基于传统的单机模式下的并发锁，已远远不能满足当下高并发大负载的情况，当下常用的并发处理如下

1、使用synchronized关键字

2、select for update 乐观锁

3、使用redis实现同步锁

方案一适合单机模式，

方案二虽然满足多节点服务实例但对变更操作的吞吐量有影响

方案三基于redis nosql数据库在效率与横向扩展方面都大大优于前两种方案

redis 单线程在自身设计上一定程度可避免想成不安全再者其效率高于关系型数据库

本次实现锁机制基于redis 的两个指令查询 redis.cn 网站

指令一：SETNX key value

将key设置值为value，如果key不存在，这种情况下等同SET命令。当key存在时，什么也不做。SETNX是”SET if Not eXists”的简写。

返回值

Integer reply, 特定值:

1 如果key被设置了
0 如果key没有被设置

指令二：GETSET key value

自动将key对应到value并且返回原来key对应的value。如果key存在但是对应的value不是字符串，就返回错误。

返回值

bulk-string-reply: 返回之前的旧值，如果之前Key不存在将返回nil。

步骤一， pom文件

        <dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-data-redis</artifactId></dependency><dependency><groupId>org.apache.commons</groupId><artifactId>commons-pool2</artifactId><version>2.6.0</version></dependency>

步骤二，RedisCacheAutoConfiguration

package com.wh.whcloud.df.config;import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.PropertyAccessor;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.wh.whcloud.core.redis.RedisUtil;
import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.autoconfigure.AutoConfigureAfter;
import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.data.redis.serializer.Jackson2JsonRedisSerializer;
import org.springframework.data.redis.serializer.RedisSerializer;
import org.springframework.data.redis.serializer.StringRedisSerializer;/*** Redis缓存配置** @author */
@Slf4j
@Configuration
@AutoConfigureAfter({RedisAutoConfiguration.class})
public class RedisCacheAutoConfiguration {/*** 重新配置一个RedisTemplate** @param factory* @return*/@Beanpublic RedisTemplate redisTemplate(RedisConnectionFactory factory) {RedisTemplate template = new StringRedisTemplate();template.setConnectionFactory(factory);Jackson2JsonRedisSerializer jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer(Object.class);ObjectMapper om = new ObjectMapper();om.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);om.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);jackson2JsonRedisSerializer.setObjectMapper(om);RedisSerializer<String> stringSerializer = new StringRedisSerializer();// key采用String的序列化方式template.setKeySerializer(stringSerializer);// hash的key也采用String的序列化方式template.setHashKeySerializer(stringSerializer);// value序列化方式采用jacksontemplate.setValueSerializer(jackson2JsonRedisSerializer);// hash的value序列化方式采用jacksontemplate.setHashValueSerializer(jackson2JsonRedisSerializer);template.setDefaultSerializer(jackson2JsonRedisSerializer);log.info("RedisTemplate配置 [{}]", template);return template;}@Bean@ConditionalOnMissingBean(RedisUtil.class)@ConditionalOnBean(RedisTemplate.class)public RedisUtil redisUtils(RedisTemplate redisTemplate) {RedisUtil redisUtil =   new RedisUtil(redisTemplate);log.info("RedisUtil [{}]", redisUtil);return redisUtil;}
}

步骤三， RedisLock 加解锁实现

package com.wh.whcloud.util;import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.core.script.DefaultRedisScript;
import org.springframework.data.redis.core.script.RedisScript;
import java.util.Collections;
import java.util.concurrent.TimeUnit;public class RedisLock {private static final Long SUCCESS = 1L;private long timeout = 9999; //获取锁的超时时间/*** 加锁，无阻塞** @param* @param* @return*/public static Boolean tryLock(RedisTemplate redisTemplate, String key, String value, long expireTime) {try {//SET命令返回OK ，则证明获取锁成功Boolean ret = redisTemplate.opsForValue().setIfAbsent(key, value, expireTime, TimeUnit.MILLISECONDS);return ret;} catch (Exception e) {e.printStackTrace();return false;}return false;}/*Long start = System.currentTimeMillis();for(;;){//SET命令返回OK ，则证明获取锁成功Boolean ret = redisTemplate.opsForValue().setIfAbsent(key, value, expireTime, TimeUnit.SECONDS);return ret;//否则循环等待，在timeout时间内仍未获取到锁，则获取失败long end = System.currentTimeMillis() - start;if (end>=timeout) {return false;}}*//*** 解锁** @param* @param* @return*/public static Boolean unlock(RedisTemplate redisTemplate, String key, String value) {try {String script = "if redis.call('get', KEYS[1]) == ARGV[1] then return redis.call('del', KEYS[1]) else return 0 end";RedisScript<String> redisScript = new DefaultRedisScript<>(script, String.class);//redis脚本执行//Object result = redisTemplate.execute(redisScript, Collections.singletonList(key), value))Object result = redisTemplate.delete(Collections.singletonList(key));if (SUCCESS.equals(result)) {return true;}} catch (Exception e) {e.printStackTrace();return false;}return false;}}

注意：

redisTemplate.execute 是redis脚本执行，可能报错， 具体参考： https://blog.csdn.net/cevery/article/details/108303919

测试：我这里自己创建两个线程测试

@Slf4j
@Component
public class Schedule {@Resourceprivate RedisTemplate redisTemplate;@Scheduled(cron = "0 0/1 * * * ? ")public void getDeviceStatus() throws InterruptedException {//启动两个线程，测试哪一个能够悠闲抢到Redis锁Test1Runnable test1 = new Test1Runnable();new Thread(test1).start();Test2Runnable test2 = new Test2Runnable();new Thread(test2).start();}//自定义个唯一的Key值public String key = "ZX123456789";//保存数据方法public boolean testSave(){//获取锁boolean isOK = RedisLock.tryLock(redisTemplate, key, "key+1", 2000);//处理业务 ，然后释放锁if(isOK){System.out.println("处理完业务，释放锁==="+RedisLock.unlock(redisTemplate, key, "key+1"));}return isOK;}class Test1Runnable implements Runnable {@Overridepublic void run() {boolean result = testSave();log.info(Thread.currentThread().getName()+"Test1获取锁："+result);}}class Test2Runnable implements Runnable {@Overridepublic void run() {boolean result = testSave();log.info(Thread.currentThread().getName()+"Test2获取锁："+result);}}
}

效果：