1、Redis简介
Redis是一个开源的key-value存储系统。
Redis的五种基本类型:String(字符串),list(链表),set(集合),zset(有序集合),hash,stream(Redis5.0后的新数据结构)
这些数据类型都支持push/pop、add/remove及取交集并集和差集及更丰富的操作,而且这些操作都是原子性的。
Redis的应用场景为配合关系型数据库做高速缓存,降低数据库IO
需要注意的是,Redis是单线程的,如果一次批量处理命令过多,会造成Redis阻塞或网络拥塞(传输数据量大)
2、实现代码
pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<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>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.2.1.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>org.example</groupId>
<artifactId>seckill</artifactId>
<version>1.0-SNAPSHOT</version>
<properties>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-starter-test -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<version>2.2.1.RELEASE</version>
<scope>test</scope>
</dependency>
<!-- redis -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>
<!-- spring2.X集成redis所需common-pool2-->
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-pool2</artifactId>
<version>2.6.0</version>
</dependency>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>fastjson</artifactId>
<version>1.2.24</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<configuration>
<fork>true</fork>
</configuration>
</plugin>
</plugins>
</build>
</project>
application.properties.xml
#Redis服务器地址
spring.redis.host=192.168.1.2
#Redis服务器连接端口
spring.redis.port=6379
#Redis数据库索引(默认为0)
spring.redis.database=0
#连接超时时间(毫秒)
spring.redis.timeout=1800000
#连接池最大连接数(使用负值表示没有限制)
spring.redis.lettuce.pool.max-active=20
#最大阻塞等待时间(负数表示没限制)
spring.redis.lettuce.pool.max-wait=-1
#连接池中的最大空闲连接
spring.redis.lettuce.pool.max-idle=5
#连接池中的最小空闲连接
spring.redis.lettuce.pool.min-idle=0
# 关闭超时时间
#pring.redis.lettuce.shutdown-timeout=100
#配置spring启动端口号
server.port=8080
前端界面
seckillpage.html
<!DOCTYPE html>
<html lang="en" xmlns:v-on="http://www.w3.org/1999/xhtml" xmlns:v-bind="http://www.w3.org/1999/xhtml">
<head>
<meta charset="UTF-8">
<title>redis秒杀</title>
</head>
<body>
<!-- 开发环境版本,包含了有帮助的命令行警告 -->
<script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
<!-- 官网提供的 axios 在线地址 -->
<script src="https://cdn.bootcdn.net/ajax/libs/axios/0.20.0-0/axios.min.js"></script>
<div id="app">
<h1>商品1元秒杀</h1>
<!-- 左箭头 -->
<input type="button" value="<" v-on:click="prov" v-show="this.index>-1"/>
<img v-bind:src="imgArr[index]" width="200px" />
<!-- 右箭头 -->
<input type="button" value=">" v-on:click="next" v-show="this.index<2"/><br>
<input type="button" v-on:click="seckill" value="秒 杀"/>
</div>
<script>
var app = new Vue({
el: "#app",
data: {
productId: "01234",
imgArr:[
"/image/phone1.png",
"/image/phone2.png",
"/image/phone3.png",
],
index:0
},
methods: {
seckill: function () {
let param = new URLSearchParams()
param.append('productId', this.productId)
param.append('index', this.index)
axios({
method: 'post',
url: 'http://192.168.1.6:8080/index/doSeckill',
data: param
}).then(function (response) {
if (response.data == true) {
alert("秒杀成功");
} else {
alert("抢光了");
}
},
function(error){
alert("发生错误");
});
},
prov:function(){
this.index--;
},
next:function(){
this.index++;
}
}
});
</script>
</body>
</html>
相关配置类
Redis配置类
RedisConfig.java
package com.springboot_redis_seckill.config;
import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.PropertyAccessor;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.cache.CacheManager;
import org.springframework.cache.annotation.CachingConfigurerSupport;
import org.springframework.cache.annotation.EnableCaching;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.redis.cache.RedisCacheConfiguration;
import org.springframework.data.redis.cache.RedisCacheManager;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.serializer.Jackson2JsonRedisSerializer;
import org.springframework.data.redis.serializer.RedisSerializationContext;
import org.springframework.data.redis.serializer.RedisSerializer;
import org.springframework.data.redis.serializer.StringRedisSerializer;
import java.time.Duration;
@EnableCaching
@Configuration
public class RedisConfig extends CachingConfigurerSupport {
@Bean
public RedisTemplate<String, Object> redisTemplate(RedisConnectionFactory factory) {
RedisTemplate<String, Object> template = new RedisTemplate<>();
RedisSerializer<String> redisSerializer = new StringRedisSerializer();
Jackson2JsonRedisSerializer jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer(Object.class);
ObjectMapper om = new ObjectMapper();
om.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);
om.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
jackson2JsonRedisSerializer.setObjectMapper(om);
template.setConnectionFactory(factory);
template.setKeySerializer(redisSerializer); //key序列化方式
template.setValueSerializer(jackson2JsonRedisSerializer); //value序列化
template.setHashValueSerializer(jackson2JsonRedisSerializer); //value hashmap序列化
return template;
}
@Bean(name = "cacheManager")
public CacheManager cacheManager(RedisConnectionFactory factory) {
RedisSerializer<String> redisSerializer = new StringRedisSerializer();
Jackson2JsonRedisSerializer jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer(Object.class);
//解决查询缓存转换异常的问题
ObjectMapper om = new ObjectMapper();
om.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);
om.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
jackson2JsonRedisSerializer.setObjectMapper(om);
// 配置序列化(解决乱码的问题),过期时间600秒
RedisCacheConfiguration config = RedisCacheConfiguration.defaultCacheConfig()
.entryTtl(Duration.ofSeconds(600))
.serializeKeysWith(RedisSerializationContext.SerializationPair.fromSerializer(redisSerializer))
.serializeValuesWith(RedisSerializationContext.SerializationPair.fromSerializer(jackson2JsonRedisSerializer))
.disableCachingNullValues();
RedisCacheManager cacheManager = RedisCacheManager.builder(factory)
.cacheDefaults(config)
.build();
return cacheManager;
}
}
配置Vue获取后端接口数据时出现的跨域请求问题。
CorsConfig.java
package com.springboot_redis_seckill.config;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.cors.CorsConfiguration;
import org.springframework.web.cors.UrlBasedCorsConfigurationSource;
import org.springframework.web.filter.CorsFilter;
@Configuration
public class CorsConfig {
private CorsConfiguration buildConfig() {
CorsConfiguration corsConfiguration = new CorsConfiguration();
corsConfiguration.addAllowedOrigin("*"); //允许任何域名
corsConfiguration.addAllowedHeader("*"); //允许任何头
corsConfiguration.addAllowedMethod("*"); //允许任何方法
return corsConfiguration;
}
@Bean
public CorsFilter corsFilter() {
UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource();
source.registerCorsConfiguration("
@Service
public class SecKillServiceImpl implements SecKillService {
@Autowired
@Qualifier("redisTemplate")
private RedisTemplate redisTemplate;
@Override
public synchronized boolean doSecKill(String uid, String productId) {
//1、uid和productId非空判断
if (uid == null || productId == null) {
return false;
}
//2、拼接key
String kcKey = "sk:" + productId + ":qt"; //库存
String userKey = "sk:" + productId + ":user"; //秒杀成功的用户
//3、获取库存
String kc = String.valueOf(redisTemplate.opsForValue().get(kcKey)) ;
if (kc == null) {
System.out.println("秒杀还没有开始,请等待");
return false;
}
//4、判断用户是否已经秒杀成功过了
if (redisTemplate.opsForSet().isMember(userKey, uid)) {
System.out.println("已秒杀成功,不能重复秒杀");
return false;
}
//5、如果库存数量小于1,秒杀结束
if (Integer.parseInt(kc) <=0) {
System.out.println("秒杀结束");
return false;
}
//6、秒杀过程
redisTemplate.opsForValue().decrement(kcKey); //库存数量减1
redisTemplate.opsForSet().add(userKey, uid);
System.out.println("秒杀成功。。。");
return true;
}
}
控制层
package com.springboot_redis_seckill.controller;
import com.alibaba.fastjson.JSONObject;
import com.springboot_redis_seckill.service.SecKillService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Random;
@Controller
@RequestMapping("/index")
public class MyController {
@Autowired
@Qualifier("secKillServiceImpl")
private SecKillService secKillService;
@RequestMapping(value = {"/seckillpage"}, method = RequestMethod.GET)
public String seckillpage() {
return "/html/seckillpage.html";
}
@RequestMapping(value = {"/doSeckill"}, method = RequestMethod.POST)
@ResponseBody //自动返回json格式的数据
public Object doSeckill(HttpServletRequest request, HttpServletResponse response) {
System.out.println("doSeckill");
String productId = request.getParameter("productId");
String index = request.getParameter("index");
System.out.println(productId+index); //拼接成为商品ID
int id = new Random().nextInt(50000); //使用随机数生成用户ID
String uid = String.valueOf(id) + " ";
boolean flag = secKillService.doSecKill(uid, productId+index);
System.out.println(flag);
return flag;
}
}
启动类
RunApplication.java
package com.springboot_redis_seckill;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class RunApplication {
public static void main(String[] args) {
SpringApplication.run(RunApplication.class, args);
}
}
3、启动步骤
因为一共有三件商品要秒杀,所以在redis里面设置三个商品的库存数量。这里数量都设置为10。
127.0.0.1:6379> set sk:012340:qt 10
OK
127.0.0.1:6379> set sk:012341:qt 10
OK
127.0.0.1:6379> set sk:012342:qt 10
OK
要确保redis能够被访问,要确保关闭linux的防火墙,以及关闭redis的保护模式。
vim redis.conf --打开redis配置
service iptables stop --关闭防火墙
//关闭redis保护模式
redis-cli --进入redis客户端
config set protected-mode "no" --配置里面关闭redis保护模式(只是进入redis.conf把protected-mode变为no是不行的,还要加一句config set protected-mode "no"
启动springboot项目
秒杀成功后,该商品在redis中的数量就减1。
当数量减为0时,则提示“抢光了”。
4、使用ab进行并发测试
如果是centOS 6版本的linux都是默认按照了ab工具的。
如果没有安装ab工具,可在linux终端用命令联网下载安装。
yum install httpd-tools
安装完成后,就可以使用ab工具进行并发测试了。
在linux终端输入如下命令:
ab -n 2000 -c 200 -p '/root/Desktop/post.txt' -T 'application/x-www-form-urlencoded' 'http://192.168.1.6:8080/index/doSeckill/'
012341这个商品库存变为0了
5、线程安全
为了防止出现“超买”的现象,需要让操作redis的方法是线程安全的(即在方法上加上一个“悲观锁”synchronized)。
如果不加synchronized就会出现“超买”现象,即redis库存会出现负数
之所以产生这种现象是由于并发导致多个用户同时调用了doSecKill()方法,多个用户同时修改了redis中的sk:012342:qt的值,但暂时都没有提交存入到redis中去。等到后来一起提交,导致了sk:012342:qt的值被修改了多次,因此会出现负数。
因此在doSecKill()方法加上悲观锁,用户调用该方法就对该方法加锁,修改了sk:012342:qt的值后并提交存入redis中之后,才会释放锁。其他用户才能得到锁并操作该方法。
6、总结
redis作为一种Nosql的非关系型数据库,因为其单实例,简单高效的特性通常会被作为其他关系型数据库的高速缓存。尤其是在秒杀这样的高并发操作。先将要秒杀的商品信息从数据库读入到redis中,秒杀的过程实际上是在与redis进行交互。等秒杀完成后再将秒杀的结果存入数据库。可以有效降低降低数据库IO,防止数据库宕机。
7、参考资料
https://www.bilibili.com/video/BV1Rv41177Af?p=27
https://www.cnblogs.com/taiyonghai/p/5810150.html
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