Jedis实现分布式锁

Posted 2020-12-25 bbchao

Jedis pom

<dependency>
    <groupId>redis.clients</groupId>
    <artifactId>jedis</artifactId>
    <version>2.9.0</version>
</dependency>

JedisUtil

import redis.clients.jedis.*;

import java.util.ArrayList;
import java.util.List;

public class RedisUtil {
   // Redis 服务器 IP
   private String address = "127.0.0.1";

   // Redis的端口号
   private int port = 6379;

   // 访问密码
   private String password = "123456";

   // 连接 redis 等待时间
   private int timeOut = 10000;

   // 可用连接实例的最大数目，默认值为8；
   // 如果赋值为-1，则表示不限制；如果pool已经分配了maxActive个jedis实例，则此时pool的状态为exhausted(耗尽)
   private int maxTotal = -1;

   // 控制一个pool最多有多少个状态为idle(空闲的)的jedis实例，默认值也是8
   private int maxIdle = 200;

   // 等待可用连接的最大时间，单位毫秒，默认值为-1，表示永不超时。如果超过等待时间，则直接抛出JedisConnectionException
   private int maxWait = 10000;

   // 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
   private boolean testOnBorrow = true;

   // 连接池
   private JedisPool jedisPool = null;

   // 构造函数
   public RedisUtil() {
       try {
           JedisPoolConfig config = new JedisPoolConfig();
           config.setMaxTotal(maxTotal);
           config.setMaxIdle(maxIdle);
           config.setMaxWaitMillis(maxWait);
           config.setTestOnBorrow(testOnBorrow);
           jedisPool = new JedisPool(config, address, port, timeOut, password);
       } catch(Exception e) {
           e.printStackTrace();
       }
   }

   // 获取 Jedis 实例
   public Jedis getJedis() {
       if (jedisPool != null) {
           return jedisPool.getResource();
       }
       return null;
   }

}

Jedis实现分布式锁

import redis.clients.jedis.Jedis;

import java.util.Collections;

public class RedisTest {
   private static final String LOCK_SUCCESS = "OK";
   private static final String SET_IF_NOT_EXIST = "NX";
   private static final String SET_WITH_EXPIRE_TIME = "PX";

   /**
    * 尝试获取分布式锁
    * @param jedis Redis客户端
    * @param lockKey 锁
    * @param requestId 请求标识
    * @param expireTime 超期时间
    * @return 是否获取成功
    */
   public static boolean tryGetDistributedLock(Jedis jedis, String lockKey, String requestId, int expireTime) {

       String result = jedis.set(lockKey, requestId, SET_IF_NOT_EXIST, SET_WITH_EXPIRE_TIME, expireTime);

       if (LOCK_SUCCESS.equals(result)) {
           return true;
       }
       return false;

   }


   public static boolean tryReleaseLock(Jedis jedis,String lockKey, String requestId) {
       String script = "if redis.call(‘get‘, KEYS[1]) == ARGV[1] then return redis.call(‘del‘, KEYS[1]) else return 0 end";
       Object result = jedis.eval(script, Collections.singletonList(lockKey), Collections.singletonList(requestId));
           if(LOCK_SUCCESS.equals(jedis.del(lockKey)))
               return true;
       return false;
   }

   public static void main(String[] args) {
       System.out.println(tryGetDistributedLock(new RedisUtil().getJedis(),
               new String("mykey"),new String("hhhh"),50));
   }
}

from ruthless and liuyang0