（Redis）使用Redisson实现分布式锁

1、引入依赖

具体依赖

这两个依赖版本如果选择不对的话，会造成依赖冲突

        <!--Redis依赖-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-redis</artifactId>
            <version>2.7.16</version>
        </dependency>
        <!--Redisson依赖-->
        <dependency>
            <groupId>org.redisson</groupId>
            <artifactId>redisson-spring-boot-starter</artifactId>
            <version>3.18.0</version>
        </dependency>

整体依赖

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>com.xu</groupId>
  <artifactId>redisson_demo</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>maven-plugin</packaging>

  <name>redisson_demo Maven Plugin</name>

  <!-- FIXME change it to the project's website -->
  <url>http://maven.apache.org</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <parent>
    <artifactId>spring-boot-starter-parent</artifactId>
    <groupId>org.springframework.boot</groupId>
    <version>2.3.5.RELEASE</version>
  </parent>

  <dependencies>

    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-test</artifactId>
      <scope>test</scope>
    </dependency>

    <!--Redis依赖-->
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-data-redis</artifactId>
      <version>2.7.16</version>
    </dependency>
    <!--Redisson依赖-->
    <dependency>
      <groupId>org.redisson</groupId>
      <artifactId>redisson-spring-boot-starter</artifactId>
      <version>3.18.0</version>
    </dependency>

  </dependencies>
</project>

2、配置编写（application.yml）

使用 redisson-spring-boot-starter 而不是 redisson 的话，就不需要手动配置RedissonClient类了。会默认使用redis的配置。

server:
  port: 8080

spring:
  redis:
    host: localhost
    port: 6379
    password: 112233

3、实现分布式锁

package com.xu.service;

import org.redisson.api.RLock;
import org.redisson.api.RedissonClient;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.concurrent.TimeUnit;

@Service
public class RedissonService {

	// 直接注入的话，我这边会调用失败，显示没有注入到容器中，下面手动注入就没有问题。
	// @Autowired
	// private RedissonClient redissonClient;

	int size = 0;
    private RedissonClient redissonClient;
    
    @Autowired
    public RedissonService(RedissonClient redissonClient){
        this.redissonClient = redissonClient;
    }

    public void yourMethod() {
        // 获取锁对象
        RLock lock = redissonClient.getLock("yourLockKey");
        try {
            // 尝试加锁，等待时间为15秒，锁的持有时间为30秒
            if (lock.tryLock(15, 30, TimeUnit.SECONDS)) {
            	// 编写业务逻辑的位置

                System.out.println("等待中.....");
                // 线程睡眠3秒，模拟排队
                Thread.sleep(3000);
                
                System.out.println("调用完成，第" + size++ + "调用!!!");
                
            }
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
        } finally {
            // 释放锁
            if (lock.isLocked() && lock.isHeldByCurrentThread()) {
                lock.unlock();
            }
        }
    }

}

4、结果演示

1. 编写接口

package com.xu.controller;

import com.xu.service.RedissonService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class DemoController {
    
    @Autowired
    RedissonService redissonService;
    
    @GetMapping("/demo")
    public void demo() {
        redissonService.yourMethod();
    }
}

2. ApiPost模拟多次调用

3. Redis数据库中的锁元素的展示