註解方式實現介面冪等性

阿新 • • 發佈：2020-08-28

一、概念

冪等性, 通俗的說就是一個介面, 多次發起同一個請求, 必須保證操作只能執行一次比如:

訂單介面, 不能多次建立訂單
支付介面, 重複支付同一筆訂單隻能扣一次錢
支付寶回撥介面, 可能會多次回撥, 必須處理重複回撥
普通表單提交介面, 因為網路超時等原因多次點選提交, 只能成功一次等等

二、常見解決方案

唯一索引 -- 防止新增髒資料
token機制 -- 防止頁面重複提交（本文實現方式）
悲觀鎖 -- 獲取資料的時候加鎖(鎖表或鎖行)
樂觀鎖 -- 基於版本號version實現, 在更新資料那一刻校驗資料
分散式鎖 -- redis(jedis、redisson)或zookeeper實現
狀態機 -- 狀態變更, 更新資料時判斷狀態

三、實現思路

為需要保證冪等性的每一次請求建立一個唯一標識token, 先獲取token, 並將此token存入redis, 請求介面時, 將此token放到header或者作為請求引數請求介面, 後端介面判斷redis中是否存在此token:

如果存在, 正常處理業務邏輯, 並從redis中刪除此token, 那麼, 如果是重複請求, 由於token已被刪除, 則不能通過校驗, 返回請勿重複操作提示
如果不存在, 說明引數不合法或者是重複請求, 返回提示即可

四、程式碼實現

JedisUtil

@Component
@Slf4j
 
public class JedisUtil {

    @Autowired
    private JedisPool jedisPool;

    private Jedis getJedis() {
        return jedisPool.getResource();
    }

    /**
     * 設值
     * @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);
        }
    }

    /**
     * 設值
     * @param key
     * @param value
     * @param expireTime 過期時間, 單位: 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);
        }
    }

    /**
     * 刪除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);
        }
    }

    /**
     * 判斷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);
        }
    }

    /**
     * 設值key過期時間
     * @param key
     * @param expireTime 過期時間, 單位: 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);
        }
    }

    /**
     * 獲取剩餘時間
     * @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();
        }
    }

}

自定義註解@ApiIdempotent

/**
 * 在需要保證 介面冪等性 的Controller的方法上使用此註解
 */
@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface ApiIdempotent {
}

ApiIdempotentInterceptor攔截器

/**
 * 介面冪等性攔截器
 */
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);// 冪等性校驗, 校驗通過則放行, 校驗失敗則丟擲異常, 並通過統一異常處理返回友好提示
        }

        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
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) {
        // 介面冪等性攔截器
        registry.addInterceptor(apiIdempotentInterceptor());
        super.addInterceptors(registry);
    }

    @Bean
    public ApiIdempotentInterceptor apiIdempotentInterceptor() {
        return new ApiIdempotentInterceptor();
    }
}

TestController, 注意@ApiIdempotent註解, 在需要冪等性校驗的方法上宣告此註解即可, 不需要校驗的無影響

@RestController
@RequestMapping("/test")
@Slf4j
public class TestController {

    @Autowired
    private TestService testService;

    @ApiIdempotent
    @PostMapping("testIdempotence")
    public ServerResponse testIdempotence() {
        return testService.testIdempotence();
    }

}