java实现分布式锁

分布式锁：满足分布式系统或集群模式下多进程可见并且互斥的锁。

跨机器进程间数据同步问题

我们用第三种 悲观锁

加入依赖

        <!-- redis分布式锁 -->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>lock4j-redisson-spring-boot-starter</artifactId>
            <version>2.2.2</version>
        </dependency>

核心代码

package com.study.task;

import com.baomidou.lock.LockInfo;
import com.baomidou.lock.LockTemplate;
import com.baomidou.lock.executor.RedissonLockExecutor;
import com.fasterxml.jackson.databind.ObjectMapper;
import lombok.extern.slf4j.Slf4j;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;

import javax.annotation.Resource;
import java.util.UUID;

@Component
@Slf4j
@EnableScheduling
public class ProductTask {

    @Resource
    private LockTemplate lockTemplate;

    @Scheduled(cron = "0/1 0/5 * * * ?")
    public void productTackStart() {
        //get lock
        LockInfo lockInfo = null;
        try {
            String key = UUID.randomUUID() + "";
            log.info("开始加锁------------key:{}", key);
            lockInfo = lockTemplate.lock(key, 5000L, 100L, RedissonLockExecutor.class);
            //对象转json，可以在使用任意一种方法，google/mybatis/alibaba都有封装
            ObjectMapper Obj = new ObjectMapper();
            String jsonStr = Obj.writeValueAsString(lockInfo);
            log.info("lockInfo:{}", jsonStr);
            log.info("定时任务开始-------");
            //业务代码入口

        } catch (Exception e) {
            log.error("异常：", e);
        } finally {
            //解锁
            if (null == lockInfo) {
                log.info("--------lockInfo is null");
                return;
            }
            boolean releaseLock = lockTemplate.releaseLock(lockInfo);
            log.info("-----releaseLock:{}", releaseLock);
        }
    }
}

简化版

//get lock
            LockInfo lockInfo = null;
            try {
                lockInfo = this.lockTemplate.lock(BRAND_KEY_LOCK, 5000L, 0L,
                        RedissonLockExecutor.class);#BRAND_KEY_LOCK定义为唯一的key
                //业务
                Integer updateBrand = this.updateBrand(brandPageReq, now, mchBrand);
                log.info("updateBrand:{}", updateBrand);
            } catch (Exception e) {
                log.error("修改品牌：", e);
            } finally {
                this.lockTemplate.releaseLock(lockInfo);
            }