网站建设经验大总结seo网络推广课程

文章要点

• 自定义配置属性类
• 集成配置RedisTemplate
• 集成配置分布式锁Redisson
• 使用分布式锁简单实现超卖方案

1. 项目结构

2. 集成RedisTemplate和Redisson

添加依赖
依赖的版本与继承的spring-boot-starter-parent工程相对应，可写可不写

<!--spring data redis & cache--><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-data-redis</artifactId></dependency><!-- redis依赖commons-pool 这个依赖一定要添加 --><dependency><groupId>org.apache.commons</groupId><artifactId>commons-pool2</artifactId></dependency><!--redisson--><dependency><groupId>org.redisson</groupId><artifactId>redisson-spring-boot-starter</artifactId><version>3.15.6</version></dependency><!-- https://mvnrepository.com/artifact/org.projectlombok/lombok --><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><scope>provided</scope></dependency>

大概图解

如上图，先配置application.yml设置Redis的各项属性包括ip，端口，密码。再注入。

server:port: 8080# Redis配置
spring:redis:host: 192.168.200.131port: 6379password: root

// RedisConfigProperties.java
@Data
@ConfigurationProperties(prefix = "spring.redis")
public class RedisConfigProperties {private String host;private int port;private String password;
}// RedisTemplateConfig.java
@Configuration
public class RedisTemplateConfig {@AutowiredRedisConfigProperties redisConfigProperties;@Beanpublic RedisConnectionFactory redisConnectionFactory() {RedisStandaloneConfiguration config = new RedisStandaloneConfiguration(redisConfigProperties.getHost(), redisConfigProperties.getPort());config.setPassword(redisConfigProperties.getPassword());return new LettuceConnectionFactory(config);}@Beanpublic RedisTemplate<String, Object> redisTemplate(){RedisTemplate<String,Object> template = new RedisTemplate<>();template.setConnectionFactory(redisConnectionFactory());// 设置序列化器等其他配置return template;}
}// RedissonConfig.java
@Configuration
@EnableConfigurationProperties({RedisConfigProperties.class})
public class RedissonConfig {@AutowiredRedisConfigProperties redisConfigProperties;@Beanpublic RedissonClient redissonClient(){// 1. 创建配置文件Config config = new Config();// 2. 设置单节点服务器配置config.useSingleServer().setAddress("redis://"+redisConfigProperties.getHost()+":"+redisConfigProperties.getPort());// 3. 如果Redis设置了密码，这里需要设置密码config.useSingleServer().setPassword(redisConfigProperties.getPassword());// 4. 创建RedissonClient实例RedissonClient redisson = Redisson.create(config);return redisson;}
}

到这里，RedisTemplate和Redisson就已经集成好了，后续使用只需要注入就行。
例如

@RestController
@RequestMapping(value = "/order")
public class OrderController {@Autowired//private RedisTemplate redisTemplate;private StringRedisTemplate redisTemplate; //通常用这个StringRedisTemplate@Autowiredprivate RedissonClient redissonClient;......
}

3. 模拟分布式场景下超卖现象

OrderController

	/**** 抢单*/@GetMapping(value = "/v1/{id}/{num}")public String addv1(@PathVariable(value = "id")String id,@PathVariable("num")Long num) throws InterruptedException {// 1.查询库存int count = Integer.valueOf(redisTemplate.opsForValue().get(id));System.out.println("剩余库存:"+count);// 2.库存充足if (count>=num){//模拟操作TimeUnit.SECONDS.sleep(5);//递减库存Long decrement = redisTemplate.opsForValue().decrement(id, num);System.out.println("递减库存后剩余库存:"+decrement);//其它操作 略System.out.println("----添加订单了！");return "下单成功";}//库存不足else {return "库存不足";}}

复制一个端口为8081的配置，模拟分布式服务

启动两个服务

在Redis中设置一个键值对water:2，模拟水的库存为2.
浏览器同时发送2个请求，模拟有2个用户同时每人买2瓶水
http://127.0.0.1:8080/order/v1/water/2
http://127.0.0.1:8081/order/v1/water/2

出现超卖现象

4. 利用Redisson分布式锁，防止超卖

关键代码

RLock lock = redissonClient.getLock("mylock_" + id);
lock.lock();   //自旋获取锁
...
...
lock.unlock();

首先记得set water 2

OrderController

	/**** 抢单，使用分布式锁*/@GetMapping(value = "/{id}/{num}")public String add(@PathVariable(value = "id")String id,@PathVariable("num")Long num) throws InterruptedException {//对该商品加锁，加锁成功，则判断库存，避免多人同时判断某一个商品的库存RLock lock = redissonClient.getLock("mylock_" + id);lock.lock();   //自旋获取锁System.out.println("获取了锁！"+lock.getName());try {// 1.查询库存int count = Integer.valueOf(redisTemplate.opsForValue().get(id));System.out.println("剩余库存:"+count);// 2.库存充足if (count>=num){//模拟操作TimeUnit.SECONDS.sleep(5);//递减库存Long decrement = redisTemplate.opsForValue().decrement(id, num);System.out.println("递减库存后剩余库存:"+decrement);//其它操作 略System.out.println("----添加订单了！");return "下单成功";}//库存不足else {return "库存不足";}} finally {//释放锁System.out.println("释放了锁！"+lock.getName());lock.unlock();}}

启动2个服务，浏览器同时发送2个请求
http://127.0.0.1:8080/order/water/2
http://127.0.0.1:8081/order/water/2

防止了超卖现象