[Redis] Redis--EVAL

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💌EVAL帮助文档

EVAL-Redis命令参考

传参数的格式

其中 "return {KEYS[1],KEYS[2],ARGV[1],ARGV[2]}" 是被求值的 Lua 脚本，数字 2 指定了键名参数的数量， key1 和 key2 是键名参数，分别使用 KEYS[1] 和 KEYS[2] 访问，而最后的 argv1 和 argv2 则是附加参数，可以通过 ARGV[1] 和 ARGV[2] 访问它们

• redis.call()

• eval执行scan

源生scan命令

1.  
   //例如模糊迭代初始游标为0 前缀为'user.'的Key 期望获取5条的命令
2.  
   scan 0 match user.* count 5

使用eval执行脚本

eval "return redis.call('scan',ARGV[1],'match',KEYS[1],'count',ARGV[2])" 1 user.* 0 5

💌SpringBoot调用LUA脚本 

1.  
   @SpringBootTest
2.  
   public class AppTests_Lua {
3.  
    
4.  
   @Resource(name = "redisTemplate")
5.  
   private ValueOperations<String, User> valueOperations;
6.  
    
7.  
   @Autowired
8.  
   private StringRedisTemplate stringRedisTemplate;
9.  
    
10.  
    @Test
11.  
    void test1() {
12.  
    for (int i =1 ;i<11;i ){
13.  
    User user = User.builder().name(i "号张").age(18).build();
14.  
    valueOperations.set("user." i,user);
15.  
    }
16.  
    }
17.  
    @Test
18.  
    void test2(){
19.  
    String lua = "return redis.call('scan',ARGV[1],'match',KEYS[1],'count',ARGV[2])";
20.  
    RedisScript<List> redisScript = RedisScript.of(lua,List.class);
21.  
    List<String> keys = new ArrayList<>();
22.  
    keys.add("user.*");
23.  
    List execute = stringRedisTemplate.execute(redisScript, keys, "0", "5");
24.  
    }
25.  
    }

完整的迭代过程

1.  
   @Test
2.  
   void test2() {
3.  
   String lua = "return redis.call('scan',ARGV[1],'match',KEYS[1],'count',ARGV[2])";
4.  
   RedisScript<List> redisScript = RedisScript.of(lua, List.class);
5.  
   List<String> keys = new ArrayList<>();
6.  
   keys.add("user.*");
7.  
   String cursor = "0";
8.  
   do {
9.  
   List results = stringRedisTemplate.execute(redisScript, keys, cursor, "5");
10.  
    cursor = (String) results.get(0);
11.  
    List<String> results_keys = (List<String>) results.get(1);
12.  
    System.out.println(cursor);
13.  
    System.out.println(results_keys);
14.  
    } while (!"0".equals(cursor));
15.  
    }

 简单的get两种方式(KEYS提前预编译好了,与ARGV的区别只是效率不同)

1.  
   @Test
2.  
   void test3() {
3.  
   String lua = "return redis.call('mget',KEYS[1],KEYS[2])";
4.  
   RedisScript<List> redisScript = RedisScript.of(lua, List.class);
5.  
   List<String> keys = new ArrayList<>();
6.  
   keys.add("user.1");
7.  
   keys.add("user.10");
8.  
   List results = stringRedisTemplate.execute(redisScript, keys);
9.  
   }

1.  
   @Test
2.  
   void test3() {
3.  
   String lua = "return redis.call('mget',ARGV[1],ARGV[2])";
4.  
   RedisScript<List> redisScript = RedisScript.of(lua, List.class);
5.  
   List<String> keys = new ArrayList<>();
6.  
   List results = stringRedisTemplate.execute(redisScript, keys,"user.1","user.10");
7.  
   }

💌解决库存负数问题

1.  
   @SpringBootTest
2.  
   class AppTests_DecrBy {
3.  
    
4.  
   @Resource(name = "redisTemplate")
5.  
   private ValueOperations<String, Integer> valueOperations;
6.  
    
7.  
   @Autowired
8.  
   private StringRedisTemplate stringRedisTemplate;
9.  
    
10.  
    //定义一个产品
11.  
    private final static String productKey = "product01";
12.  
     
13.  
    @Test
14.  
    void test1() throws InterruptedException {
15.  
    //设置初始化库存5个
16.  
    valueOperations.set(productKey, 5);
17.  
    //获取线程池
18.  
    ExecutorService executorService = Executors.newCachedThreadPool();
19.  
    //模拟开启10个线程
20.  
    for (int i = 1; i <= 10; i ) {
21.  
    //模拟扣减i个库存量(qty)
22.  
    int finalI = i;
23.  
    //开启线程执行
24.  
    executorService.execute(() -> {
25.  
    doing(finalI);
26.  
    });
27.  
    }
28.  
    //防止主线程停止,导致模拟线程不执行
29.  
    Thread.sleep(60 * 1000);
30.  
    }
31.  
    //lua脚本语言
32.  
    private static String lua ;
33.  
    static {
34.  
    StringBuilder sb = new StringBuilder();
35.  
    sb.append(" local key = KEYS[1] ");
36.  
    sb.append(" local qty = ARGV[1] ");
37.  
    sb.append(" local redis_qty = redis.call('get',key) ");
38.  
    sb.append(" if tonumber(redis_qty) >= tonumber(qty) ");
39.  
    sb.append(" then ");
40.  
    sb.append(" redis.call('decrby',key,qty) ");
41.  
    sb.append(" return -1 ");
42.  
    sb.append(" else ");
43.  
    sb.append(" return tonumber(redis_qty) ");
44.  
    sb.append(" end ");
45.  
    lua = sb.toString();
46.  
    }
47.  
     
48.  
    private void doing(Integer qty){
49.  
    RedisScript<Long> redisScript = RedisScript.of(lua,Long.class);
50.  
    List<String> keys = new ArrayList<>();
51.  
    keys.add(productKey);
52.  
    Long ret = stringRedisTemplate.execute(redisScript, keys,qty.toString());
53.  
    if(ret.intValue()==-1){
54.  
    System.out.println(StrUtil.format("{},扣减成功,扣减数量:{}",Thread.currentThread().getName(),qty));
55.  
    }else{
56.  
    System.out.println(StrUtil.format("{},库存不足,需求量:{},库存量:{}",Thread.currentThread().getName(),qty,ret));
57.  
    }
58.  
    }
59.  
    }

核心代码逻辑

1.  
   //lua脚本语言
2.  
   //local定义变量的修饰符
3.  
   //tonumber将字符串转换为数字类型
4.  
   //redis.call('get',key)获取当前库存量
5.  
   //redis.call('decrby',key,qty)扣减所需的库存量
6.  
   //求量小于库存量时扣减成功返回-1,需求量大于库存量时返回所剩库存量
7.  
   //最后将lua语言转成字符串
8.  
   private static String lua ;
9.  
   static {
10.  
    StringBuilder sb = new StringBuilder();
11.  
    sb.append(" local key = KEYS[1] ");
12.  
    sb.append(" local qty = ARGV[1] ");
13.  
    sb.append(" local redis_qty = redis.call('get',key) ");
14.  
    sb.append(" if tonumber(redis_qty) >= tonumber(qty) ");
15.  
    sb.append(" then ");
16.  
    sb.append(" redis.call('decrby',key,qty) ");
17.  
    sb.append(" return -1 ");
18.  
    sb.append(" else ");
19.  
    sb.append(" return tonumber(redis_qty) ");
20.  
    sb.append(" end ");
21.  
    lua = sb.toString();
22.  
    }

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