缓存应用场景
什么是缓存？
在互联网场景下，尤其 2C 端大流量场景下，需要将一些经常展现和不会频繁变更的数据，存放在存取速率更快的地方。缓存就是一个存储器，在技术选型中，常用 Redis 作为缓存数据库。缓存主要是在获取资源方便性能优化的关键方面
缓存的应用场景有哪些呢？
比如常见的电商场景，根据商品 ID 获取商品信息时，店铺信息和商品详情信息就可以缓存在 Redis，直接从 Redis 获取。减少了去数据库查询的次数。但会出现新的问题，需要对缓存进行更新，防止数据读入错误
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Redis在CENTOS7中安装
daemonize设置为yes，设置为后台启动
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运行在主机ip，端口6379地址
springboot整合redis-使用Jedis客户端
创建springboot工程
工程目录如下
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pom文件
<?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>
<groupId>com.enowsh.springboot_redis</groupId>
<artifactId>demo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>demo</name>
<description>Demo project for Spring Boot</description>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.2.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-redis</artifactId>
<exclusions>
<exclusion>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
<exclusions>
<exclusion>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
<version>1.3.2</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>druid</artifactId>
<version>1.0.9</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<version>1.7.25</version>
</dependency>
<dependency>
<groupId>com.github.pagehelper</groupId>
<artifactId>pagehelper</artifactId>
<version>3.4.2</version>
</dependency>
<dependency>
<groupId>redis.clients</groupId>
<artifactId>jedis</artifactId>
<version>2.9.0</version>
</dependency>
<dependency>
<groupId>commons-lang</groupId>
<artifactId>commons-lang</artifactId>
<version>2.6</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
注意：要在两个地方去掉logback-classic包，不然会报错
springboot整合mybatis
引入mapper文件，配置数据源以及mybatis等的配置，此处不再赘述
配置Jedis客户端
application.properties设置redis的属性
#redis配置
redis.host=192.168.73.128
redis.port=6379
#用户缓存key配置
REDIS_USER_KEY=REDIS_USER_KEY
写config类，配置Jedis
package com.enowsh.springboot_redis.config.redis;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;
import redis.clients.jedis.JedisPoolConfig;
/**
* @author:wong
*/
@Configuration
public class RedisConfig {
@Value("${redis.host}")
private String host;
@Value("${redis.port}")
private int port;
@Bean
public JedisPool jedisPool(){
JedisPoolConfig jedisPoolConfig = new JedisPoolConfig();
JedisPool jedisPool = new JedisPool(jedisPoolConfig, host, port);
return jedisPool;
}
@Bean
public Jedis jedis(){
Jedis jedis = jedisPool().getResource();
return jedis;
}
}
注意点：
- 使用@Value注解引入属性
- 创建JedisPool的bean，初始化构造函数参数，分别是：JedisPoolConfig对象，主机地址，端口号
- 为了使用方便，配置Jedis的bean
编写service测试
package com.enowsh.springboot_redis.service.impl;
import com.enowsh.springboot_redis.mapper.PmsUserMapper;
import com.enowsh.springboot_redis.pojo.PmsResult;
import com.enowsh.springboot_redis.pojo.PmsUser;
import com.enowsh.springboot_redis.service.UserService;
import com.enowsh.springboot_redis.utils.JsonUtils;
import org.apache.commons.lang.StringUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import redis.clients.jedis.Jedis;
import java.util.Date;
/**
* @author:wong
*/
@Service
@Transactional //默认开启所有public方法的事务
public class UserServiceImpl implements UserService {
@Autowired
private PmsUserMapper pmsUserMapper;
@Autowired
private Jedis jedis;
@Value("${REDIS_USER_KEY}")
private String REDIS_USER_KEY;
@Override
public PmsResult getUserById(long id) {
//添加查询缓存逻辑
try {
String s = jedis.hget(REDIS_USER_KEY,id+"");
if (!StringUtils.isBlank(s)){
PmsUser pmsUser=JsonUtils.jsonToPojo(s,PmsUser.class);
return PmsResult.ok(pmsUser);
}
}catch (Exception e){
e.printStackTrace();
}
PmsUser pmsUser = pmsUserMapper.selectByPrimaryKey(id);
if (pmsUser==null)
return PmsResult.build(400,"未查询到用户");
else {
//添加写入缓存逻辑,将用户信息写入缓存，以json串的模式写入
try {
jedis.hset(REDIS_USER_KEY ,id+"", JsonUtils.objectToJson(pmsUser));
//设置用户信息有效期,一天过期
jedis.expire(REDIS_USER_KEY ,86400);
}catch (Exception e){
e.printStackTrace();
}
return PmsResult.ok(pmsUser);
}
}
@Override
public PmsResult getUserByIdentity(int identity) {
return null;
}
@Override
public PmsResult addUser(PmsUser user) {
//添加删除缓存逻辑,问题是如何删除一类用户
try{
jedis.del(REDIS_USER_KEY);
}catch (Exception e){
e.printStackTrace();
}
if (user==null)
return PmsResult.build(400,"用户为空");
Date date=new Date();
user.setCreated(date);
user.setUpdated(date);
pmsUserMapper.insert(user);
return PmsResult.ok();
}
@Override
public PmsResult testRedis() {
String a = jedis.get("a");
return PmsResult.ok(a);
}
@Override
public PmsResult deleteUserById(long id) {
return null;
}
@Override
public PmsResult updateUser(PmsUser user) {
return null;
}
}
测试点：
- 查询数据：先从缓存中查询，如果命中，则返回数据，如果未命中，则从数据库中查询，并将数据写入缓存。此处写缓存使用Jedis的hset方法，利于统一规划管理
- 操作数据：操作数据时，为了防止更新后还是读缓存原来的数据，导致错误，需要清空缓存
controller
package com.enowsh.springboot_redis.controller;
import com.enowsh.springboot_redis.pojo.PmsResult;
import com.enowsh.springboot_redis.pojo.PmsUser;
import com.enowsh.springboot_redis.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.MediaType;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
/**
* @author:wong
*/
@Controller
@RequestMapping("/user")
public class UserController {
@Autowired
private UserService userService;
@RequestMapping("/find/{id}")
@ResponseBody
public PmsResult findUserById(@PathVariable long id){
PmsResult pmsResult= userService.getUserById(id);
return pmsResult;
}
@RequestMapping("/test/redis")
@ResponseBody
public PmsResult testRedis(){
PmsResult pmsResult = userService.testRedis();
return pmsResult;
}
@RequestMapping(value = "/add",method = RequestMethod.POST)
@ResponseBody
public PmsResult addUser(PmsUser user,String username){
PmsResult pmsResult = userService.addUser(user);
return pmsResult;
}
}
测试结果
get请求：http://localhost:8080/user/find/44
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缓存 ：
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post请求：http://localhost:8080/user/add
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缓存:
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