文章引用：https://mp.weixin.qq.com/s/XgdKE2rBKL0-nFk2NJPuyg

一、单个服务

1.代码

该接口的作用是累加一个值，访问一次该值加1

@RestController
public class LockController {

    @Autowired
    private StringRedisTemplate stringRedisTemplate;

    @GetMapping("/increment")
    public String increment() {
        int counter = Integer.parseInt(stringRedisTemplate.opsForValue().get("count"));
        counter++;
        System.out.println("当前结果：" + counter);
        stringRedisTemplate.opsForValue().set("count", String.valueOf(counter));
        return "结果：" + counter;
    }
}

2.jmeter工具压测

用100个线程，每个线程访问100次去压测，理论上该值最后应该返回10000

3.结果

发生了线程安全问题，部分请求返回结果相同

4.解决办法：加锁

@RestController
public class LockController {

    @Autowired
    private StringRedisTemplate stringRedisTemplate;

    @GetMapping("/increment")
    public synchronized String increment() {
        int counter = Integer.parseInt(stringRedisTemplate.opsForValue().get("count"));
        counter++;
        System.out.println("当前结果：" + counter);
        stringRedisTemplate.opsForValue().set("count", String.valueOf(counter));
        return "结果：" + counter;
    }
}

在非集群模式下，简单上锁能解决线程安全问题。

二、集群模式

代码相同，idea启动两个相同的服务

1.启动两个服务

2.nginx配置负载均衡

upstream backend {
        # 定义后端服务器列表
        server localhost:8081;
        server localhost:8082;
    }
	
	server {
        listen 8080;

        location / {
            # 将请求代理到后端服务器
            proxy_pass http://backend;
        }
    }

3.jmeter工具压测

用100个线程，每个线程访问100次去压测，理论上该值最后应该返回10000


还是出了线程安全问题，synchronized只能锁住单个服务

三、SpringBoot整合Redisson(注解方式)

1.依赖和配置文件

<dependencies>
        <!-- Spring Boot Starter for Web -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <!--         Redisson Dependency-->
        <dependency>
            <groupId>org.redisson</groupId>
            <artifactId>redisson-spring-boot-starter</artifactId>
            <version>3.17.6</version><!-- 请根据需要调整版本 -->
        </dependency>
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjweaver</artifactId>
            <version>1.8.10</version>
        </dependency>
    </dependencies>

spring:
redis:
  host:localhost
  port:6379

# Redisson configuration
redisson:
  single-server-address:redis://@localhost:6379

2.代码

注解

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface DistributedLock {
    String lockName();
}

切面

@Aspect
@Component
public class DistributedLockAspect {

    @Autowired
    private RedissonClient redissonClient;

    @Around("@annotation(DistributedLock)")
    public Object around(ProceedingJoinPoint joinPoint) throws Throwable {
        MethodSignature signature = (MethodSignature) joinPoint.getSignature();
        DistributedLock annotation = signature.getMethod().getAnnotation(DistributedLock.class);
        String lockName = annotation.lockName();

        RLock lock = redissonClient.getLock(lockName);

        try {
            // 尝试获取锁，最多等待10秒，持有锁的时间为30秒
            if (!lock.tryLock(10, 30, TimeUnit.SECONDS)) {
                throw new RuntimeException("Failed to acquire lock.");
            }

            return joinPoint.proceed();
        } finally {
            // 确保在任何情况下都能释放锁
            if (lock.isHeldByCurrentThread()) {
                lock.unlock();
            }
        }
    }
}

接口

@RestController
public class LockController {

    @Autowired
    private StringRedisTemplate stringRedisTemplate;

    @GetMapping("/increment")
    @DistributedLock(lockName = "counterLock")
    public String increment() {
        int counter = Integer.parseInt(stringRedisTemplate.opsForValue().get("count"));
        counter++;
        System.out.println("当前结果：" + counter);
        stringRedisTemplate.opsForValue().set("count", String.valueOf(counter));
        return "结果：" + counter;
    }
}

3.结果

实现了分布式锁，俩个服务依次接受了所有请求，并无重复值