MySQL分布式鎖是一種用于在分布式系統(tǒng)間協(xié)調(diào)訪問共享資源的技術(shù)。在多個系統(tǒng)中同時訪問一個資源時，容易出現(xiàn)"腦裂"現(xiàn)象，進而導(dǎo)致數(shù)據(jù)一致性問題。因此，使用MySQL分布式鎖可以有效地避免這種問題的出現(xiàn)。

下面是MySQL分布式鎖的使用示例：

CREATE TABLE `distributed_lock` (
`lock_id` varchar(64) NOT NULL COMMENT '鎖ID',
`lock_holder` varchar(64) NOT NULL COMMENT '持有者',
`lock_time` bigint(20) NOT NULL COMMENT '加鎖時間',
PRIMARY KEY (`lock_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
/**
 * 獲取分布式鎖
 *
 * @param lockId       鎖ID
 * @param lockHolder   鎖持有者
 * @param lockTimeout  鎖的過期時間
 * @return true獲取成功，false獲取失敗
 */
public boolean tryGetDistributedLock(String lockId, String lockHolder, long lockTimeout) {
long now = System.currentTimeMillis();
try (Connection conn = dataSource.getConnection();
PreparedStatement ps = conn.prepareStatement(
"INSERT INTO distributed_lock (lock_id, lock_holder, lock_time) " +
"VALUES (?, ?, ?) " +
"ON DUPLICATE KEY UPDATE lock_id = lock_id")) {
while (true) {
// 設(shè)置鎖的過期時間
long lockExpireTime = now + lockTimeout + 1;
ps.setString(1, lockId);
ps.setString(2, lockHolder);
ps.setLong(3, lockExpireTime);
// 嘗試獲取鎖
int affectedRows = ps.executeUpdate();
if (affectedRows == 1) {
return true;
}
// 檢查鎖是否過期，如果過期則修改鎖的持有者
try (PreparedStatement selectStmt = conn.prepareStatement(
"SELECT lock_time FROM distributed_lock WHERE lock_id = ?")) {
selectStmt.setString(1, lockId);
try (ResultSet rs = selectStmt.executeQuery()) {
if (rs.next()) {
long lockTime = rs.getLong(1);
if (lockTime< now) {
try (PreparedStatement updateStmt = conn.prepareStatement(
"UPDATE distributed_lock SET lock_holder = ?, lock_time = ? WHERE lock_id = ?")) {
updateStmt.setString(1, lockHolder);
updateStmt.setLong(2, lockExpireTime);
updateStmt.setString(3, lockId);
affectedRows = updateStmt.executeUpdate();
if (affectedRows == 1) {
return true;
}
}
}
}
}
}
// 等待一段時間后再嘗試獲取鎖
Thread.sleep(10 + (int)(Math.random() * 100));
}
} catch (Exception e) {
e.printStackTrace();
return false;
}
}
/**
 * 釋放分布式鎖
 *
 * @param lockId       鎖ID
 * @param lockHolder   鎖持有者
 * @return true釋放成功，false釋放失敗
 */
public boolean releaseDistributedLock(String lockId, String lockHolder) {
try (Connection conn = dataSource.getConnection();
PreparedStatement ps = conn.prepareStatement(
"DELETE FROM distributed_lock WHERE lock_id = ? AND lock_holder = ?")) {
ps.setString(1, lockId);
ps.setString(2, lockHolder);
int affectedRows = ps.executeUpdate();
return (affectedRows == 1);
} catch (Exception e) {
e.printStackTrace();
return false;
}
}