Redisson简介

在实际开发中，Redis 其实并没有对 Java 提供原生支持。若想在程序中集成 Redis，就必须使用 Redis 的第三方库。

Redisson就是用于在 Java 程序中操作 Redis 的库，它使得我们可以在程序中轻松地使用Redis。

Redisson 在 java.util 中常用接口的基础上，为我们提供了一系列具有分布式特性的工具类。

案例演示

pom.xml

<packaging>war</packaging>

<dependencies>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-webmvc</artifactId>
        <version>5.2.7.RELEASE</version>
    </dependency>
    <!--实现分布式锁的Redisson工具类-->
    <dependency>
        <groupId>org.redisson</groupId>
        <artifactId>redisson</artifactId>
        <version>3.6.1</version>
    </dependency>
    <!--spring操作redis的工具类-->
    <dependency>
        <groupId>org.springframework.data</groupId>
        <artifactId>spring-data-redis</artifactId>
        <version>2.3.2.RELEASE</version>
    </dependency>
    <!--redis客户端-->
    <dependency>
        <groupId>redis.clients</groupId>
        <artifactId>jedis</artifactId>
        <version>3.1.0</version>
    </dependency>
    <!--json解析工具-->
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>2.9.8</version>
    </dependency>
</dependencies>

<!-- 将Tomcat内嵌到web项目中 -->
<build>
    <plugins>
        <plugin>
            <groupId>org.apache.tomcat.maven</groupId>
            <artifactId>tomcat7-maven-plugin</artifactId>
            <version>2.2</version>
            <configuration>
                <port>8001</port>
                <path>/</path>
            </configuration>
            <executions>
                <execution>
                    <!-- 打包完成后，直接运行服务 -->
                    <phase>package</phase>
                    <goals>
                        <goal>run</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         id="WebApp_ID" version="3.1">

    <servlet>
        <servlet-name>springmvc</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>classpath:spring/spring.xml</param-value>
        </init-param>
    </servlet>
    <servlet-mapping>
        <servlet-name>springmvc</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
</web-app>

Spring配置文件

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns="http://www.springframework.org/schema/beans"
       xsi:schemaLocation="http://www.springframework.org/schema/beans 
                           http://www.springframework.org/schema/beans/spring-beans.xsd 
                           http://www.springframework.org/schema/context 
                           http://www.springframework.org/schema/context/spring-context.xsd">

    <context:component-scan base-package="controller"/>
    <bean id="stringRedisTemplate" class="org.springframework.data.redis.core.StringRedisTemplate">
        <property name="connectionFactory" ref="connectionFactory"/>
    </bean>
    <bean id="connectionFactory" class="org.springframework.data.redis.connection.jedis.JedisConnectionFactory">
        <property name="hostName" value="192.168.204.141"/>
        <property name="port" value="6379"/>
    </bean>
</beans>

Java代码

@Controller
public class TestKill {
    @Autowired
    private Redisson redisson;
    @Autowired
    private StringRedisTemplate stringRedisTemplate;

    @RequestMapping("kill")
    @ResponseBody
    public String kill() {
        // 定义商品id
        String productKey = "Mi 10";
        // 通过redisson获取锁，底层源码集成了setnx，过期时间等操作
        RLock rLock = redisson.getLock(productKey);
        // 上锁（过期时间为30秒）
        rLock.lock(30, TimeUnit.SECONDS);

        try {
            // 1.从redis中获取手机的库存数量
            int phoneCount = Integer.parseInt(stringRedisTemplate.opsForValue().get("phone"));
            // 2.判断手机的数量是否足够用户秒杀
            if (phoneCount > 0) {
                phoneCount--;
                // 库存减少后，再将库存的值保存回redis
                stringRedisTemplate.opsForValue().set("phone", phoneCount + "");
                System.out.println("库存-1，剩余：" + phoneCount);
            } else {
                System.out.println("库存不足！");
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            // 释放锁
            rLock.unlock();
        }
        return "over!";
    }

    @Bean
    public Redisson redisson() {
        Config config = new Config();
        // 使用单个redis服务器
        config.useSingleServer().setAddress("redis:192.168.204.141:6379").setDatabase(0);
        // 使用集群redis，本案例使用单个redis服务器进行演示，所以注释掉
        // config.useClusterServers().setScanInterval(2000).addNodeAddress("redis:192.168.204.141:6379", "redis:192.168.204.142:6379", "redis:192.168.204.143:6379");
        return (Redisson) Redisson.create(config);
    }
}