@RestController
@RequestMapping("/api/order")
public class OrderTokenController {

    @Autowired
    private RedisTemplate<String, String> redisTemplate;

    @GetMapping("/token")
    public ResponseEntity<String> getToken() {
        String token = UUID.randomUUID().toString();
        String key = "order:token:" + token;

        // 設(shè)置有效期5分鐘
        redisTemplate.opsForValue().set(key, "valid", Duration.ofMinutes(5));

        return ResponseEntity.ok(token);
    }
}

@RestController
@RequestMapping("/api/order")
public class OrderController {

    @Autowired
    private OrderService orderService;

    @PostMapping("/submit")
    public ResponseEntity<String> submitOrder(@RequestBody OrderRequest request,
                                              @RequestHeader("X-Order-Token") String token) {
        boolean success = orderService.submitOrder(request, token);
        if (success) {
            return ResponseEntity.ok("訂單提交成功");
        } else {
            return ResponseEntity.status(HttpStatus.BAD_REQUEST).body("請(qǐng)勿重復(fù)提交訂單");
        }
    }
}

@Service
public class OrderService {

    @Autowired
    private RedisTemplate<String, String> redisTemplate;

    /**
     * 提交訂單接口，防止重復(fù)提交
     */
    public boolean submitOrder(OrderRequest request, String token) {
        String redisKey = "order:token:" + token;

        // 利用 Redis 的 delete + check 保證冪等性（原子性）
        Boolean result = redisTemplate.delete(redisKey);

        if (Boolean.TRUE.equals(result)) {
            // token存在并刪除 → 第一次提交
            // 執(zhí)行正常訂單創(chuàng)建邏輯
            createOrder(request);
            return true;
        } else {
            // token 不存在 → 重復(fù)提交
            return false;
        }
    }

    private void createOrder(OrderRequest request) {
        // 實(shí)際業(yè)務(wù)處理：生成訂單號(hào)、校驗(yàn)庫存、扣減庫存、寫庫、發(fā)MQ等
        System.out.println("處理訂單：" + request);
    }
}

@Data
public class OrderRequest {
    private Long userId;
    private List<Long> productIds;
    private BigDecimal totalAmount;
}

// Lua 腳本實(shí)現(xiàn)原子刪除
String script = "if redis.call('get', KEYS[1]) == ARGV[1] then " +
                "return redis.call('del', KEYS[1]) else return 0 end";

DefaultRedisScript<Long> redisScript = new DefaultRedisScript<>();
redisScript.setScriptText(script);
redisScript.setResultType(Long.class);

Long result = redisTemplate.execute(redisScript, Collections.singletonList(key), "valid");