Detailed analysis of the survival time (expire) of redis keys in Java

1. You can use the expire command in redis to set the survival time of a key. After the time is up, redis will automatically delete it
expire Set the survival time (unit/second)
pexpire Set the survival time (unit/millisecond)
ttl/pttl View the remaining survival time of the key
persist Cancel the survival time
expireat [key] unix timestamp 1351858600
pexpireat [key] unix timestamp (milliseconds) 1351858700000
2. Application scenarios
Limited-time promotions
Website data cache (for some data that needs to be updated regularly)
Limit the frequency of website visitor visits (for example: a maximum of 10 visits per minute)

    /** 
         * 限制网站访客访问频率（例如：1分钟最多访问10次）,其中： 访客通过IP标识，即同一个IP在1分钟内仅能访问10次 
         */  
        @Test  
        public void test4(){  
              final String ip = "127.0.0.1" ;  
             Jedis redis = null;  
              //模拟同一个用户连续访问20次  
              for(int i =0;i <20;i ++){  
                  boolean t = validate(ip);  
                  if(t ){  
                     System. out.println("恭喜你，购票成功！" +i );  
                 } else{  
                      //获取当前ip过期时间  
                      redis = getRedis();  
                      break;  
                 }  
             }  
              while(true &&redis.ttl(ip)>0){  
                 System. out.println("抱歉，你访问过度频繁，请" +redis .ttl(ip )+"秒后再来访问！" );  
                  try {  
                     Thread. sleep(1000);  
                 } catch (InterruptedException e ) {  
                      e.printStackTrace();  
                 }  
             }  
             System. out.println("你可以再次访问了" );  
        }  
      
        /** 
         * 
         * @param ip 
         * @return  true: 可以访问，false： 表示已经达到最大上线 
         */  
        public boolean validate( String ip ) {  
             Jedis jedis = getRedis();  
             String value = jedis.get( ip);  
              if(value ==null||value.length()==0){ //第一次访问  
                  jedis.setex( ip, 60,String. valueOf(0));  
             } else{  
                  int v = Integer.parseInt (value );  
                  if(v >=10){  
                      return false ;  
                 }  
             }  
              jedis.incr( ip);  
              return true ;  
        }  
      
        /** 
         * @return 
         */  
        public Jedis getRedis() {  
              jedisPool = getJedisPool();  
             Jedis jedis = jedisPool.getResource();  
              return jedis ;  
        }  
      
        /** 
         * 
         */  
        public JedisPool getJedisPool() {  
             JedisPoolConfig poolConfig = new JedisPoolConfig();  
              // 控制一个pool最多有多少个 jedis实例。  
              poolConfig.setMaxTotal(1000);  
              // 控制一个pool最多有多少个状态为idle(空闲的)的 jedis实例。  
              poolConfig.setMaxIdle(10);  
              // 表示当borrow(引入)一个 jedis实例时，最大的等待时间，如果超过等待时间，则直接抛出JedisConnectionException；  
              poolConfig.setMaxWaitMillis(200000);  
              // 在borrow一个jedis实例时，是否提前进行validate操作；如果为true，则得到的 jedis实例均是可用的；  
              poolConfig.setTestOnBorrow(true);  
      
              return new JedisPool(poolConfig, host, port);  
        }

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