基于Redis的Setnx实现分布式锁

一、 redis分布式锁原理

 

  并发 到Redis里变成了串行排队，单线程

 

二、基于Redis的Setnx实现分布式锁 

  1、pom

   

  <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>

2、application.properties  配置redis

  

spring.redis.host=192.168.73.130

3、Controller层测试

 

package com.example.distributelock.controller;

import com.example.distributelock.lock.RedisLock;
import com.example.distributelock.lock.ZkLock;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@Slf4j
public class RedisLockController {
    @Autowired
    private RedisTemplate redisTemplate;

    @RequestMapping("redisLock")
    public String redisLock(){
        log.info("我进入了方法！");
        try (RedisLock redisLock = new RedisLock(redisTemplate,"redisKey",30)){
            if (redisLock.getLock()) {
                log.info("我进入了锁！！");
                Thread.sleep(15000);
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
        log.info("方法执行完成");
        return "方法执行完成";
    }

    @RequestMapping("zkLock")
    public String zkLock(){
        log.info("我进入了方法！");
        try (ZkLock zkLock = new ZkLock("localhost:2181","order")){
            if (zkLock.getLock()) {
                log.info("我进入了锁！！");
                Thread.sleep(15000);
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
        log.info("方法执行完成");
        return "方法执行完成";
    }
}

4、Redis的Setnx实现分布式锁操作

package com.example.distributelock.lock;

import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.connection.RedisStringCommands;
import org.springframework.data.redis.core.RedisCallback;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.core.script.RedisScript;
import org.springframework.data.redis.core.types.Expiration;

import java.util.Arrays;
import java.util.List;
import java.util.UUID;

@Slf4j
public class RedisLock implements AutoCloseable {

    private RedisTemplate redisTemplate;
    private String key;
    private String value;
    //单位：秒
    private int expireTime;

    public RedisLock(RedisTemplate redisTemplate,String key,int expireTime){
        this.redisTemplate = redisTemplate;
        this.key = key;
        this.expireTime=expireTime;
        this.value = UUID.randomUUID().toString();
    }

    /**
     * 获取分布式锁
     * @return
     */
    public boolean getLock(){
        RedisCallback<Boolean> redisCallback = connection -> {
            //设置NX
            RedisStringCommands.SetOption setOption = RedisStringCommands.SetOption.ifAbsent();
            //设置过期时间
            Expiration expiration = Expiration.seconds(expireTime);
            //序列化key
            byte[] redisKey = redisTemplate.getKeySerializer().serialize(key);
            //序列化value
            byte[] redisValue = redisTemplate.getValueSerializer().serialize(value);
            //执行setnx操作
            Boolean result = connection.set(redisKey, redisValue, expiration, setOption);
            return result;
        };

        //获取分布式锁
        Boolean lock = (Boolean)redisTemplate.execute(redisCallback);
        return lock;
    }

    public boolean unLock() {
        String script = "if redis.call(\"get\",KEYS[1]) == ARGV[1] then\n" +
                "    return redis.call(\"del\",KEYS[1])\n" +
                "else\n" +
                "    return 0\n" +
                "end";
        RedisScript<Boolean> redisScript = RedisScript.of(script,Boolean.class);
        List<String> keys = Arrays.asList(key);

        Boolean result = (Boolean)redisTemplate.execute(redisScript, keys, value);
        log.info("释放锁的结果："+result);
        return result;
    }


    @Override
    public void close() throws Exception {
        unLock();
    }
}