spring boot学习第八篇:通过spring boot、jedis实现秒单

参考：Redis实现分布式锁的7种方案 - 知乎

1、 准备数据库表，如下SQL表示库存表，有主键ID和库存数量字段

CREATE TABLE `t_stock` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `quantity` bigint(20) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin;

初始数据id           quantity

              1111       9

2、pom.xml文件

    4.0.0
    
        org.springframework.boot
        spring-boot-starter-parent
        2.6.4
         
    
    com.hmblogs
    hmblogs
    0.0.1-SNAPSHOT
    hmblogs
    hmblogs
    
        8
        1.2.8
        1.16
    
    
        
        
            com.alibaba
            druid-spring-boot-starter
            ${druid.version}
        

        
            org.springframework.boot
            spring-boot-starter
        

        
            org.springframework.boot
            spring-boot-starter-test
            test
        

        
        
            com.baomidou
            mybatis-plus-boot-starter
            3.5.3.1
        

        
            org.springframework.boot
            spring-boot-starter-web
        

        
            org.projectlombok
            lombok
            true
        

        
        
            mysql
            mysql-connector-java
            runtime
        

        
        
            org.projectlombok
            lombok
            true
        

        
        
            org.bgee.log4jdbc-log4j2
            log4jdbc-log4j2-jdbc4.1
            ${log4jdbc.version}
        

        
            com.alibaba
            fastjson
            1.2.9
        

        
            redis.clients
            jedis
        

    

    
        
            
                org.springframework.boot
                spring-boot-maven-plugin
            
        
    

3、应用配置文件

server:
  port: 8081
  servlet.context-path: /

#配置数据源
spring:
  datasource:
    druid:
      db-type: com.alibaba.druid.pool.DruidDataSource
      driverClassName: net.sf.log4jdbc.sql.jdbcapi.DriverSpy
      url: jdbc:log4jdbc:mysql://${DB_HOST:localhost}:${DB_PORT:3306}/${DB_NAME:eladmin}?serverTimezone=Asia/Shanghai&characterEncoding=utf8&useSSL=false
      username: ${DB_USER:root}
      password: ${DB_PWD:123456}

4、StockMapper.xml如下

    
        
        
    

    
        id, quantity
    

    
        select
        
        from t_stock

    

    
        select
        
        from t_stock
        where id=#{id}
    

    
        update t_stock set quantity=quantity-1 where id=#{id}
    

5、BackendApplication

package com.hmblogs.backend;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class BackendApplication {

    public static void main(String[] args) {
        SpringApplication.run(BackendApplication.class, args);
    }

}

6、Stock.java如下

package com.hmblogs.backend.entity;


import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.Data;

@Data
@TableName("t_stock")
public class Stock {

    @TableId(value="id", type = IdType.AUTO)
    private Integer id;

    private Integer quantity;

}

7、StockMapper

package com.hmblogs.backend.dao;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.hmblogs.backend.entity.Stock;
import org.apache.ibatis.annotations.Mapper;

import java.util.List;

@Mapper
public interface StockMapper extends BaseMapper {
    List findAll();

    Stock findById(Stock stock);

    Integer updateStockById(Stock stock);
}

8、OrderController

package com.hmblogs.backend.controller;

import com.hmblogs.backend.dao.StockMapper;
import com.hmblogs.backend.entity.Stock;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.util.StringUtils;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import redis.clients.jedis.Jedis;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.TimeUnit;
import java.util.stream.IntStream;

@RestController
@Slf4j
public class OrderController {

    @Autowired
    private StockMapper stockMapper;

    //总库存
    private long nKuCuen = 0;
    //商品key名字
    private String shangpingKey = "computer_key";
    //获取锁的超时时间 秒
    private int timeout = 30 * 1000;

    @GetMapping("/qiangdan")
    public List qiangdan() {

        //抢到商品的用户
        List shopUsers = new ArrayList<>();

        //构造很多用户
        List users = new ArrayList<>();
        IntStream.range(0, 10000).parallel().forEach(b -> {
            users.add("神牛-" + b);
        });

        //初始化库存
        nKuCuen = 10;

        //模拟开抢
        users.parallelStream().forEach(b -> {
            String shopUser = qiang(b);
            if (!StringUtils.isEmpty(shopUser)) {
                shopUsers.add(shopUser);
            }
        });

        return shopUsers;
    }

    /**
     * 模拟抢单动作
     *
     * @param b
     * @return
     */
    private String qiang(String b) {
        //用户开抢时间
        long startTime = System.currentTimeMillis();

        //未抢到的情况下，30秒内继续获取锁
        while ((startTime + timeout) >= System.currentTimeMillis()) {
            //商品是否剩余
            if (nKuCuen <= 0) {
                break;
            }
            Jedis jedisCom = new Jedis("localhost",6379);
            jedisCom.auth("heming");
            if (jedisCom.setnx(shangpingKey, b)==1) {
                //用户b拿到锁
                log.info("用户{}拿到锁...", b);
                try {
                    //商品是否剩余
                    if (nKuCuen <= 0) {
                        break;
                    }

                    //模拟生成订单耗时操作，方便查看：神牛-50 多次获取锁记录
                    try {
                        TimeUnit.SECONDS.sleep(1);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }

                    //抢购成功，商品递减，记录用户
                    nKuCuen -= 1;
                    int id = 1111;
                    Stock stock = new Stock();
                    stock.setId(id);
                    Stock stockDo = stockMapper.findById(stock);
                    Integer quantity = stockDo.getQuantity();
                    if(quantity!=null && quantity>0){
                        stockMapper.updateStockById(stock);
                        log.info("update success.");
                    }else{
                        log.info("no update.");
                    }

                    //抢单成功跳出
                    log.info("用户{}抢单成功跳出...所剩库存：{}", b, nKuCuen);

                    return b + "抢单成功，所剩库存：" + nKuCuen;
                } finally {
                    log.info("用户{}释放锁...", b);
                    //释放锁
                    jedisCom.del(shangpingKey, b);
                }
            }
        }
        return "";
    }

}

9、验证

浏览器访问http://localhost:8081/qiangdan

查看Idea的console内容，

 将console内容拿到notepad++里面搜索

但是，搜索"update success."内容，预期是9次，实际也是9次，符合我的需要，没有让库存变成负数，

 查看数据库表的库存，id为1111的记录的quantity为0，不是1，也不是负数

10、继续第二种纬度的验证 

StockController的代码如下：

package com.hmblogs.backend.controller;

import com.hmblogs.backend.dao.StockMapper;
import com.hmblogs.backend.entity.Stock;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import redis.clients.jedis.Jedis;
import java.util.Date;

@RestController
@Slf4j
public class StockController {

    @Autowired
    private StockMapper stockMapper;

    /**
     * redis test
     * @return
     */
    @GetMapping(value = "/reduceStock")
    public void redisTestLock(){
        log.info("reduceStock");
        int id = 1111;
        String key = "reduceStock"+id;
        String time = new Date().getTime()+"";
        Jedis jedisCom = new Jedis("localhost",6379);
        jedisCom.auth("heming");
        if (jedisCom.setnx(key, time)==1) {
            log.info("{}生成锁...", time);
            try{
                Stock stock = new Stock();
                stock.setId(id);
                Stock stockDo = stockMapper.findById(stock);
                Integer quantity = stockDo.getQuantity();
                if(quantity!=null && quantity>0){
                    stockMapper.updateStockById(stock);
                    log.info("update success.");
                }else{
                    log.info("no update.");
                }
            } finally {
                log.info("{}释放锁...", time);
                //释放锁
                jedisCom.del(key, time);
            }
        }
    }
}

将库存改为10，验证，通过压测验证有没有保证锁应该有的作用，控制查库存和当不小于0的时候减少库存这2个逻辑的原子性，预期做到，实际做到了。利用APIPost工具做压测，如下图所示

查看server的控制台

 

 然后把这些内容复制到notepad++里面搜索，

搜索reduceStock，有100个结果

搜索"生成锁..."和"释放锁..."，都有14次结果，说明jedisCom.setnx(key, time)==1成立的次数有14次。

 搜索"update success."，有10次结果，说明减少库存减少了10次，

此时查看数据库表的库存，发现为0

 搜索"no update."，发现有4个结果，说明有4次获得锁了，但是库存已经是0了，不能再减库存了，库存不能为负的。