package com.seckill.lock;
import com.seckill.redis.RedisClient;
import com.seckill.redis.RedisFactory;
import java.util.Random;
/**
* Created by wuy on 17-2-15.
*/
public class RedisLock {
//纳秒和毫秒之间的转换率
public static final long MILLI_NANO_TIME = 1000 * 1000L;
public static final String LOCKED = "TRUE";
public static final Random RANDOM = new Random();
private String key;
//封装的操作redis的工具
private RedisClient redisClient;
private boolean lock = true;
/**
*
* @param purpose 锁前缀
* @param key 锁定的ID等东西
* @param client
*/
public RedisLock(String purpose, String key){
this.key = purpose + "_" + key + "_lock";
this.redisClient = RedisFactory.getDefaultClient();
}
public RedisLock(String purpose, String key,RedisClient client){
this.key = purpose + "_" + key + "_lock";
this.redisClient = RedisFactory.getDefaultClient();
this.redisClient = client;
}
/**
* 加锁
* 使用方式为：
* lock();
* try{
* executeMethod();
* }finally{
* unlock();
* }
* @param timeout timeout的时间范围内轮询锁
* @param expire 设置锁超时时间
* @return 成功 or 失败
*/
public boolean lock(long timeout,int expire){
long nanoTime = System.nanoTime();
timeout *= MILLI_NANO_TIME;
try {
//在timeout的时间范围内不断轮询锁
while (System.nanoTime() - nanoTime < timeout) {
//锁不存在的话，设置锁并设置锁过期时间，即加锁
if (this.redisClient.setnx(this.key, LOCKED) == 1) {
this.redisClient.expire(key, expire);//设置锁过期时间是为了在没有释放
//锁的情况下锁过期后消失，不会造成永久阻塞
this.lock = true;
return this.lock;
}
System.out.println("出现锁等待");
//短暂休眠，避免可能的活锁
Thread.sleep(3, RANDOM.nextInt(30));
}
} catch (Exception e) {
throw new RuntimeException("locking error",e);
}
return false;
}
public void unlock() {
try {
if(this.lock){
redisClient.delKey(key);//直接删除
}
} catch (Throwable e) {
}
}
}
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