java主方法如何处理分布式锁超时

在Java中，处理分布式锁超时主要依赖于所使用的分布式锁实现。这里以Redis和Zookeeper为例，介绍如何处理分布式锁超时。

1. Redis分布式锁超时处理：

使用Redis实现分布式锁时，可以通过设置键的过期时间来实现超时控制。以下是一个简单的示例：

import redis.clients.jedis.Jedis;
import redis.clients.jedis.params.SetParams;

public class RedisLock {
    private Jedis jedis;
    private String lockKey;
    private String lockValue;
    private int expireTime;

    public RedisLock(String redisHost, int redisPort, String lockKey, String lockValue, int expireTime) {
        this.jedis = new Jedis(redisHost, redisPort);
        this.lockKey = lockKey;
        this.lockValue = lockValue;
        this.expireTime = expireTime;
    }

    public boolean tryLock() {
        SetParams params = SetParams.setParams().nx().ex(expireTime);
        String result = jedis.set(lockKey, lockValue, params);
        return "OK".equals(result);
    }

    public void unlock() {
        if (lockValue.equals(jedis.get(lockKey))) {
            jedis.del(lockKey);
        }
    }
}

在这个示例中，我们使用tryLock()方法尝试获取锁，如果成功返回true，否则返回false。unlock()方法用于释放锁。

当使用Redis分布式锁时，可以在业务代码中使用try-catch-finally块来处理超时情况。例如：

public void someMethod() {
    RedisLock redisLock = new RedisLock("localhost", 6379, "myLock", "myValue", 10);
    try {
        if (redisLock.tryLock()) {
            // 执行业务逻辑
        } else {
            // 处理锁超时情况
        }
    } catch (InterruptedException e) {
        // 处理中断异常
    } finally {
        redisLock.unlock();
    }
}

2. Zookeeper分布式锁超时处理：

使用Zookeeper实现分布式锁时，可以通过设置节点的会话超时时间来控制锁的超时。以下是一个简单的示例：

import org.apache.zookeeper.*;
import org.apache.zookeeper.data.Stat;

import java.io.IOException;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.CountDownLatch;

public class ZookeeperLock {
    private ZooKeeper zooKeeper;
    private String lockPath;
    private String lockValue;
    private CountDownLatch latch;

    public ZookeeperLock(String zookeeperConnect, int sessionTimeout, String lockPath, String lockValue) throws IOException, InterruptedException, KeeperException {
        this.zooKeeper = new ZooKeeper(zookeeperConnect, sessionTimeout, event -> {
            // 处理Zookeeper事件
        });
        this.lockPath = lockPath;
        this.lockValue = lockValue;
        this.latch = new CountDownLatch(1);
    }

    public boolean tryLock() throws KeeperException, InterruptedException {
        if (zooKeeper.exists(lockPath, false) == null) {
            zooKeeper.create(lockPath, lockValue.getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
            return true;
        }

        while (true) {
            List<String> children = zooKeeper.getChildren(lockPath, false);
            Collections.sort(children);
            String smallestChild = children.get(0);

            if (lockValue.equals(new String(zooKeeper.getData(lockPath + "/" + smallestChild, false, null)))) {
                if (zooKeeper.exists(lockPath + "/" + smallestChild, false) == null) {
                    zooKeeper.delete(lockPath + "/" + smallestChild, -1);
                    return true;
                } else {
                    latch.await();
                }
            } else {
                return false;
            }
        }
    }

    public void unlock() throws KeeperException, InterruptedException {
        Stat stat = zooKeeper.exists(lockPath, false);
        if (stat != null) {
            zooKeeper.delete(lockPath, -1);
        }
        latch.countDown();
    }
}

在这个示例中，我们使用tryLock()方法尝试获取锁，如果成功返回true，否则返回false。unlock()方法用于释放锁。

当使用Zookeeper分布式锁时，可以在业务代码中使用try-catch-finally块来处理超时情况。例如：

public void someMethod() {
    ZookeeperLock zookeeperLock = new ZookeeperLock("localhost:2181", 3000, "/myLock", "myValue");
    try {
        if (zookeeperLock.tryLock()) {
            // 执行业务逻辑
        } else {
            // 处理锁超时情况
        }
    } catch (Exception e) {
        // 处理异常
    } finally {
        zookeeperLock.unlock();
    }
}

总之，处理分布式锁超时的关键在于在业务代码中使用try-catch-finally块，并在finally块中释放锁。具体的实现方式取决于所使用的分布式锁实现。