Redis implements distributed locks

redis The distributed lock core of is in setnx Method , Successfully returns 1, Failure to return 0

Case study ： build springboot Integrate redis Implement distributed locks ,100 Scenario where multiple threads produce order numbers at the same time

Ideas ：

1, Get the lock , Successfully executed section 2 Step , If it fails, wait for the lock to be acquired successfully

2, Executive business

3, Release the lock

1,pom file

        <!-- Integrate SpringBoot-->
         <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
            <version>2.6.2</version>
        </dependency>

        <!-- Integrate redis-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-redis</artifactId>
            <version>2.6.3</version>
        </dependency>

2. establish RedisUtil class

package com.hyw.util;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;
import java.time.Duration;
import java.util.concurrent.TimeUnit;

@Component
public class RedisUtil {

    /**
     *  obtain redis Templates 
     */
    @Autowired
    private StringRedisTemplate redis;

    public void setStr(String key, String value){
        setStr(key, value, null);
    }

    /**
     *  Save string 
     * @param key
     * @param value
     * @param timeOut
     */
    public void setStr(String key, String value, Long timeOut){
        redis.opsForValue().set(key, value);
        if(timeOut != null)
            redis.expire(key, timeOut, TimeUnit.SECONDS);
    }

    /**
     * SetNx command   Every time SetNx Check that  key Does it already exist , If it already exists, no operation will be performed . Return to 0  If it doesn't exist, you can add it directly key
     * @param key
     * @param value
     * @param timeOut
     * @return
     */
    public Integer setnx(String key, String value, Long timeOut){
        boolean flag = redis.opsForValue().setIfAbsent(key,value, timeOut, TimeUnit.SECONDS);

        return flag?1:0;
    }

    public Integer setnx(String key, String value){
        return setnx(key, value, null);
    }

    /**
     *  Delete key
     * @param key
     */
    public void del(String key){
        redis.delete(key);
    }

    public String getStr(String key){
        return redis.opsForValue().get(key);
    }
}

3. establish RedisLock class

package com.hyw.lock;

import com.hyw.contans.OrderContans;
import com.hyw.util.RedisUtil;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import java.util.UUID;

@Component
public class RedisLock {
    @Autowired
    private RedisUtil redisUtil;

    public String getLock(String lockKey, int notLockTime){

        // Calculate the time-out for trying to acquire a lock 
        Long endTime = System.currentTimeMillis() + notLockTime;

        // Exit the loop when it times out 
        while (System.currentTimeMillis() < endTime){
            String lockValue = UUID.randomUUID().toString();
            if(redisUtil.setnx(lockKey, lockValue, notLockTime*1l/1000) == OrderContans.lockSuccess){
                System.out.println(Thread.currentThread().getName() +" Lock acquired successfully ！");
                return lockValue;
            }
            try {
                Thread.sleep(10);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        return null;
    }

    /**
     *  Release the lock 
     * @param lockKey
     * @param lockValue
     * @return
     */
    public void unlock(String lockKey, String lockValue){
        // Judge lockValue  Whether the user who has snatched the lock , If yes, delete it , Avoid deleting other people's locks 
        if(lockValue.equals(redisUtil.getStr(lockKey))){
            redisUtil.del(lockKey);
            System.out.println(Thread.currentThread().getName() +" Lock release successful ！");
        }
    }

}

 4, Create constant classes OrderContans

package com.hyw.contans;

public class OrderContans {
    /**
     * 1  Get lock , 0  Lock not acquired 
     */
    public static int lockSuccess = 1;

    /**
     *  Order lock  key
     */
    public static final String LOCK_KEY = "order_lock";


    /**
     *  Set lock timeout  10 second 
     */
    public static int notLockTime = 10000;
}

5,service Cheng Chuang OrderService class , Generate orders

package com.hyw.service;

import com.hyw.contans.OrderContans;
import com.hyw.lock.RedisLock;
import com.hyw.util.OrderUtil;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.util.StringUtils;

@Component
public class OrderService {

    @Autowired
    private RedisLock redisLock;

    public void getOrderNum(){
        //1. Get the lock 
        String lockValue = redisLock.getLock(OrderContans.LOCK_KEY, OrderContans.notLockTime);

        if(StringUtils.isEmpty(lockValue)){
            System.out.println(" Lock acquisition failed ！");
            return;
        }
        System.out.println(" Order number obtained successfully ..."+ OrderUtil.getOrderNumber());


        //3. Release the lock 
        redisLock.unlock(OrderContans.LOCK_KEY, lockValue);
        System.out.println();
    }

}

6, Create a controller layer OrderController, test result

package com.hyw.controller;

import com.hyw.service.OrderService;
import com.hyw.util.RedisUtil;

@RestController
public class OrderController {

    @Autowired
    private RedisUtil redisUtil;
    @Autowired
    private OrderService orderService;
 
    /**
     *  Get the order number 
     * @return
     */
    @RequestMapping("/getOrderNum")
    public String getOrderNum(){
        for (int i = 0; i < 100; i++) {
            new Thread(new Runnable() {
                public void run() {
                    orderService.getOrderNum();
                }
            }).start();
        }

        return "success";
    }
}

7,springboot Start class

package com.hyw;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

import java.text.SimpleDateFormat;
import java.util.Date;

@SpringBootApplication
public class ApplicationMain {
    public static void main(String[] args) {
        SpringApplication.run(ApplicationMain.class, args);
    }
}

Running results ：

http://localhost:8888/getOrderNum