStatEnum state : values()){
            if (state.getState() == index){
                return state;
            }
        }
        return null;
    }
}