今天聊聊分布式锁 No.86

<dependency>
    <groupId>redis.clients</groupId>
    <artifactId>jedis</artifactId>
    <version>2.9.0</version>
    <type>jar</type>
    <scope>compile</scope>
</dependency>

package lock;

import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;
import redis.clients.jedis.JedisPoolConfig;
import utils.Printer;

import java.util.Collections;
import java.util.ResourceBundle;

/**
 * @Author  大蕉
 * @Since   2018.02.13
 * @desc    基于redis的分布式锁实现
 */


public class RedisManager {
   public static JedisPool jedisPool;
   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";
   private static final Long RELEASE_SUCCESS = 1L;


   /**
    * 
    * 过期时间设置
    * EX second ：设置键的过期时间为 second 秒。 SET key value EX second 效果等同于 SETEX key second value 。
    * PX millisecond ：设置键的过期时间为 millisecond 毫秒。 SET key value PX millisecond 效果等同于 PSETEX key millisecond value 。
    *
    * 执行条件设置
    * NX ：只在键不存在时，才对键进行设置操作。 SET key value NX 效果等同于 SETNX key value 。
    * XX ：只在键已经存在时，才对键进行设置操作。
    */


   static {

      //读取相关的配置
      ResourceBundle resourceBundle = ResourceBundle.getBundle("redis");
      int maxActive = Integer.parseInt(resourceBundle.getString("redis.pool.maxActive"));
      int maxIdle = Integer.parseInt(resourceBundle.getString("redis.pool.maxIdle"));
      int maxWait = Integer.parseInt(resourceBundle.getString("redis.pool.maxWait"));

      String ip = resourceBundle.getString("redis.ip");
      int port = Integer.parseInt(resourceBundle.getString("redis.port"));

      JedisPoolConfig config = new JedisPoolConfig();
      //设置最大连接数
      config.setMaxTotal(maxActive);
      //设置最大空闲数
      config.setMaxIdle(maxIdle);
      //设置超时时间
      config.setMaxWaitMillis(maxWait);
      //初始化连接池
      jedisPool = new JedisPool(config, ip, port);
   }


   public static boolean tryLock(String key,String value,int expireSecond){
      Jedis jedis = jedisPool.getResource();
      if(jedis == null){
         return false;
      }

      String result = jedis.set(key, value, SET_IF_NOT_EXIST, SET_WITH_EXPIRE_TIME, expireSecond);

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

   }

   public static boolean releaseDistributedLock(String key,String value) {

      Jedis jedis = jedisPool.getResource();
      if(jedis == null){
         return false;
      }

      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(key), Collections.singletonList(value));

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

   }


   public static void main(String[] args){
      Printer.println(tryLock("A","B",100));
      Printer.println(releaseDistributedLock("A","B"));
   }
}