利用redis的transaction功能，实现分布式下加锁

package memcached;import java.util.List;import redis.clients.jedis.Jedis;import redis.clients.jedis.Transaction;public class TestJedisLock {Jedis jedis = new Jedis("127.0.0.1", 6379);public static void main(String[] args) {TestJedisLock t = new TestJedisLock();System.out.println(t.testLock());}public boolean testLock() {String pk = "mypk";String lockPk = "lock" + pk;  String lockValue = String.valueOf(System.currentTimeMillis()) + "111";   try {      if(jedis.exists(lockPk)) { // other one locked already           System.out.println("Already locked pk:" + pk);          return false;      }        jedis.watch(lockPk);// make sure below operation is particle       jedis.multi();            Transaction trans = new Transaction(jedis.getClient());      trans.set(lockPk, lockValue);      trans.expire(lockPk, 60*60);      List<Object> ret = trans.exec();            if(ret == null) {      System.out.println("Concurrent lock fail for pk:" + pk);          return false;      }            String lockedValue = jedis.get(lockPk);            return lockValue.equals(lockedValue); // locked success    } catch (Exception e) {  System.out.println("Exception in lock for pk:" + pk);       return false;  }}}