分布式锁简单实现代码

分布式锁可以通过各种方式实现，例如使用数据库、缓存、第三方服务等。以下是一种常见的基于数据库的分布式锁实现方式：

import java.sql.*;

public class DistributedLock {
    // 数据库连接信息
    private static final String DB_URL = "jdbc:mysql://localhost:3306/test";
    private static final String DB_USER = "root";
    private static final String DB_PASSWORD = "password";

    // 锁名称
    private String lockName;

    // 数据库连接
    private Connection connection;

    public DistributedLock(String lockName) {
        this.lockName = lockName;
        try {
            // 初始化数据库连接
            connection = DriverManager.getConnection(DB_URL, DB_USER, DB_PASSWORD);
        } catch (SQLException e) {
            throw new RuntimeException("Failed to initialize database connection.", e);
        }
    }

    // 获取锁
    public boolean acquire() {
        try {
            // 开启事务
            connection.setAutoCommit(false);

            // 尝试在数据库中插入一条记录，记录的名称为锁名称
            PreparedStatement statement = connection.prepareStatement(
                    "INSERT INTO distributed_lock (lock_name) VALUES (?)");
            statement.setString(1, lockName);
            statement.executeUpdate();

            // 提交事务
            connection.commit();
            return true;
        } catch (SQLException e) {
            // 锁已存在，获取锁失败
            return false;
        } finally {
            try {
                // 恢复自动提交
                connection.setAutoCommit(true);
            } catch (SQLException e) {
                throw new RuntimeException("Failed to set auto-commit to true.", e);
            }
        }
    }

    // 释放锁
    public void release() {
        try {
            // 开启事务
            connection.setAutoCommit(false);

            // 删除数据库中锁名称为锁名称的记录
            PreparedStatement statement = connection.prepareStatement(
                    "DELETE FROM distributed_lock WHERE lock_name = ?");
            statement.setString(1, lockName);
            statement.executeUpdate();

            // 提交事务
            connection.commit();
        } catch (SQLException e) {
            throw new RuntimeException("Failed to release lock.", e);
        } finally {
            try {
                // 恢复自动提交
                connection.setAutoCommit(true);
            } catch (SQLException e) {
                throw new RuntimeException("Failed to set auto-commit to true.", e);
            }
        }
    }
}

使用示例：

public class DistributedLockExample {
    public static void main(String[] args) {
        DistributedLock distributedLock = new DistributedLock("mylock");
        try {
            // 尝试获取锁
            if (distributedLock.acquire()) {
                // 获取锁成功，执行业务逻辑
                System.out.println("Acquired lock successfully.");
                // ...
            } else {
                // 获取锁失败，执行其他逻辑
                System.out.println("Failed to acquire lock.");
                // ...
            }
        } finally {
            // 释放锁
            distributedLock.release();
        }
    }
}

以上代码实现了一个简单的基于数据库的分布式锁。在获取锁时，通过在数据库中插入一条记录来进行加锁操作；在释放锁时，通过删除相应的记录来进行解锁操作。