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This article mainly explains "how to use Redis as a global lock in SpringBoot". The explanation in this article is simple and clear, and is easy to learn and understand. Please follow the editor's train of thought to study and learn "how to use Redis as a global lock in SpringBoot".

1. Simulate resource competition without lock public class CommonConsumerService {/ / inventory number static int goodsCount = 900; / / sell number static int saleCount = 0; public static void main (String [] args) throws InterruptedException {for (int I = 0; I)

{try {Thread.sleep (2);} catch (InterruptedException e) {} if (goodsCount > 0) {goodsCount--; System.out.println ("surplus inventory:" + goodsCount + "number sold" + saleCount);}}) .start ();} Thread.sleep (3000) }}

After one run, the output of the last few lines is as follows, it is obvious that something went wrong, but only 899 items were sold out of the remaining 0 items, and it is obvious that some items were embezzled by a thread.

...

Surplus inventory: 5 sold 893

Surplus inventory: 5 sold 894

Surplus inventory: 4 sold 895

Surplus inventory: 2 sold 896

Remaining inventory: 2 sold 897

Surplus inventory: 1 number sold 898

Remaining inventory: 0 sold 899

Use redis to add locks

Redis is single-threaded and executed serially, so then use redis to lock the resource.

1. First, introduce dependency.

Compile "org.springframework.boot:spring-boot-starter-data-redis"

two。 Introduction of redis locking tool class

Package com.kingboy.common.utils;import redis.clients.jedis.Jedis;import java.util.Collections;/** * @ author kingboy--KingBoyWorld@163.com * @ date 2017-12-29 1:57 * @ desc Redis tool. * / public class RedisTool {private static final String LOCK_SUCCESS = "OK"; private static final String SET_IF_NOT_EXIST = "NX"; private static final String SET_WITH_EXPIRE_TIME = "PX"; private static final Long RELEASE_SUCCESS = 1L / * attempt to acquire distributed lock * @ param jedis Redis client * @ param lockKey lock * @ param requestId request identification * @ param expireTime timeout * @ return whether to obtain successful * / public static boolean tryGetDistributedLock (Jedis jedis, String lockKey, String requestId, int expireTime) {String result = jedis.set (lockKey, requestId, SET_IF_NOT_EXIST) SET_WITH_EXPIRE_TIME, expireTime) If (LOCK_SUCCESS.equals (result)) {return true;} return false } / * release distributed lock * @ param jedis Redis client * @ param lockKey lock * @ param requestId request identification * @ return whether the release was successful * / public static boolean releaseDistributedLock (Jedis jedis, String lockKey, String requestId) {String script = "if redis.call ('get', KEYS [1]) = ARGV [1] then return redis.call (' del') KEYS [1]) else return 0 end " Object result = jedis.eval (script, Collections.singletonList (lockKey), Collections.singletonList (requestId)); if (RELEASE_SUCCESS.equals (result)) {return true;} return false;}}

3. Adapt the sample code with no locks above as follows:

Public class RedisLockConsumerService {/ / inventory number static int goodsCount = 900; / / number sold static int saleCount = 0; @ SneakyThrows public static void main (String [] args) {JedisPool jedisPool = new JedisPool (new JedisPoolConfig (), "192.168.0.130", 6379, 1000); for (int I = 0; I)

{try {Thread.sleep (2);} catch (InterruptedException e) {} Jedis jedis = jedisPool.getResource (); boolean lock = false; while (! lock) {lock = RedisTool.tryGetDistributedLock (jedis, "goodsCount", Thread.currentThread () .getName (), 10) } if (lock) {if (goodsCount > 0) {goodsCount--; System.out.println ("surplus inventory:" + goodsCount + "number sold" + saleCount) }} RedisTool.releaseDistributedLock (jedis, "goodsCount", Thread.currentThread (). GetName (); jedis.close ();}) .start ();} Thread.sleep (3000); jedisPool.close ();}}

The output of the program executed several times is as follows, and you can see that the results are orderly and correct.

...

Surplus inventory: 6 sold 894

Surplus inventory: 5 sold 895

Surplus inventory: 4 sold 896

Remaining inventory: 3 sold 897

Surplus inventory: 2 sold 898

Remaining inventory: 1 number sold 899

Remaining inventory: 0 sold 900

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