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作者：wangzaiplus
鏈接：https://www.jianshu.com/p/6189275403ed
一、概念
冪等性, 通俗的說就是一個接口, 多次發(fā)起同一個請求, 必須保證操作只能執(zhí)行一次 比如:
訂單接口, 不能多次創(chuàng)建訂單
支付接口, 重復(fù)支付同一筆訂單只能扣一次錢
支付寶回調(diào)接口, 可能會多次回調(diào), 必須處理重復(fù)回調(diào)
普通表單提交接口, 因為網(wǎng)絡(luò)超時等原因多次點擊提交, 只能成功一次 等等
二、常見解決方案
唯一索引 -- 防止新增臟數(shù)據(jù)
token機制 -- 防止頁面重復(fù)提交
悲觀鎖 -- 獲取數(shù)據(jù)的時候加鎖(鎖表或鎖行)
樂觀鎖 -- 基于版本號version實現(xiàn), 在更新數(shù)據(jù)那一刻校驗數(shù)據(jù)
分布式鎖 -- redis(jedis、redisson)或zookeeper實現(xiàn)
狀態(tài)機 -- 狀態(tài)變更, 更新數(shù)據(jù)時判斷狀態(tài)
三、本文實現(xiàn)
本文采用第2種方式實現(xiàn), 即通過redis + token機制實現(xiàn)接口冪等性校驗
四、實現(xiàn)思路
為需要保證冪等性的每一次請求創(chuàng)建一個唯一標(biāo)識token, 先獲取token, 并將此token存入redis, 請求接口時, 將此token放到header或者作為請求參數(shù)請求接口, 后端接口判斷redis中是否存在此token:
如果存在, 正常處理業(yè)務(wù)邏輯, 并從redis中刪除此token, 那么, 如果是重復(fù)請求, 由于token已被刪除, 則不能通過校驗, 返回請勿重復(fù)操作提示
如果不存在, 說明參數(shù)不合法或者是重復(fù)請求, 返回提示即可
五、項目簡介
說明:
六、代碼實現(xiàn)
pom
<!-- Redis-Jedis --><dependency><groupId>redis.clients</groupId><artifactId>jedis</artifactId><version>2.9.0</version></dependency><!--lombok 本文用到@Slf4j注解, 也可不引用, 自定義log即可--><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><version>1.16.10</version></dependency>
JedisUtil
package com.wangzaiplus.test.util;import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;@Component
@Slf4j
public class JedisUtil {@Autowiredprivate JedisPool jedisPool;private Jedis getJedis() {return jedisPool.getResource();}/*** 設(shè)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(shè)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(shè)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);}}/*** 獲取剩余時間** @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();}}}
自定義注解@ApiIdempotent
package com.wangzaiplus.test.annotation;import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;/*** 在需要保證 接口冪等性 的Controller的方法上使用此注解*/
@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface ApiIdempotent {
}
ApiIdempotentInterceptor攔截器
package com.wangzaiplus.test.interceptor;import com.wangzaiplus.test.annotation.ApiIdempotent;
import com.wangzaiplus.test.service.TokenService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.lang.reflect.Method;/*** 接口冪等性攔截器*/
public class ApiIdempotentInterceptor implements HandlerInterceptor {@Autowiredprivate TokenService tokenService;@Overridepublic 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, 校驗失敗則拋出異常, 并通過統(tǒng)一異常處理返回友好提示}return true;}private void check(HttpServletRequest request) {tokenService.checkToken(request);}@Overridepublic void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {}@Overridepublic void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {}
}
TokenServiceImpl
package com.wangzaiplus.test.service.impl;import com.wangzaiplus.test.common.Constant;
import com.wangzaiplus.test.common.ResponseCode;
import com.wangzaiplus.test.common.ServerResponse;
import com.wangzaiplus.test.exception.ServiceException;
import com.wangzaiplus.test.service.TokenService;
import com.wangzaiplus.test.util.JedisUtil;
import com.wangzaiplus.test.util.RandomUtil;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang3.StringUtils;
import org.apache.commons.lang3.text.StrBuilder;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;import javax.servlet.http.HttpServletRequest;@Service
public class TokenServiceImpl implements TokenService {private static final String TOKEN_NAME = "token";@Autowiredprivate JedisUtil jedisUtil;@Overridepublic 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());}@Overridepublic void checkToken(HttpServletRequest request) {String token = request.getHeader(TOKEN_NAME);if (StringUtils.isBlank(token)) {// header中不存在tokentoken = request.getParameter(TOKEN_NAME);if (StringUtils.isBlank(token)) {// parameter中也不存在tokenthrow 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
package com.wangzaiplus.test;import com.wangzaiplus.test.interceptor.ApiIdempotentInterceptor;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.web.cors.CorsConfiguration;
import org.springframework.web.cors.UrlBasedCorsConfigurationSource;
import org.springframework.web.filter.CorsFilter;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;@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*/@Beanpublic 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);}@Overridepublic void addInterceptors(InterceptorRegistry registry) {// 接口冪等性攔截器registry.addInterceptor(apiIdempotentInterceptor());super.addInterceptors(registry);}@Beanpublic ApiIdempotentInterceptor apiIdempotentInterceptor() {return new ApiIdempotentInterceptor();}}
OK, 目前為止, 校驗代碼準(zhǔn)備就緒, 接下來測試驗證
七、測試驗證
獲取token的控制器TokenController
package com.wangzaiplus.test.controller;import com.wangzaiplus.test.common.ServerResponse;
import com.wangzaiplus.test.service.TokenService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;@RestController
@RequestMapping("/token")
public class TokenController {@Autowiredprivate TokenService tokenService;@GetMappingpublic ServerResponse token() {return tokenService.createToken();}}
TestController, 注意@ApiIdempotent注解, 在需要冪等性校驗的方法上聲明此注解即可, 不需要校驗的無影響
package com.wangzaiplus.test.controller;import com.wangzaiplus.test.annotation.ApiIdempotent;
import com.wangzaiplus.test.common.ServerResponse;
import com.wangzaiplus.test.service.TestService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;@RestController
@RequestMapping("/test")
@Slf4j
public class TestController {@Autowiredprivate TestService testService;@ApiIdempotent@PostMapping("testIdempotence")public ServerResponse testIdempotence() {return testService.testIdempotence();}}
獲取token
查看redis
測試接口安全性: 利用jmeter測試工具模擬50個并發(fā)請求, 將上一步獲取到的token作為參數(shù)
header或參數(shù)均不傳token, 或者token值為空, 或者token值亂填, 均無法通過校驗, 如token值為"abcd"
八、注意點(非常重要)
上圖中, 不能單純的直接刪除token而不校驗是否刪除成功, 會出現(xiàn)并發(fā)安全性問題, 因為, 有可能多個線程同時走到第46行, 此時token還未被刪除, 所以繼續(xù)往下執(zhí)行, 如果不校驗jedisUtil.del(token)的刪除結(jié)果而直接放行, 那么還是會出現(xiàn)重復(fù)提交問題, 即使實際上只有一次真正的刪除操作, 下面重現(xiàn)一下
稍微修改一下代碼:
再次請求
再看看控制臺
雖然只有一個真正刪除掉token, 但由于沒有對刪除結(jié)果進行校驗, 所以還是有并發(fā)問題, 因此, 必須校驗
九、總結(jié)
其實思路很簡單, 就是每次請求保證唯一性, 從而保證冪等性, 通過攔截器+注解, 就不用每次請求都寫重復(fù)代碼, 其實也可以利用spring aop實現(xiàn), 無所謂
如果小伙伴有什么疑問或者建議歡迎提出
Githubhttps://github.com/wangzaiplus/springboot/tree/wxw
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