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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, 重復支付同一筆訂單只能扣一次錢
支付寶回調接口, 可能會多次回調, 必須處理重復回調
普通表單提交接口, 因為網絡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 -- 防止新增臟數據
token機制 -- 防止頁面重復提交
悲觀鎖 -- 獲取數據的時候加鎖(鎖表或鎖行)
樂觀鎖 -- 基于版本號version實現, 在更新數據那一刻校驗數據
分布式鎖 -- redis(jedis、redisson)或zookeeper實現
狀態(tài)機 -- 狀態(tài)變更, 更新數據時判斷狀態(tài)

三、本文實現

本文采用第2種方式實現, 即通過redis + token機制實現接口冪等性校驗

四、實現思路

為需要保證冪等性的每一次請求創(chuàng)建一個唯一標識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)務邏輯, 并從redis中刪除此token, 那么, 如果是重復請求, 由于token已被刪除, 則不能通過校驗, 返回請勿重復操作提示
如果不存在, 說明參數不合法或者是重復請求, 返回提示即可

五、項目簡介

springboot
redis
@ApiIdempotent注解 + 攔截器對請求進行攔截
@ControllerAdvice全局異常處理
壓測工具: jmeter

說明:

本文重點介紹冪等性核心實現, 關于springboot如何集成redis、ServerResponse、ResponseCode等細枝末節(jié)不在本文討論范圍之內, 有興趣的小伙伴可以查看我的Github項目:

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

六、代碼實現

pom

????????
????????<dependency>
????????????<groupId>redis.clientsgroupId>
????????????<artifactId>jedisartifactId>
????????????<version>2.9.0version>
????????dependency>

????????
????????<dependency>
????????????<groupId>org.projectlombokgroupId>
????????????<artifactId>lombokartifactId>
????????????<version>1.16.10version>
????????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?{

????@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?{

????@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,?校驗失敗則拋出異常,?并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

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";

????@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

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
?????*/
????@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)?{
????????//?接口冪等性攔截器
????????registry.addInterceptor(apiIdempotentInterceptor());
????????super.addInterceptors(registry);
????}

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

}

OK, 目前為止, 校驗代碼準備就緒, 接下來測試驗證

七、測試驗證

1、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?{

????@Autowired
????private?TokenService?tokenService;

????@GetMapping
????public?ServerResponse?token()?{
????????return?tokenService.createToken();
????}

}

2、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?{

????@Autowired
????private?TestService?testService;

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

}

3、獲取token

查看redis

4、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

5、header或參數均不傳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)的刪除結果而直接放行, 那么還是會出現重復提交問題, 即使實際上只有一次真正的刪除操作, 下面重現一下

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果進行校驗, 所以還是有并發(fā)問題, 因此, 必須校驗

九、總結

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代碼, 其實也可以利用spring aop實現，無所謂。

Github

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

作者：wangzaiplus

www.jianshu.com/p/6189275403ed

?--END--



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Springboot + redis + 注解 + 攔截器來實現接口冪等性校驗