使用redis来实现分布式锁
public>private static final Logger LOG = LoggerFactory.getLogger(RedisDisLock.class);private transient Thread exclusiveOwnerThread; String lockKey=""; AtomicInteger waitToLock
=new AtomicInteger(0);public RedisDisLock(String lockKey){this.lockKey=CommonType.REDISKEY+lockKey; }
public boolean tryLock(Jedis jedis) { Thread thread
= Thread.currentThread();if(thread==this.getExclusiveOwnerThread()){return true; }
Long i
= jedis.setnx(lockKey, System.currentTimeMillis()+"");if(i.intValue()==1){ jedis.expire(lockKey, CommonType.LOCKEXPIRETIME);
setExclusiveOwnerThread(thread);
return true; }
else{//对于可能性非常低的死锁情况进行解锁 String initTime = jedis.get(lockKey);
if(initTime==null){
LOG.debug("initTime's value is null");
return false;
}
long iniTime=0L;
try{
iniTime = Long.parseLong(initTime);
}
catch(NumberFormatException nfex){
LOG.warn(nfex.getMessage());
jedis.expire(lockKey, 1);
return false;
}
if(((System.currentTimeMillis()-iniTime)/1000-CommonType.LOCKEXPIRETIME-1)>0){
String oldTime = jedis.getSet(lockKey, System.currentTimeMillis()+"");//对于及其极端的情况，lock被线程1处理掉了，但是又被线程2getset新的值了，通过下一次调用trylock()方法处理
if(oldTime==null){
LOG.info("oldTime is null");
return false;
}
if(initTime.equals(oldTime)){
release(jedis);
}
}
}
return false;
}
public boolean tryLock(long timeout, TimeUnit unit,Jedis jedis) throws InterruptedException {
long nanosTimeout = unit.toNanos(timeout);
long lastTime = System.nanoTime();
if(tryLock(jedis)){
return true;
}
try{
int waitLockers = waitToLock.getAndIncrement();
if(waitLockers>=CommonType.WAITLOCKERS){
LOG.debug("wait the lock' thread num is much,so return flase");
return false;
}
for(;;){
if(tryLock(jedis)){
return true;
}
if (nanosTimeout <= 0){
LOG.debug("getlock timeout");
return false;
}
if(nanosTimeout>100000){
LockSupport.parkNanos(100000);//中断100毫秒
}
long now = System.nanoTime();
nanosTimeout -= now - lastTime;
lastTime = now;
if (nanosTimeout <= 0){
LOG.debug("getlock timeout");
return false;
}
if (Thread.interrupted()){
throw new InterruptedException();
}
}
}
finally{
waitToLock.decrementAndGet();
}
}
public void unlock(Jedis jedis) {
Thread thread = Thread.currentThread();
if(thread==this.getExclusiveOwnerThread()){
LOG.debug("unlock the thread {}",thread.getId());
release(jedis);
}
}
private void> setExclusiveOwnerThread(null);
jedis.del(lockKey);
}
/**
* Sets the thread that currently owns exclusive access. A
* <tt>null</tt> argument indicates that no thread owns access.
* This method does not otherwise impose any synchronization or
* <tt>volatile</tt> field accesses.
*/
protected final void setExclusiveOwnerThread(Thread t) {
exclusiveOwnerThread = t;
}
/**
* Returns the thread last set by
* <tt>setExclusiveOwnerThread</tt>, or <tt>null</tt> if never
* set.This method does not otherwise impose any synchronization
* or <tt>volatile</tt> field accesses.
* @return the owner thread
*/
protected final Thread getExclusiveOwnerThread() {
return exclusiveOwnerThread;
}
}
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