<properties>
    <java.version>1.8</java.version>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
    <spring-boot.version>2.3.12.RELEASE</spring-boot.version>
</properties>
<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-redis</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
    </dependency>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <optional>true</optional>
    </dependency>
    <dependency>
        <groupId>com.baomidou</groupId>
        <artifactId>mybatis-plus-boot-starter</artifactId>
        <version>3.5.2</version>
    </dependency>
</dependencies>

create database t_desc collate utf8mb4_general_ci;
use t_desc;
create table t_good (
    id bigint auto_increment primary key comment '自增id',
    good_name varchar(255) not null comment '商品名稱',
    stock int not null comment '商品庫(kù)存'
) comment '庫(kù)存測(cè)試表';
insert into t_good(good_name, stock)  value('iphone', 50);

<update id="descGoodStock">
  update t_desc.t_good
  set t_good.stock = t_good.stock - 1
  where id = #{id}
</update>

<update id="descGoodStockByLock">
        update t_desc.t_good
        set t_good.stock = t_good.stock - 1
        where id = #{id}
          and t_good.stock > 0
</update>

@PostMapping("/db")
public Map<String, Object> goodDescControllerByDataBase(Long id) {
    HashMap<String, Object> ret = new HashMap<>();
    // 查出舊的值
    Good good = goodMapper.selectStockById(id);
    // 再進(jìn)行更新
    int i = goodMapper.descGoodStockCAS(id, good.getStock());
    if (i > 1) {
        ret.put("info", "success, 扣減成功");
    } else {
        ret.put("info", "fail, 扣減失敗");
    }
    return ret;
}

<update id="descGoodStockCAS">
        update t_desc.t_good
        set t_good.stock = t_good.stock - 1
        where id = #{id}
          and t_good.stock = #{stock}
          and t_good.stock > 0
    </update>

 @PostMapping("/redis")
    public Map<String, Object> goodDescControllerByRedis(Long id) throws InterruptedException {
        HashMap<String, Object> ret = new HashMap<>();
        ret.put("info", "fail, 扣減失敗");
        // 查詢 Redis 中的庫(kù)存
        Integer stock = (Integer) redisTemplate.opsForValue().get(key + id);
        Thread.sleep(100);
        if (stock <= 0) {
            return ret;
        }
        // 扣減 redis 中庫(kù)存
        Long decrement = redisTemplate.opsForValue().decrement(key + id);
        if (decrement >= 0) {
            // 扣減數(shù)據(jù)庫(kù)庫(kù)存
            goodMapper.descGoodStock(id);
            ret.put("info", "success, 扣減成功");
        }
        return ret;
    }

---
--- Generated by EmmyLua(https://github.com/EmmyLua)
--- Created by Ezreal.
--- DateTime: 2023/5/6 21:56
---
if (redis.call('exists', KEYS[1]) == 1) then
    local stock = tonumber(redis.call('get', KEYS[1]));
    if (stock <= 0) then
        return -1;
    end
    if (stock > 0) then
        redis.call('incrby', KEYS[1], -1);
        return 1;
    end
end
return -1

private static final DefaultRedisScript<Long> DECREASE_GOOD_STOCK_SCRIPT = new DefaultRedisScript<>();
static {
    DECREASE_GOOD_STOCK_SCRIPT.setLocation(new ClassPathResource("/lua/desc_stock.lua"));
    // 設(shè)置返回值類型
    DECREASE_GOOD_STOCK_SCRIPT.setResultType(Long.class);
}
@PostMapping("/lua")
public Map<String, Object> goodDescControllerByLUA(Long id) {
    List<String> keys = new ArrayList<>();
    keys.add("stock:" + id);
    HashMap<String, Object> ret = new HashMap<>();
    ret.put("info", "fail, 扣減失敗");
    Long execute = redisTemplate.execute(DECREASE_GOOD_STOCK_SCRIPT, keys);
    if (execute == 1) {
        goodMapper.descGoodStock(id);
        ret.put("info", "success, 扣減成功");
    }
    return ret;
}

@PostMapping("/lock")
public Map<String, Object> goodDescControllerByLock(Long id) throws InterruptedException {
    HashMap<String, Object> ret = new HashMap<>();
    ret.put("info", "fail, 扣減失敗");
    // 加鎖
    RLock lock = redissonClient.getLock("stock" + id);
    boolean tryLock = lock.tryLock(2L, 1L, TimeUnit.SECONDS);
    if (tryLock) {
        Integer stock = (Integer) redisTemplate.opsForValue().get(key + id);
        if (stock <= 0) {
            return ret;
        }
        Long decrement = redisTemplate.opsForValue().decrement(key + id);
        if (decrement >= 0) {
            goodMapper.descGoodStock(id);
            ret.put("info", "success, 扣減成功");
        }
    }
    return ret;
}