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

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.6.4</version><relativePath/> <!-- lookup parent from repository --></parent><groupId>com.hmblogs</groupId><artifactId>hmblogs</artifactId><version>0.0.1-SNAPSHOT</version><name>hmblogs</name><description>hmblogs</description><properties><java.version>8</java.version><druid.version>1.2.8</druid.version><log4jdbc.version>1.16</log4jdbc.version></properties><dependencies><!-- druid数据源驱动 --><dependency><groupId>com.alibaba</groupId><artifactId>druid-spring-boot-starter</artifactId><version>${druid.version}</version></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency><!-- mybatis --><dependency><groupId>com.baomidou</groupId><artifactId>mybatis-plus-boot-starter</artifactId><version>3.5.3.1</version></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><optional>true</optional></dependency><!--Mysql依赖包--><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><scope>runtime</scope></dependency><!--lombok插件--><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><optional>true</optional></dependency><!--监控sql日志--><dependency><groupId>org.bgee.log4jdbc-log4j2</groupId><artifactId>log4jdbc-log4j2-jdbc4.1</artifactId><version>${log4jdbc.version}</version></dependency><dependency><groupId>com.alibaba</groupId><artifactId>fastjson</artifactId><version>1.2.9</version></dependency><dependency><groupId>redis.clients</groupId><artifactId>jedis</artifactId></dependency></dependencies><build><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId></plugin></plugins></build></project>

3、应用配置文件

server:port: 8081servlet.context-path: /#配置数据源
spring:datasource:druid:db-type: com.alibaba.druid.pool.DruidDataSourcedriverClassName: net.sf.log4jdbc.sql.jdbcapi.DriverSpyurl: jdbc:log4jdbc:mysql://${DB_HOST:localhost}:${DB_PORT:3306}/${DB_NAME:eladmin}?serverTimezone=Asia/Shanghai&characterEncoding=utf8&useSSL=falseusername: ${DB_USER:root}password: ${DB_PWD:123456}

4、StockMapper.xml如下

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="com.hmblogs.backend.dao.StockMapper"><resultMap id="BaseResultMap" type="com.hmblogs.backend.entity.Stock"><id column="id" property="id"/><result column="quantity" property="quantity"/></resultMap><sql id="BaseResultMap">id, quantity</sql><select id="findAll" resultMap="BaseResultMap">select<include refid="BaseResultMap"/>from t_stock</select><select id="findById" resultMap="BaseResultMap"  parameterType="com.hmblogs.backend.entity.Stock">select<include refid="BaseResultMap"/>from t_stockwhere id=#{id}</select><update id="updateStockById" parameterType="com.hmblogs.backend.entity.Stock">update t_stock set quantity=quantity-1 where id=#{id}</update>
</mapper>

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<Stock> {List<Stock> 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 {@Autowiredprivate 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<String> qiangdan() {//抢到商品的用户List<String> shopUsers = new ArrayList<>();//构造很多用户List<String> 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 {@Autowiredprivate 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。