上篇《SpringBoot 集成 redis 分布式锁优化》对死锁的问题进行了优化，今天介绍的是 redis 官方推荐使用的 Redisson ，Redisson 架设在 redis 基础上的 Java 驻内存数据网格（In-Memory Data Grid），基于NIO的 Netty 框架上，利用了 redis 键值数据库。功能非常强大，解决了很多分布式架构中的问题。

Github的wiki地址：https://github.com/redisson/redisson/wiki

官方文档：https://github.com/redisson/redisson/wiki/目录

项目代码结构图：

导入依赖

<dependency>
	<groupId>org.redisson</groupId>
	<artifactId>redisson</artifactId>
	<version>3.8.0</version>
</dependency>

属性配置

在application.properites资源文件中添加单机&哨兵相关配置

server.port=3000

# redisson lock 单机模式
redisson.address=redis://127.0.0.1:6379
redisson.password=

#哨兵模式
#redisson.master-name= master
#redisson.password=
#redisson.sentinel-addresses=10.47.91.83:26379,10.47.91.83:26380,10.47.91.83:26381

注意：

这里如果不加 redis:// 前缀会报 URI 构建错误

Caused by: java.net.URISyntaxException: Illegal character in scheme name at index 0

更多的配置信息可以去官网查看

定义Lock的接口定义类

package com.tuhu.thirdsample.service;

import org.redisson.api.RLock;
import java.util.concurrent.TimeUnit;
/**
 * @author chendesheng
 * @create 2019/10/12 10:48
 */
public interface DistributedLocker {

    RLock lock(String lockKey);

    RLock lock(String lockKey, int timeout);

    RLock lock(String lockKey, TimeUnit unit, int timeout);

    boolean tryLock(String lockKey, TimeUnit unit, int waitTime, int leaseTime);

    void unlock(String lockKey);

    void unlock(RLock lock);
}

Lock接口实现类

package com.tuhu.thirdsample.service;

import org.redisson.api.RLock;
import org.redisson.api.RedissonClient;

import java.util.concurrent.TimeUnit;

/**
 * @author chendesheng
 * @create 2019/10/12 10:49
 */
public class RedissonDistributedLocker implements DistributedLocker{

    private RedissonClient redissonClient;

    @Override
    public RLock lock(String lockKey) {
        RLock lock = redissonClient.getLock(lockKey);
        lock.lock();
        return lock;
    }

    @Override
    public RLock lock(String lockKey, int leaseTime) {
        RLock lock = redissonClient.getLock(lockKey);
        lock.lock(leaseTime, TimeUnit.SECONDS);
        return lock;
    }

    @Override
    public RLock lock(String lockKey, TimeUnit unit ,int timeout) {
        RLock lock = redissonClient.getLock(lockKey);
        lock.lock(timeout, unit);
        return lock;
    }

    @Override
    public boolean tryLock(String lockKey, TimeUnit unit, int waitTime, int leaseTime) {
        RLock lock = redissonClient.getLock(lockKey);
        try {
            return lock.tryLock(waitTime, leaseTime, unit);
        } catch (InterruptedException e) {
            return false;
        }
    }

    @Override
    public void unlock(String lockKey) {
        RLock lock = redissonClient.getLock(lockKey);
        lock.unlock();
    }

    @Override
    public void unlock(RLock lock) {
        lock.unlock();
    }

    public void setRedissonClient(RedissonClient redissonClient) {
        this.redissonClient = redissonClient;
    }
}

redisson属性装配类

package com.tuhu.thirdsample.common;

import lombok.Data;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Configuration;

/**
 * @author chendesheng
 * @create 2019/10/11 20:04
 */
@Configuration
@ConfigurationProperties(prefix = "redisson")
@ConditionalOnProperty("redisson.password")
@Data
public class RedissonProperties {


    private int timeout = 3000;

    private String address;

    private String password;

    private int database = 0;

    private int connectionPoolSize = 64;

    private int connectionMinimumIdleSize=10;

    private int slaveConnectionPoolSize = 250;

    private int masterConnectionPoolSize = 250;

    private String[] sentinelAddresses;

    private String masterName;

}

SpringBoot自动装配类

package com.tuhu.thirdsample.configuration;

import com.tuhu.thirdsample.common.RedissonProperties;
import com.tuhu.thirdsample.service.DistributedLocker;
import com.tuhu.thirdsample.service.RedissonDistributedLocker;

import com.tuhu.thirdsample.util.RedissonLockUtil;
import org.apache.commons.lang3.StringUtils;
import org.redisson.Redisson;
import org.redisson.api.RedissonClient;
import org.redisson.config.Config;
import org.redisson.config.SentinelServersConfig;
import org.redisson.config.SingleServerConfig;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;


/**
 * @author chendesheng
 * @create 2019/10/12 10:50
 */
@Configuration
@ConditionalOnClass(Config.class)
@EnableConfigurationProperties(RedissonProperties.class)
public class RedissonAutoConfiguration {

    @Autowired
    private RedissonProperties redissonProperties;

    /**
     * 哨兵模式自动装配
     * @return
     */
    @Bean
    @ConditionalOnProperty(name="redisson.master-name")
    RedissonClient redissonSentinel() {
        Config config = new Config();
        SentinelServersConfig serverConfig = config.useSentinelServers().addSentinelAddress(redissonProperties.getSentinelAddresses())
                .setMasterName(redissonProperties.getMasterName())
                .setTimeout(redissonProperties.getTimeout())
                .setMasterConnectionPoolSize(redissonProperties.getMasterConnectionPoolSize())
                .setSlaveConnectionPoolSize(redissonProperties.getSlaveConnectionPoolSize());

        if(StringUtils.isNotBlank(redissonProperties.getPassword())) {
            serverConfig.setPassword(redissonProperties.getPassword());
        }
        return Redisson.create(config);
    }

    /**
     * 单机模式自动装配
     * @return
     */
    @Bean
    @ConditionalOnProperty(name="redisson.address")
    RedissonClient redissonSingle() {
        Config config = new Config();
        SingleServerConfig serverConfig = config.useSingleServer()
                .setAddress(redissonProperties.getAddress())
                .setTimeout(redissonProperties.getTimeout())
                .setConnectionPoolSize(redissonProperties.getConnectionPoolSize())
                .setConnectionMinimumIdleSize(redissonProperties.getConnectionMinimumIdleSize());

        if(StringUtils.isNotBlank(redissonProperties.getPassword())) {
            serverConfig.setPassword(redissonProperties.getPassword());
        }

        return Redisson.create(config);
    }

    /**
     * 装配locker类，并将实例注入到RedissLockUtil中
     * @return
     */
    @Bean
    DistributedLocker distributedLocker(RedissonClient redissonClient) {
        DistributedLocker locker = new RedissonDistributedLocker();
        ((RedissonDistributedLocker) locker).setRedissonClient(redissonClient);
        RedissonLockUtil.setLocker(locker);
        return locker;
    }
}

Lock帮助类

package com.tuhu.thirdsample.util;

import com.tuhu.thirdsample.service.DistributedLocker;
import org.redisson.api.RLock;

import java.util.concurrent.TimeUnit;

/**
 * @author chendesheng
 * @create 2019/10/12 10:54
 */
public class RedissonLockUtil {

    private static DistributedLocker redissLock;

    public static void setLocker(DistributedLocker locker) {
        redissLock = locker;
    }

    /**
     * 加锁
     * @param lockKey
     * @return
     */
    public static RLock lock(String lockKey) {
        return redissLock.lock(lockKey);
    }

    /**
     * 释放锁
     * @param lockKey
     */
    public static void unlock(String lockKey) {
        redissLock.unlock(lockKey);
    }

    /**
     * 释放锁
     * @param lock
     */
    public static void unlock(RLock lock) {
        redissLock.unlock(lock);
    }

    /**
     * 带超时的锁
     * @param lockKey
     * @param timeout 超时时间   单位：秒
     */
    public static RLock lock(String lockKey, int timeout) {
        return redissLock.lock(lockKey, timeout);
    }

    /**
     * 带超时的锁
     * @param lockKey
     * @param unit 时间单位
     * @param timeout 超时时间
     */
    public static RLock lock(String lockKey, TimeUnit unit , int timeout) {
        return redissLock.lock(lockKey, unit, timeout);
    }

    /**
     * 尝试获取锁
     * @param lockKey
     * @param waitTime 最多等待时间
     * @param leaseTime 上锁后自动释放锁时间
     * @return
     */
    public static boolean tryLock(String lockKey, int waitTime, int leaseTime) {
        return redissLock.tryLock(lockKey, TimeUnit.SECONDS, waitTime, leaseTime);
    }

    /**
     * 尝试获取锁
     * @param lockKey
     * @param unit 时间单位
     * @param waitTime 最多等待时间
     * @param leaseTime 上锁后自动释放锁时间
     * @return
     */
    public static boolean tryLock(String lockKey, TimeUnit unit, int waitTime, int leaseTime) {
        return redissLock.tryLock(lockKey, unit, waitTime, leaseTime);
    }
}

控制层

package com.tuhu.thirdsample.task;

import com.tuhu.thirdsample.common.KeyConst;
import lombok.extern.slf4j.Slf4j;

import org.redisson.api.RLock;
import org.redisson.api.RedissonClient;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.concurrent.TimeUnit;
/**
 * @author chendesheng
 * @create 2019/10/12 11:03
 */
@RestController
@RequestMapping("/lock")
@Slf4j
public class LockController {
    @Autowired
    RedissonClient redissonClient;
    
    @GetMapping("/task")
    public void task(){
        log.info("task start");
        RLock lock = redissonClient.getLock(KeyConst.REDIS_LOCK_KEY);
        boolean getLock = false;

        try {
            if (getLock = lock.tryLock(0,5,TimeUnit.SECONDS)){
                //执行业务逻辑
                System.out.println("拿到锁干活");

            }else {
                log.info("Redisson分布式锁没有获得锁:{},ThreadName:{}",KeyConst.REDIS_LOCK_KEY,Thread.currentThread().getName());
            }

        } catch (InterruptedException e) {
            log.error("Redisson 获取分布式锁异常,异常信息:{}",e);
        }finally {


            if (!getLock){
                return;
            }
            //如果演示的话需要注释该代码;实际应该放开
            //lock.unlock();
            //log.info("Redisson分布式锁释放锁:{},ThreadName :{}", KeyConst.REDIS_LOCK_KEY, Thread.currentThread().getName());
        }
    }

}

RLock 继承自 java.util.concurrent.locks.Lock，可以将其理解为一个重入锁，需要手动加锁和释放锁。

来看它其中的一个方法：tryLock(long waitTime, long leaseTime, TimeUnit unit)

getLock = lock.tryLock(0,5,TimeUnit.SECONDS)

通过 tryLock() 的参数可以看出，在获取该锁时如果被其他线程先拿到锁就会进入等待，等待 waitTime 时间，如果还没用机会获取到锁就放弃，返回 false；若获得了锁，除非是调用 unlock 释放，那么会一直持有锁，直到超过 leaseTime 指定的时间。

以上就是 Redisson 实现分布式锁的核心方法，有人可能要问，那怎么确定拿的是同一把锁，分布式锁在哪？

这就是 Redisson 的强大之处，其底层还是使用的 Redis 来作分布式锁，在我们的RedissonManager中已经指定了 Redis 实例，Redisson 会进行托管，其原理与我们手动实现 Redis 分布式锁类似。

测试

启动项目，在postman中输入url：http://localhost:3000/lock/task

第一次输入结果，我们可以在控制台看到：

在锁过期时间内再次请求，我们可以在控制台看到：

最后

ok， SpringBoot 集成 Redisson实现分布式锁已经写到最后。使用redisson更加体现一切皆对象，我们不需要知道内部如何实现，只需知道如何使用就行。当然仅仅是知道如何使用是远远不够的，熟悉理解底层原理更为重要！