zookeeper实现分布式锁

package dubbotest;import org.slf4j.Logger;  import org.slf4j.LoggerFactory;  import org.apache.zookeeper.*;  import org.apache.zookeeper.data.Stat;  import java.util.List;  import java.io.IOException;  import java.util.Collections;  import java.util.concurrent.CountDownLatch;    public class DistributedLock implements Watcher{      private int threadId;      private ZooKeeper zk = null;      private String selfPath;      private String waitPath;      private String LOG_PREFIX_OF_THREAD;      private static final int SESSION_TIMEOUT = 10000;      private static final String GROUP_PATH = "/disLocks";      private static final String SUB_PATH = "/disLocks/sub";      private static final String CONNECTION_STRING = "192.168.110.154:2181";            private static final int THREAD_NUM = 10;       //确保连接zk成功；      private CountDownLatch connectedSemaphore = new CountDownLatch(1);      //确保所有线程运行结束；      private static final CountDownLatch threadSemaphore = new CountDownLatch(THREAD_NUM);      private static final Logger LOG = LoggerFactory.getLogger(DistributedLock.class);      public DistributedLock(int id) {          this.threadId = id;          LOG_PREFIX_OF_THREAD = "【第"+threadId+"个线程】";      }      public static void main(String[] args) {          for(int i=0; i < THREAD_NUM; i++){              final int threadId = i+1;              new Thread(){                  @Override                  public void run() {                      try{                          DistributedLock dc = new DistributedLock(threadId);                          dc.createConnection(CONNECTION_STRING, SESSION_TIMEOUT);                          //GROUP_PATH不存在的话，由一个线程创建即可；                          synchronized (threadSemaphore){                              dc.createPath(GROUP_PATH, "该节点由线程" + threadId + "创建", true);                          }                          dc.getLock();                      } catch (Exception e){                          LOG.error("【第"+threadId+"个线程】 抛出的异常：");                          e.printStackTrace();                      }                  }              }.start();          }          try {              threadSemaphore.await();              LOG.info("所有线程运行结束!");          } catch (InterruptedException e) {              e.printStackTrace();          }      }      /**      * 获取锁      * @return      */      private void getLock() throws KeeperException, InterruptedException {          selfPath = zk.create(SUB_PATH,null, ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);          LOG.info(LOG_PREFIX_OF_THREAD+"创建锁路径:"+selfPath);          if(checkMinPath()){              getLockSuccess();          }      }      /**      * 创建节点      * @param path 节点path      * @param data 初始数据内容      * @return      */      public boolean createPath( String path, String data, boolean needWatch) throws KeeperException, InterruptedException {          if(zk.exists(path, needWatch)==null){              LOG.info( LOG_PREFIX_OF_THREAD + "节点创建成功, Path: "                      + this.zk.create( path,                      data.getBytes(),                      ZooDefs.Ids.OPEN_ACL_UNSAFE,                      CreateMode.PERSISTENT )                      + ", content: " + data );          }          return true;      }      /**      * 创建ZK连接      * @param connectString  ZK服务器地址列表      * @param sessionTimeout Session超时时间      */      public void createConnection( String connectString, int sessionTimeout ) throws IOException, InterruptedException {              zk = new ZooKeeper( connectString, sessionTimeout, this);              connectedSemaphore.await();      }      /**      * 获取锁成功     */      public void getLockSuccess() throws KeeperException, InterruptedException {          if(zk.exists(this.selfPath,false) == null){              LOG.error(LOG_PREFIX_OF_THREAD+"本节点已不在了...");              return;          }          LOG.info(LOG_PREFIX_OF_THREAD + "获取锁成功，赶紧干活！");          Thread.sleep(2000);          LOG.info(LOG_PREFIX_OF_THREAD + "删除本节点："+selfPath);          zk.delete(this.selfPath, -1);          releaseConnection();          threadSemaphore.countDown();      }      /**      * 关闭ZK连接      */      public void releaseConnection() {          if ( this.zk !=null ) {              try {                  this.zk.close();              } catch ( InterruptedException e ) {}          }          LOG.info(LOG_PREFIX_OF_THREAD + "释放连接");      }      /**      * 检查自己是不是最小的节点      * @return      */      public boolean checkMinPath() throws KeeperException, InterruptedException {           List<String> subNodes = zk.getChildren(GROUP_PATH, false);           Collections.sort(subNodes);           int index = subNodes.indexOf( selfPath.substring(GROUP_PATH.length()+1));           switch (index){               case -1:{                   LOG.error(LOG_PREFIX_OF_THREAD+"本节点已不在了..."+selfPath);                   return false;               }               case 0:{                   LOG.info(LOG_PREFIX_OF_THREAD+"子节点中，我果然是老大"+selfPath);                   return true;               }               default:{                   this.waitPath = GROUP_PATH +"/"+ subNodes.get(index - 1);                   LOG.info(LOG_PREFIX_OF_THREAD+"获取子节点中，排在我前面的"+waitPath);                   try{                       zk.getData(waitPath, true, new Stat());                       return false;                   }catch(KeeperException e){                       if(zk.exists(waitPath,false) == null){                           LOG.info(LOG_PREFIX_OF_THREAD+"子节点中，排在我前面的"+waitPath+"已失踪，幸福来得太突然?");                           return checkMinPath();                       }else{                           throw e;                       }                   }               }                              }             }      public void process(WatchedEvent event) {          if(event == null){              return;          }          Event.KeeperState keeperState = event.getState();          Event.EventType eventType = event.getType();          if ( Event.KeeperState.SyncConnected == keeperState) {              if ( Event.EventType.None == eventType ) {                  LOG.info( LOG_PREFIX_OF_THREAD + "成功连接上ZK服务器" );                  connectedSemaphore.countDown();              }else if (event.getType() == Event.EventType.NodeDeleted && event.getPath().equals(waitPath)) {                  LOG.info(LOG_PREFIX_OF_THREAD + "收到情报，排我前面的家伙已挂，我是不是可以出山了？");                  try {                      if(checkMinPath()){                          getLockSuccess();                      }                  } catch (KeeperException e) {                      e.printStackTrace();                  } catch (InterruptedException e) {                      e.printStackTrace();                  }              }          }else if ( Event.KeeperState.Disconnected == keeperState ) {              LOG.info( LOG_PREFIX_OF_THREAD + "与ZK服务器断开连接" );          } else if ( Event.KeeperState.AuthFailed == keeperState ) {              LOG.info( LOG_PREFIX_OF_THREAD + "权限检查失败" );          } else if ( Event.KeeperState.Expired == keeperState ) {              LOG.info( LOG_PREFIX_OF_THREAD + "会话失效" );          }      }  }