SpringBoot + Redis 解决重复提交问题（幂等）

在开发中，一个对外暴露的接口可能会面临瞬间的大量重复请求，如果想过滤掉重复请求造成对业务的伤害，那就需要实现幂等

幂等：

• 任意多次执行所产生的影响均与一次执行的影响相同。最终的含义就是 对数据库的影响只能是一次性的，不能重复处理。

解决方案：

1. 数据库建立唯一性索引，可以保证最终插入数据库的只有一条数据
2. token机制，每次接口请求前先获取一个token，然后再下次请求的时候在请求的header体中加上这个token，后台进行验证，如果验证通过删除token，下次请求再次判断token（本次案例使用）
3. 悲观锁或者乐观锁，悲观锁可以保证每次for update的时候其他sql无法update数据(在数据库引擎是innodb的时候,select的条件必须是唯一索引,防止锁全表)
4. 先查询后判断，首先通过查询数据库是否存在数据，如果存在证明已经请求过了，直接拒绝该请求，如果没有存在，就证明是第一次进来，直接放行

一、搭建Redis服务

package com.gamer.idempotence.service;

/**
 * @author 47
 * @version 1.0
 * @date 2020/6/11 9:42
 * @description: redis工具类
 */

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.core.ValueOperations;
import org.springframework.data.redis.serializer.RedisSerializer;
import org.springframework.data.redis.serializer.StringRedisSerializer;
import org.springframework.stereotype.Component;

import java.io.Serializable;
import java.util.concurrent.TimeUnit;

/**
 * redis工具类
 */
@Component
public class RedisService {

    private RedisTemplate redisTemplate;

    @Autowired(required = false)
    public void setRedisTemplate(RedisTemplate redisTemplate) {
        RedisSerializer stringSerializer = new StringRedisSerializer();
        redisTemplate.setKeySerializer(stringSerializer);
        redisTemplate.setValueSerializer(stringSerializer);
        redisTemplate.setHashKeySerializer(stringSerializer);
        redisTemplate.setHashValueSerializer(stringSerializer);
        this.redisTemplate = redisTemplate;
    }

    /**
     * 写入缓存
     *
     * @param key
     * @param value
     * @return
     */

    public boolean set(final String key, Object value) {
        boolean result = false;
        try {
            ValueOperations operations = redisTemplate.opsForValue();
            operations.set(key, value);
            result = true;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return result;
    }

    /**
     * 写入缓存设置时效时间
     *
     * @param key
     * @param value
     * @return
     */

    public boolean setEx(final String key, Object value, Long expireTime) {
        boolean result = false;
        try {
            ValueOperations<Serializable, Object> operations = redisTemplate.opsForValue();
            operations.set(key, value);
            redisTemplate.expire(key, expireTime, TimeUnit.SECONDS);
            result = true;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return result;
    }

    /**
     * 判断缓存中是否有对应的value
     *
     * @param key
     * @return
     */
    public boolean exists(final String key) {
        return redisTemplate.hasKey(key);
    }


    /**
     * 读取缓存
     * @param key
     * @return
     */
    public Object get(final String key) {
        Object o = null;
        ValueOperations valueOperations = redisTemplate.opsForValue();
        return valueOperations.get(key);
    }


    /**
     * 删除对应的value
     * @param key
     */
    public Boolean remove(final String key) {
        if(exists(key)){
            return redisTemplate.delete(key);
        }
        return false;
    }

}

二、自定义注解

作用：拦截器拦截请求时，判断调用的地址对应的Controller方法是否有自定义注解，有的话说明该接口方法进行 幂等

package com.gamer.idempotence.annotion;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * @author 47
 * @version 1.0
 * @date 2020/6/11 9:55
 * @description:
 */
@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface AutoIdempotent {
}

三、Token创建和校验

package com.gamer.idempotence.service;

import com.gamer.idempotence.exectionhandler.BaseException;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.util.StringUtils;

import javax.servlet.http.HttpServletRequest;
import java.util.UUID;

/**
 * @author 47
 * @version 1.0
 * @date 2020/6/11 9:56
 * @description: token服务
 */
@Service
public class TokenService {

    @Autowired RedisService redisService;

    //创建token
    public String createToken() {
        //使用UUID代表token
        UUID uuid = UUID.randomUUID();
        String token = uuid.toString();
        //存入redis
        boolean b = redisService.setEx(token, token, 10000L);
        return token;
    }

    //检验请求头或者请求参数中是否有token
    public boolean checkToken(HttpServletRequest request) {

        String token = request.getHeader("token");

        //如果header中是空的
        if(StringUtils.isEmpty(token)){

            //从request中拿
            token = request.getParameter("token");
            if(StringUtils.isEmpty(token)){
               throw new BaseException(20001, "缺少参数token");
            }

        }

        //如果从header中拿到的token不正确
        if(!redisService.exists(token)){
            throw new BaseException(20001, "不能重复提交-------token不正确、空");
        }

        //token正确 移除token
        if(!redisService.remove(token)){
            throw new BaseException(20001, "token移除失败");
        }

        return true;
    }
}

这里用到了自定义异常和自定义响应体如下

自定义异常：

package com.gamer.idempotence.exectionhandler;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

/**
 * @author 47
 * @version 1.0
 * @date 2020/5/16 20:58
 * @description: 自定义异常类
 */
@Data
@AllArgsConstructor
@NoArgsConstructor
public class BaseException extends RuntimeException {

    private Integer code;

    private String msg;

}

设置统一异常处理：

package com.gamer.idempotence.exectionhandler;


import com.gamer.idempotence.utils.R;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.ResponseBody;

/**
 * @author 47
 * @version 1.0
 * @date 2020/5/16 20:45
 * @description: 统一异常处理器
 */
@ControllerAdvice
public class GlobalExceptionHandler {

    @ExceptionHandler(Exception.class)
    @ResponseBody
    public R error(Exception e){
        e.printStackTrace();
        return R.error();
    }

    @ExceptionHandler(BaseException.class)
    @ResponseBody
    public R error(BaseException e){
        e.printStackTrace();
        return R.error().message(e.getMsg()).code(e.getCode());
    }
}

自定义响应体：

package com.gamer.idempotence.utils;

import lombok.Data;

import java.util.HashMap;
import java.util.Map;

/**
 * @author 47
 * @version 1.0
 * @date 2020/5/16 18:35
 * @description: 返回结果
 */
@Data
public class R {

    private Boolean success;
    private Integer code;
    private String message;
    private Map<String, Object> data = new HashMap<String, Object>();

    private R() {
    }

    //封装返回成功
    public static R ok(){
        R r = new R();
        r.setSuccess(true);
        r.setCode(ResultCode.SUCCESS);
        r.setMessage("成功");
        return r;
    }

    //封装返回失败
    public static R error(){
        R r = new R();
        r.setSuccess(false);
        r.setCode(ResultCode.ERROR);
        r.setMessage("失败");
        return r;
    }

    public R success(Boolean success){
        this.setSuccess(success);
        return this;
    }
    public R message(String message){
        this.setMessage(message);
        return this;
    }
    public R code(Integer code){
        this.setCode(code);
        return this;
    }
    public R data(String key, Object value){
        this.data.put(key, value);
        return this;
    }
    public R data(Map<String, Object> map){
        this.setData(map);
        return this;
    }
}

自定义响应码：

package com.gamer.idempotence.utils;

import lombok.Data;

import java.util.HashMap;
import java.util.Map;

/**
 * @author 47
 * @version 1.0
 * @date 2020/5/16 18:35
 * @description: 返回结果
 */
@Data
public class R {

    private Boolean success;
    private Integer code;
    private String message;
    private Map<String, Object> data = new HashMap<String, Object>();

    private R() {
    }

    //封装返回成功
    public static R ok(){
        R r = new R();
        r.setSuccess(true);
        r.setCode(ResultCode.SUCCESS);
        r.setMessage("成功");
        return r;
    }

    //封装返回失败
    public static R error(){
        R r = new R();
        r.setSuccess(false);
        r.setCode(ResultCode.ERROR);
        r.setMessage("失败");
        return r;
    }

    public R success(Boolean success){
        this.setSuccess(success);
        return this;
    }
    public R message(String message){
        this.setMessage(message);
        return this;
    }
    public R code(Integer code){
        this.setCode(code);
        return this;
    }
    public R data(String key, Object value){
        this.data.put(key, value);
        return this;
    }
    public R data(Map<String, Object> map){
        this.setData(map);
        return this;
    }
}

四、拦截器配置

1、拦截器配置类

package com.gamer.idempotence.config;

import com.gamer.idempotence.interceptor.AutoIdempotentInterceptor;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

/**
 * @author 47
 * @version 1.0
 * @date 2020/6/11 10:07
 * @description: 拦截器配置类
 */
@Configuration
public class WebConfiguration implements WebMvcConfigurer {

    @Autowired
    private AutoIdempotentInterceptor autoIdempotentInterceptor;

    @Override
    public void addInterceptors(InterceptorRegistry registry) {

        registry.addInterceptor(autoIdempotentInterceptor);

    }
}

2、拦截器类

package com.gamer.idempotence.interceptor;

import com.gamer.idempotence.annotion.AutoIdempotent;
import com.gamer.idempotence.service.TokenService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.HandlerInterceptor;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.lang.reflect.Method;

/**
 * @author 47
 * @version 1.0
 * @date 2020/6/11 10:11
 * @description: 拦截重复提交数据
 */
@Component
public class AutoIdempotentInterceptor implements HandlerInterceptor {

    @Autowired
    private TokenService tokenService;

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {


        if(!(handler instanceof HandlerMethod))
            return true;
        HandlerMethod handlerMethod = (HandlerMethod) handler;
        Method method = handlerMethod.getMethod();

        //拿到方法上面的自定义注解
        AutoIdempotent annotation = method.getAnnotation(AutoIdempotent.class);
        
        //如果不等于null说明该方法要进行幂等
        if(null != annotation){
            return tokenService.checkToken(request);
        }

        return true;
    }
}

五、正常Sevice类

package com.gamer.idempotence.service;

import org.springframework.stereotype.Service;

/**
 * @author 47
 * @version 1.0
 * @date 2020/6/11 10:04
 * @description:
 */
@Service
public class TestService {

    public String testMethod(){
        return "正常业务逻辑";
    }

}

六、Controller类

package com.gamer.idempotence.controller;

import com.gamer.idempotence.annotion.AutoIdempotent;
import com.gamer.idempotence.service.TestService;
import com.gamer.idempotence.service.TokenService;
import com.gamer.idempotence.utils.R;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

/**
 * @author 47
 * @version 1.0
 * @date 2020/6/11 9:58
 * @description:
 */
@RestController
@CrossOrigin
@RequestMapping("/Idempotence")
public class TestController {

    @Autowired
    private TokenService tokenService;

    @Autowired
    private TestService testService;


    @GetMapping("/getToken")
    public R getToken(){
        String token = tokenService.createToken();
        return R.ok().data("token",token);
    }


    //相当于添加数据接口（测试时 连续点击添加数据按钮  看结果是否是添加一条数据还是多条数据）
    @AutoIdempotent
    @PostMapping("/test/addData")
    public R addData(){
        String s = testService.testMethod();
        return R.ok().data("data",s);
    }





}

七、测试

第一次点击：

 第二次点击：