lua脚本实现redis命令decrby减至最小为0

1、lua脚本decrby.lua

local current = redis.call('get', KEYS[1]);
if current == false then
    return nil;
end
if tonumber(ARGV[1]) > tonumber(current) then
    return redis.call('decrby', KEYS[1], current);
else
    return redis.call('decrby', KEYS[1], ARGV[1]);
end

2、RedisLuaUtil.java
1）直接在代码中写lua脚本字符串

package com.example.demo;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.core.script.DefaultRedisScript;
import org.springframework.stereotype.Component;

import javax.annotation.Resource;
import java.util.ArrayList;
import java.util.List;

/**
 * redis lua工具类
 * @author xuzhipeng
 * @date 2021/01/31
 */
@Component
public class RedisLuaUtil {

    private static final Logger log = LoggerFactory.getLogger(RedisLuaUtil.class);

    private static final String LUA_SCRIPT_DECRBY_UNTIL_TO_0 = "local current = redis.call('get', KEYS[1]);" +
            "if current == false then " +
            "    return nil;" +
            "end " +
            "if tonumber(ARGV[1]) > tonumber(current) then " +
            "    return redis.call('decrby', KEYS[1], current);" +
            "else " +
            "    return redis.call('decrby', KEYS[1], ARGV[1]);" +
            "end";
    
    @Resource
    private RedisTemplate redisTemplate;
   
    /**
     * Decrby 命令将 key 所储存的值减去指定的减量值。（减至最小值为0）
     * @param key
     * @param delta
     * @return 当key不存在时返回null;key存在,当前值<delta时,减去当前值;key存在,当前值>=delta时,减去delta;
     */
    public Long decrByUntilTo0(String key, long delta){
        List<String> keyList = new ArrayList<>();
        keyList.add(key);
        DefaultRedisScript<Long> redisScript = new DefaultRedisScript<>(LUA_SCRIPT_DECRBY_UNTIL_TO_0,Long.class);
        Long result = null;
        try {
            result = (Long) redisTemplate.execute(redisScript,keyList,delta);
        } catch (Exception e) {
             log.error("decrby异常",e);
        }
        return result;
    }
}

2）引用lua脚本文件

    /**
     * Decrby 命令将 key 所储存的值减去指定的减量值。（减至最小值为0）
     * @param key
     * @param delta
     * @return 当key不存在时返回null;key存在,当前值<delta时,减去当前值;key存在,当前值>=delta时,减去delta;
     */
    public Long decrByUntilTo0(String key, long delta){
        List<String> keyList = new ArrayList<>();
        keyList.add(key);
        DefaultRedisScript<Long> redisScript = new DefaultRedisScript<>();
        redisScript.setScriptSource(new ResourceScriptSource(new ClassPathResource("lua/decrby.lua")));
        redisScript.setResultType(Long.class);
        Long result = null;
        try {
            result = (Long) redisTemplate.execute(redisScript,keyList,delta);
        } catch (Exception e) {
            log.error("decrby异常",e);
        }
        return result;
    }