Java 正确实现 redis 分布式锁

不念不忘少年蓝@ 2022-05-24 06:35 168阅读 0赞

# Java 正确实现 redis 分布式锁 #

*  Java 正确实现 redis 分布式锁
    
     *  1 源起
     *  2 我想要的效果
     *  3 撸起袖子开干
        
         *  3.1 导入 jedis 依赖
         *  3.2 RedisDistributeLock 接口
         *  3.3 DefaultRedisDistributeLock
         *  3.4 RedisTool
     *  4 必须有测试啊！！！
        
         *  4.1 测试代码
         *  4.2 输出
         *  4.3 优化策略
     *  5 整合到业务中

## 1 源起 ##

> 因为项目中有需要一个需求 ，就是在分布式的环境下 ，要根据一个 key，去获取一把分布式锁。所以。。。。。

## 2 我想要的效果 ##

> 我想要的其实很简单， 就是根据一个 key 获取一个 分布式锁就行了 比如这样

// 获取分布式锁对象
    RedisDistributeLock locker = new DefaultRedisDistributeLock();
    
    // 锁定
    locker.lock(jedis, "test1");
    
    // TODO 业务逻辑
    
    // 解锁
    locker.release(jedis, "test1");

## 3 撸起袖子开干 ##

### 3.1 导入 jedis 依赖 ###

<dependency>
        <groupId>redis.clients</groupId>
        <artifactId>jedis</artifactId>
        <version>2.9.0</version>
    </dependency>

### 3.2 RedisDistributeLock 接口 ###

> RedisDistributeLock 定义了一些分布式锁的接口 实现， 本人能力有限，只实现了 非公平锁

--------------------

package org.study.distributed_look.redis.way2;
    
    import redis.clients.jedis.Jedis;
    
    /** * @Author: huangwenjun * @Description: * @Date: Created in 13:45 2018/5/22 **/
    public interface RedisDistributeLock { 
    
        /** * 公平锁， 只能说 本机的公平 * @param jedis * @param key * @param uuid */
        void fairLock(Jedis jedis, String key, String uuid);
    
        /** * 非公平锁 * @param jedis * @param key * @param uuid */
        void unfairLock(Jedis jedis, String key, String uuid);
    
        /** * 锁 默认非公平 * @param jedis * @param key * @param uuid */
        void lock(Jedis jedis, String key, String uuid);
    
        /** * 解锁 * @param jedis * @param key * @param uuid */
        void release(Jedis jedis, String key, String uuid);
    }

### 3.3 DefaultRedisDistributeLock ###

> DefaultRedisDistributeLock 是我封装的 默认的分布式锁的实现

--------------------

package org.study.distributed_look.redis.way2;
    
    import org.study.distributed_look.redis.RedisTool;
    import redis.clients.jedis.Jedis;
    
    /** * @Author: huangwenjun * @Description: * @Date: Created in 13:48 2018/5/22 **/
    public class DefaultRedisDistributeLock implements RedisDistributeLock { 
    
        /** * 默认 非公平锁 */
        private static final Boolean DEFALUT_FAIR = false;
    
        /** * 过期时间 默认 10 秒, 太短会导致锁不住， 如果业务无法在指定过期时间内 完成， 则必须加长过期时间 */
        private static final Integer DEFAULT_EXPIRE_TIME = 10000;
    
        private Boolean isFair;
    
        private Integer expireTime;
    
        public DefaultRedisDistributeLock() {
            isFair = DEFALUT_FAIR;
            expireTime = DEFAULT_EXPIRE_TIME;
        }
    
        public DefaultRedisDistributeLock(boolean isFair, Integer expireTime) {
            isFair = isFair;
            expireTime = expireTime;
        }
    
        @Override
        public void lock(Jedis jedis, String key, String uuid) {
            if (isFair) {
                fairLock(jedis, key, uuid);
            } else {
                unfairLock(jedis, key, uuid);
            }
        }
    
        @Override
        public void fairLock(Jedis jedis, String key, String uuid) {
            // 通过一个队列维护， 参照 AQS 实现
        }
    
        @Override
        public void release(Jedis jedis, String key, String uuid) {
            try {
                while (true) {
                    boolean released = RedisTool.releaseDistributedLock(jedis, key, uuid);
    
                    if (released) {
                        break;
                    }
                }
            } finally {
                jedis.close();
            }
        }
    
        @Override
        public void unfairLock(Jedis jedis, String key, String uuid) {
            while (true) {
                boolean locked = RedisTool.tryGetDistributedLock(jedis, key, uuid, expireTime);
    
                if (locked) {
                    break;
                }
            }
        }
    }

### 3.4 RedisTool ###

> RedisTool 是我参照网上一个大神的代码， 正确的实现了 redis 分布式锁的 获取 和 释放

--------------------

package org.study.distributed_look.redis;
    
    import redis.clients.jedis.Jedis;
    
    import java.util.Collections;
    
    /** * * redis 分布式锁实现 * * @Author: huangwenjun * @Description: * @Date: Created in 15:00 2018/5/21 **/
    public class RedisTool { 
    
        private static final String LOCK_SUCCESS = "OK";
        private static final String SET_IF_NOT_EXIST = "NX";
        private static final String SET_WITH_EXPIRE_TIME = "PX";
    
        private static final Long RELEASE_SUCCESS = 1L;
    
        /** * 尝试获取分布式锁 * * @param jedis Redis客户端 * @param lockKey 锁 * @param requestId 请求标识 * @param expireTime 超期时间 * @return 是否获取成功 */
        public static boolean tryGetDistributedLock(Jedis jedis, String lockKey, String requestId, int expireTime) {
            String result = jedis.set(lockKey, requestId, SET_IF_NOT_EXIST, SET_WITH_EXPIRE_TIME, expireTime);
    
            if (LOCK_SUCCESS.equals(result)) {
                return true;
            }
    
            return false;
        }
    
        /** * 释放分布式锁 * @param jedis Redis客户端 * @param lockKey 锁 * @param requestId 请求标识 * @return 是否释放成功 */
        public static boolean releaseDistributedLock(Jedis jedis, String lockKey, String requestId) {
            String script = "if redis.call('get', KEYS[1]) == ARGV[1] then return redis.call('del', KEYS[1]) else return 0 end";
            Object result = jedis.eval(script, Collections.singletonList(lockKey), Collections.singletonList(requestId));
    
            if (RELEASE_SUCCESS.equals(result)) {
                return true;
            }
    
            return false;
        }
    }

## 4 必须有测试啊！！！ ##

### 4.1 测试代码 ###

--------------------

package org.study.distributed_look.redis.way2;
    
    import redis.clients.jedis.Jedis;
    import redis.clients.jedis.JedisPool;
    
    /** * @Author: huangwenjun * @Description: * @Date: Created in 14:10 2018/5/22 **/
    public class TestRedisDistributeLock { 
    
        public static void main(String[] args) {
            for (int i = 1; i < 10; i ++) {
                new TestLock().start();
            }
        }
    
        static class TestLock extends Thread {
    
            static RedisDistributeLock locker = new DefaultRedisDistributeLock();
    
            JedisPool jedisPool = new JedisPool();
    
            @Override
            public void run() {
                Jedis jedis = jedisPool.getResource();
                locker.lock(jedis, "test1", "qwerqwer");
    
                // TODO 模拟业务
                System.out.println(Thread.currentThread().getName() + " get lock.....");
                try {
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println(Thread.currentThread().getName() + " release lock.....");
    
                locker.release(jedis, "test1", "qwerqwer");
            }
        }
    }

### 4.2 输出 ###

Thread-4 get lock.....
    Thread-4 release lock.....
    Thread-2 get lock.....
    Thread-2 release lock.....
    Thread-7 get lock.....
    Thread-7 release lock.....
    Thread-9 get lock.....
    Thread-9 release lock.....
    Thread-0 get lock.....
    Thread-0 release lock.....
    Thread-8 get lock.....
    Thread-8 release lock.....
    Thread-5 get lock.....
    Thread-5 release lock.....
    Thread-6 get lock.....
    Thread-6 release lock.....
    Thread-3 get lock.....
    Thread-3 release lock.....

### 4.3 优化策略 ###

**一些优化策略**

*  1 这里为了简单起见， 没有优化 jedis 的连接池， 生产环境 必须手动设置 jedis 连接池
 *  2 locker.lock(jedis, “test1”, “qwerqwer”); 第三个 参数可以用 uuid, 至于为什么要有第三个参数 参见

> [https://www.cnblogs.com/linjiqin/p/8003838.html][https_www.cnblogs.com_linjiqin_p_8003838.html]

## 5 整合到业务中 ##

// 获取分布式锁对象
    RedisDistributeLock locker = new DefaultRedisDistributeLock();
    
    // 锁定
    locker.lock(jedis, "test1", "uuid");
    
    // TODO 业务逻辑
    
    // 解锁
    locker.release(jedis, "test1", "uuid");

--------------------

**和之前设想的基本一致, 如果有人发现问题 欢迎指正**

--------------------

*  ref : [https://www.cnblogs.com/linjiqin/p/8003838.html][https_www.cnblogs.com_linjiqin_p_8003838.html]

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[https_www.cnblogs.com_linjiqin_p_8003838.html]: https://www.cnblogs.com/linjiqin/p/8003838.html