Spring Boot + Redis + 注解 + 拦截器来实现接口幂等性校验

喜欢ヅ旅行 2021-08-19 12:01 297阅读 0赞

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![format_png][]

作者 | wangzaiplus

链接 | www.jianshu.com/p/6189275403ed

## **一、概念** ##

幂等性, 通俗的说就是一个接口, 多次发起同一个请求, 必须保证操作只能执行一次  
比如:

*  订单接口, 不能多次创建订单
 *  支付接口, 重复支付同一笔订单只能扣一次钱
 *  支付宝回调接口, 可能会多次回调, 必须处理重复回调
 *  普通表单提交接口, 因为网络超时等原因多次点击提交, 只能成功一次  
    等等

## **二****、常见解决方案** ##

*  唯一索引 -- 防止新增脏数据
 *  token机制 -- 防止页面重复提交
 *  悲观锁 -- 获取数据的时候加锁(锁表或锁行)
 *  乐观锁 -- 基于版本号version实现, 在更新数据那一刻校验数据
 *  分布式锁 -- redis(jedis、redisson)或zookeeper实现
 *  状态机 -- 状态变更, 更新数据时判断状态

## **三、本文实现** ##

本文采用第2种方式实现, 即通过redis + token机制实现接口幂等性校验

## **四、实现思路** ##

为需要保证幂等性的每一次请求创建一个唯一标识token, 先获取token, 并将此token存入redis, 请求接口时, 将此token放到header或者作为请求参数请求接口, 后端接口判断redis中是否存在此token:

*  如果存在, 正常处理业务逻辑, 并从redis中删除此token, 那么, 如果是重复请求, 由于token已被删除, 则不能通过校验, 返回请勿重复操作提示
 *  如果不存在, 说明参数不合法或者是重复请求, 返回提示即可

## **五、项目简介** ##

*  springboot
 *  redis
 *  @ApiIdempotent注解 + 拦截器对请求进行拦截
 *  @ControllerAdvice全局异常处理
 *  压测工具: jmeter

**说明:**

本文重点介绍幂等性核心实现, 关于springboot如何集成redis、ServerResponse、ResponseCode等细枝末节不在本文讨论范围之内, 有兴趣的小伙伴可以查看我的Github项目:

> https://github.com/wangzaiplus/springboot/tree/wxw

## **六、代码实现** ##

**pom**

<dependency>
         <groupId>redis.clients</groupId>
         <artifactId>jedis</artifactId>
         <version>2.9.0</version>
    </dependency>
    
    
    <dependency>
       <groupId>org.projectlombok</groupId>
       <artifactId>lombok</artifactId>
       <version>1.16.10</version>
    </dependency>

**JedisUtil**

@Component
    @Slf4j
    public class JedisUtil {
    
        @Autowired
        private JedisPool jedisPool;
    
        private Jedis getJedis() {
            return jedisPool.getResource();
        }
    
        /**
         * 设值
         *
         * @param key
         * @param value
         * @return
         */
        public String set(String key, String value) {
            Jedis jedis = null;
            try {
                jedis = getJedis();
                return jedis.set(key, value);
            } catch (Exception e) {
                log.error("set key:{} value:{} error", key, value, e);
                return null;
            } finally {
                close(jedis);
            }
        }
    
        /**
         * 设值
         *
         * @param key
         * @param value
         * @param expireTime 过期时间, 单位: s
         * @return
         */
        public String set(String key, String value, int expireTime) {
            Jedis jedis = null;
            try {
                jedis = getJedis();
                return jedis.setex(key, expireTime, value);
            } catch (Exception e) {
                log.error("set key:{} value:{} expireTime:{} error", key, value, expireTime, e);
                return null;
            } finally {
                close(jedis);
            }
        }
    
        /**
         * 取值
         *
         * @param key
         * @return
         */
        public String get(String key) {
            Jedis jedis = null;
            try {
                jedis = getJedis();
                return jedis.get(key);
            } catch (Exception e) {
                log.error("get key:{} error", key, e);
                return null;
            } finally {
                close(jedis);
            }
        }
    
        /**
         * 删除key
         *
         * @param key
         * @return
         */
        public Long del(String key) {
            Jedis jedis = null;
            try {
                jedis = getJedis();
                return jedis.del(key.getBytes());
            } catch (Exception e) {
                log.error("del key:{} error", key, e);
                return null;
            } finally {
                close(jedis);
            }
        }
    
        /**
         * 判断key是否存在
         *
         * @param key
         * @return
         */
        public Boolean exists(String key) {
            Jedis jedis = null;
            try {
                jedis = getJedis();
                return jedis.exists(key.getBytes());
            } catch (Exception e) {
                log.error("exists key:{} error", key, e);
                return null;
            } finally {
                close(jedis);
            }
        }
    
        /**
         * 设值key过期时间
         *
         * @param key
         * @param expireTime 过期时间, 单位: s
         * @return
         */
        public Long expire(String key, int expireTime) {
            Jedis jedis = null;
            try {
                jedis = getJedis();
                return jedis.expire(key.getBytes(), expireTime);
            } catch (Exception e) {
                log.error("expire key:{} error", key, e);
                return null;
            } finally {
                close(jedis);
            }
        }
    
        /**
         * 获取剩余时间
         *
         * @param key
         * @return
         */
        public Long ttl(String key) {
            Jedis jedis = null;
            try {
                jedis = getJedis();
                return jedis.ttl(key);
            } catch (Exception e) {
                log.error("ttl key:{} error", key, e);
                return null;
            } finally {
                close(jedis);
            }
        }
    
        private void close(Jedis jedis) {
            if (null != jedis) {
                jedis.close();
            }
        }
    
    }

**自定义注解@ApiIdempotent**

/**
     * 在需要保证 接口幂等性 的Controller的方法上使用此注解
     */
    @Target({ElementType.METHOD})
    @Retention(RetentionPolicy.RUNTIME)
    public @interface ApiIdempotent {
    }

**ApiIdempotentInterceptor拦截器**

/**
     * 接口幂等性拦截器
     */
    public class ApiIdempotentInterceptor implements HandlerInterceptor {
    
        @Autowired
        private TokenService tokenService;
    
        @Override
        public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
            if (!(handler instanceof HandlerMethod)) {
                return true;
            }
    
            HandlerMethod handlerMethod = (HandlerMethod) handler;
            Method method = handlerMethod.getMethod();
    
            ApiIdempotent methodAnnotation = method.getAnnotation(ApiIdempotent.class);
            if (methodAnnotation != null) {
                check(request);// 幂等性校验, 校验通过则放行, 校验失败则抛出异常, 并通过统一异常处理返回友好提示
            }
    
            return true;
        }
    
        private void check(HttpServletRequest request) {
            tokenService.checkToken(request);
        }
    
        @Override
        public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {
        }
    
        @Override
        public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
        }
    }

**TokenServiceImpl**

@Service
    public class TokenServiceImpl implements TokenService {
    
        private static final String TOKEN_NAME = "token";
    
        @Autowired
        private JedisUtil jedisUtil;
    
        @Override
        public ServerResponse createToken() {
            String str = RandomUtil.UUID32();
            StrBuilder token = new StrBuilder();
            token.append(Constant.Redis.TOKEN_PREFIX).append(str);
    
            jedisUtil.set(token.toString(), token.toString(), Constant.Redis.EXPIRE_TIME_MINUTE);
    
            return ServerResponse.success(token.toString());
        }
    
        @Override
        public void checkToken(HttpServletRequest request) {
            String token = request.getHeader(TOKEN_NAME);
            if (StringUtils.isBlank(token)) {// header中不存在token
                token = request.getParameter(TOKEN_NAME);
                if (StringUtils.isBlank(token)) {// parameter中也不存在token
                    throw new ServiceException(ResponseCode.ILLEGAL_ARGUMENT.getMsg());
                }
            }
    
            if (!jedisUtil.exists(token)) {
                throw new ServiceException(ResponseCode.REPETITIVE_OPERATION.getMsg());
            }
    
            Long del = jedisUtil.del(token);
            if (del <= 0) {
                throw new ServiceException(ResponseCode.REPETITIVE_OPERATION.getMsg());
            }
        }
    
    }

**TestApplication**

@SpringBootApplication
    @MapperScan("com.wangzaiplus.test.mapper")
    public class TestApplication  extends WebMvcConfigurerAdapter {
    
        public static void main(String[] args) {
            SpringApplication.run(TestApplication.class, args);
        }
    
        /**
         * 跨域
         * @return
         */
        @Bean
        public CorsFilter corsFilter() {
            final UrlBasedCorsConfigurationSource urlBasedCorsConfigurationSource = new UrlBasedCorsConfigurationSource();
            final CorsConfiguration corsConfiguration = new CorsConfiguration();
            corsConfiguration.setAllowCredentials(true);
            corsConfiguration.addAllowedOrigin("*");
            corsConfiguration.addAllowedHeader("*");
            corsConfiguration.addAllowedMethod("*");
            urlBasedCorsConfigurationSource.registerCorsConfiguration("/**", corsConfiguration);
            return new CorsFilter(urlBasedCorsConfigurationSource);
        }
    
        @Override
        public void addInterceptors(InterceptorRegistry registry) {
            // 接口幂等性拦截器
            registry.addInterceptor(apiIdempotentInterceptor());
            super.addInterceptors(registry);
        }
    
        @Bean
        public ApiIdempotentInterceptor apiIdempotentInterceptor() {
            return new ApiIdempotentInterceptor();
        }
    
    }

OK, 目前为止, 校验代码准备就绪, 接下来测试验证

## **七、测试验证** ##

**1、获取token的控制器TokenController**

@RestController
    @RequestMapping("/token")
    public class TokenController {
    
        @Autowired
        private TokenService tokenService;
    
        @GetMapping
        public ServerResponse token() {
            return tokenService.createToken();
        }
    
    }

**2、TestController, 注意@ApiIdempotent注解, 在需要幂等性校验的方法上声明此注解即可, 不需要校验的无影响**

@RestController
    @RequestMapping("/test")
    @Slf4j
    public class TestController {
    
        @Autowired
        private TestService testService;
    
        @ApiIdempotent
        @PostMapping("testIdempotence")
        public ServerResponse testIdempotence() {
            return testService.testIdempotence();
        }
    
    }

**3、获取token**

**![format_png 1][]**

查看redis

![format_png 2][]

**4、测试接口安全性: 利用jmeter测试工具模拟50个并发请求, 将上一步获取到的token作为参数**

**![format_png 3][]**

**![format_png 4][]**

**5、header或参数均不传token, 或者token值为空, 或者token值乱填, 均无法通过校验, 如token值为"abcd"**

**![format_png 5][]**

## **八、注意点(非常重要)** ##

![format_png 6][]

上图中, 不能单纯的直接删除token而不校验是否删除成功, 会出现并发安全性问题, 因为, 有可能多个线程同时走到第46行, 此时token还未被删除, 所以继续往下执行, 如果不校验jedisUtil.del(token)的删除结果而直接放行, 那么还是会出现重复提交问题, 即使实际上只有一次真正的删除操作, 下面重现一下

稍微修改一下代码:

![format_png 7][]

再次请求

![format_png 8][]

再看看控制台

![format_png 9][]

虽然只有一个真正删除掉token, 但由于没有对删除结果进行校验, 所以还是有并发问题, 因此, 必须校验

## **九、总结** ##

其实思路很简单, 就是每次请求保证唯一性, 从而保证幂等性, 通过拦截器+注解, 就不用每次请求都写重复代码, 其实也可以利用spring aop实现， 无所谓。

Github

> https://github.com/wangzaiplus/springboot/tree/wxw

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