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28岁女生学前端开发难吗,河南seo,《网站开发实例》pdf下载,营销型网站主页定制1、目的使用lua脚本，可以保证多条命令的操作原子性；同时可以减少操作IO（比如说判断redis对应数据是否小于0，小于0就重置为100，这个场景一般是取出来再判断，再存放进行，就至少存在2次IO,用lua脚…

1、目的

使用lua脚本，可以保证多条命令的操作原子性；同时可以减少操作IO（比如说判断redis对应数据是否小于0，小于0就重置为100，这个场景一般是取出来再判断，再存放进行，就至少存在2次IO,用lua脚本一条命令1次IO就解决了,在批量扣减情况存在多次IO，lua脚本1次也可以解决），提高速度，降低IO.

2、使用案列

根据传入的产品标识及数量扣减该产品数量；此处为单个产品扣减，可优化为批量产品传入，lua内部用table处理。

2.1 初始化redis参数

添加产品及库存（hash结构）。添加两种水果的库存。

// 向Redis中添加数据
redisTemplate.opsForHash().put("productMap", "pro1", "{\"name\":\"苹果\",\"stock\":100}");
redisTemplate.opsForHash().put("productMap", "pro2", "{\"name\":\"西瓜\",\"stock\":1200}");

查看结果：

2.2 业务代码

传入lua脚本，实现对应产品库存数量扣减。(可优化为多产品批量扣减)

通过setnx加锁，防止死锁设置锁超时时间，同时业务执行完手动释放锁。设置锁等待时间、及锁等待轮询获取锁。(eg：自旋释放cpu资源重新抢占资源)

@Test
public void tete(){// 向Redis中添加数据redisTemplate.opsForHash().put("productMap", "pro1", "{\"name\":\"苹果\",\"stock\":100}");redisTemplate.opsForHash().put("productMap", "pro2", "{\"name\":\"西瓜\",\"stock\":1200}");// Lua 脚本字符串    String luaScript = "local productKey = KEYS[1]; " +"local pro = KEYS[2]; " +"local lockKey = KEYS[3]; " +"local lockTimeout = tonumber(ARGV[1]); " +"local deductAmount = tonumber(ARGV[2]); " +"local spinIntervalMs = tonumber(ARGV[3]); " +"local maxSpinCount = tonumber(ARGV[4]); " +"local lockAcquired = redis.call('setnx', lockKey, 1); " +"if lockAcquired == 1 then " +"    redis.call('pexpire', lockKey, lockTimeout); " +"    local currentValue = redis.call('hget', productKey, pro); " +"    if currentValue then " +"        local dbObj = cjson.decode(currentValue);" +"        local currentStock = tonumber(dbObj.stock); " +"        if currentStock >= deductAmount then " +"            dbObj.stock = currentStock - deductAmount; " +"            local updatedValue = cjson.encode(dbObj); " +"            redis.call('hset', productKey, pro, updatedValue); " +"            redis.call('del', lockKey); " +  // 释放锁"            return true; " +"        else " +"            return false; " +"        end " +"    else " +"        return false; " +"    end " +"else " +"    local spinCount = 0; " +"    while spinCount < maxSpinCount do " +"        local lockValue = redis.call('get', lockKey); " +"        if not lockValue then " +"            lockAcquired = redis.call('setnx', lockKey, 1); " +"            if lockAcquired == 1 then " +"                redis.call('pexpire', lockKey, lockTimeout); " +"                local currentValue = redis.call('hget', productKey, pro); " +"                if currentValue then " +"                   local dbObj = cjson.decode(currentValue);" +"                   local currentStock = tonumber(dbObj.stock); " +"                    if currentStock >= deductAmount then " +"                        dbObj.stock = currentStock - deductAmount; " +"                        local updatedValue = cjson.encode(dbObj); " +"                        redis.call('hset', productKey, pro, updatedValue); " +"                        redis.call('del', lockKey); " +  "                        return true; " +"                    else " +"                        return false; " +"                    end " +"                else " +"                    return false; " +"                end " +"            end " +"            break; " +"        end " +"        spinCount = spinCount + 1; " +"    end " +"    return false; " +"end";// 创建DefaultRedisScript对象DefaultRedisScript<Boolean> script = new DefaultRedisScript<>();script.setScriptText(luaScript);script.setResultType(Boolean.class); // 设置返回类型为Boolean// 执行脚本Boolean result = (Boolean) redisTemplate.execute(script,Collections.unmodifiableList(List.of("productMap","pro1","lock:pro1")), // KEYS参数"50000", // ARGV参数第一个：锁过期时间（毫秒）"10", // ARGV参数第二个：扣减数量"1000",// ARGV参数第3个：等待时间"5");// ARGV参数第4个：轮询次数System.out.println("result1:"+result);Boolean result2 = (Boolean) redisTemplate.execute(script,Collections.unmodifiableList(List.of("productMap","pro1","lock:pro1")), // KEYS参数"50000", // ARGV参数第一个：锁过期时间（毫秒）"10", // ARGV参数第二个：扣减数量"1000","5");System.out.println("result2:"+result2);Boolean result3 = (Boolean) redisTemplate.execute(script,Collections.unmodifiableList(List.of("productMap","pro1","lock:pro1")), // KEYS参数"50000", // ARGV参数第一个：锁过期时间（毫秒）"10", // ARGV参数第二个：扣减数量"1000","5");System.out.println("result3:"+result3);if (result2) {System.out.println("Stock deduction successful.");} else {System.out.println("Insufficient stock or lock already acquired.");}// 验证库存是否正确扣减Object updatedValue = redisTemplate.opsForHash().get("productMap", "pro1");System.out.println(updatedValue);Boolean result5 = (Boolean) redisTemplate.execute(script,Collections.unmodifiableList(List.of("productMap","pro2","lock:pro2")), // KEYS参数"5000", // ARGV参数第一个：锁过期时间（毫秒）"500", // ARGV参数第二个：扣减数量"1000","5");
}