Sprinig Boot + Redis 如何实现接口幂等性

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 

可能出现的问题：

• 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

• 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

解决方案：

1. 唯一索引 -- 防止新增脏数据

2. token机制 -- 防止页面重复提交

3. 悲观锁 -- 获取数据的时候加锁(锁表或锁行)

4. 乐观锁 -- 基于版本号version实现, 在更新数据那一刻校验数据

5. 分布式锁 -- redis(jedis、redisson)或zookeeper实现

6. 状态机 -- 状态变更, 更新数据时判断状态

为需要保证幂等性的每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

项目技术栈

• 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

六、代码实现

1. 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, 自定义log即可-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.16.10</version>
        </dependency>

1. 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();
    }

    /**
     * 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();
        }
    }

}

1. 自定义注解@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 {
}

1. ApiIdempotentInterceptor拦截器

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 {
    }
}

1. 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());
        }
    }

}

1. 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

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();
    }

}

1. 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

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();
    }

}

1. 获取token

   

查看redis

1. 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

   

1. 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"

   

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

稍微修改一下代码:

再次请求

再看看控制台

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。