在SpringBoot中使用Redis缓存

前言

本项目主要采用H2作为数据库，Durid作为连接池，JPA作为持久层框架，Redis作为缓存。

注：本章与之前的使用H2Database+Druid连接池+Spring Data JPA+Ehcache实现CRUD操作，大同小异，所不同的是这里使用的是Redis缓存。如果相关概念不清楚，请查看上篇。

 一、导入依赖包

<?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>2.1.2.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.scb</groupId>
    <artifactId>springboot-demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>springboot-demo</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-aop</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>1.1.11</version>
        </dependency>

        <!-- Using JSP -->
        <dependency>
            <groupId>org.apache.tomcat.embed</groupId>
            <artifactId>tomcat-embed-jasper</artifactId>
            <version>8.5.31</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
            <version>1.2</version>
            <scope>provided</scope>
        </dependency>

        <!-- Using Redis -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-redis</artifactId>
            <!-- 不依赖Redis的异步客户端lettuce -->
            <exclusions>
                <exclusion>
                    <groupId>io.lettuce</groupId>
                    <artifactId>lettuce-core</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>redis.clients</groupId>
            <artifactId>jedis</artifactId>
        </dependency>

        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <!-- 阿里系的Druid依赖包 -->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid-spring-boot-starter</artifactId>
            <version>1.1.9</version>
        </dependency>
        <!-- Druid 依赖 log4j包 -->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

二、配置缓存管理器

Spring在使用缓存注解前，需要配置缓存管理器，缓存管理器将提供一些重要的信息，如缓存类型、超时时间等。

在SpringBoot中配置缓存管理器很简单，只需要在application.yml中配置相关细节，SpringBoot就会自动装配他。

spring:
#使用jsp视图
  mvc:
    view:
      prefix: /WEB-INF/jsp/
      suffix: .jsp
#配置Redis的缓存管理器
  cache:
    cache-names: redisCache
    type: redis
#redis配置
  redis:
    port: 6379
    host: localhost
    jedis:
      pool:
        min-idle: 5
        max-active: 10
        max-idle: 10
#配置JPA
  jpa:
    generate-ddl: false
    show-sql: true #print DB sql
    hibernate:
      ddl-auto: update
#配置h2数据库
  h2:
    console:
      path: /h2-console
      enabled: true
      settings:
        web-allow-others: true
  datasource:
    platform: h2
    url: jdbc:h2:~/user
    username: sa
    password:
    name: test
#使用druid连接池
    type: com.alibaba.druid.pool.DruidDataSource
    druid:
      min-idle: 2
      initial-size: 5
      max-active: 10
      max-wait: 5000
      validation-query: select 1
server:
  port: 8090

然后我们还需要在Application主类（SpringBoot的运行类）中加上@EnableCaching

package com.scb.springbootdemo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cache.annotation.EnableCaching;

@SpringBootApplication
@EnableCaching    //启动缓存机制
public class SpringbootDemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpringbootDemoApplication.class, args);
    }

}

这样，使用Redis作为缓存就配置好了。

三、实体层开发

package com.scb.springbootdemo.entity;

import lombok.Data;

import javax.persistence.*;
import java.io.Serializable;

@Data
@Entity(name = "user")
public class User implements Serializable {
    private static final long serialVersionUID = 5150128533924554727L;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    @Column(name = "userName",nullable = false)
    private String userName;
    @Column(name = "note",nullable = false)
    private String note;
}

四、dao层

package com.scb.springbootdemo.repository;

import com.scb.springbootdemo.entity.User;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

import java.util.List;

@Repository
public interface UserRepository extends JpaRepository<User,Long> {
    List<User> findByUserNameAndNote(String username, String note);
}

五、service层

package com.scb.springbootdemo.service;

import com.scb.springbootdemo.entity.User;

import java.util.List;

public interface IUserService {
    User getUser(Long id);
    List<User> getAllUsers();
    User insertUser(User user);
    User updateUserName(Long id,String userName);
    List<User> findUsers(String userName,String note);
    void deleteUser(Long id);
}

package com.scb.springbootdemo.service;

import com.scb.springbootdemo.entity.User;
import com.scb.springbootdemo.repository.UserRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cache.annotation.CacheEvict;
import org.springframework.cache.annotation.CachePut;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.util.List;

@Service
@Transactional
public class UserServiceImpl implements IUserService {
    @Autowired
    UserRepository userRepository;

    @Override
    @Cacheable(value = "redisCache",key = "'redis_user_'+#id")
    public User getUser(Long id) {
        return userRepository.getOne(id);
    }

    @Override
    public List<User> getAllUsers() {
        return userRepository.findAll();
    }

    @Override
    @CachePut(value = "redisCache",key = "'redis_user_'+#result.id")
    public User insertUser(User user) {
        return userRepository.save(user);
    }

    @Override
    @CachePut(value = "redisCache",condition = "#result != 'null'",key = "'redis_user_'+#id")
    public User updateUserName(Long id, String userName) {
        User user=this.getUser(id);
        if(user == null){
            return null;
        }
        user.setUserName(userName);
        return userRepository.save(user);
    }

    @Override
    public List<User> findUsers(String userName, String note) {
        return userRepository.findByUserNameAndNote(userName,note);
    }

    @Override
    @CacheEvict(value = "redisCache",key = "'redis_user_'+#id",beforeInvocation = false)
    public void deleteUser(Long id) {
        userRepository.deleteById(id);
    }
}

六、controller层

package com.scb.springbootdemo.controller;

import com.scb.springbootdemo.entity.User;
import com.scb.springbootdemo.service.IUserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@RequestMapping(path = "/user",produces="application/json;charset=utf-8")
public class RedisCachingController {
    @Autowired
    IUserService userService;

    @GetMapping("/{id}")
    public User getUser(@PathVariable Long id){
        return userService.getUser(id);
    }

    @GetMapping
    public List<User> getAllUsers(){
        return userService.getAllUsers();
    }

    @GetMapping("/{userName}/{note}")
    public List<User> findUsers(@PathVariable String userName,@PathVariable String note){
        return userService.findUsers(userName,note);
    }

    @PostMapping("/{userName}/{note}")
    public User insertUser(@PathVariable String userName,@PathVariable String note){
        User user=new User();
        user.setUserName(userName);
        user.setNote(note);
        return userService.insertUser(user);
    }

    @PutMapping("/{id}/{userName}")
    public User updateUserName(@PathVariable Long id,@PathVariable String userName){
        return userService.updateUserName(id,userName);
    }

    @DeleteMapping("/{id}")
    public void deleteUser(@PathVariable Long id){
        userService.deleteUser(id);
    }

}

七、测试

上面项目已经开发完毕，下面我们运行项目，并使用postman进行测试。

以post请求访问http://localhost:8090/user/zhang/san，是新建一个user对象。然后我们在Redis客户端查看是否存入：

可以看到，缓存已经存入。

通过查看该key的超时时间，可以发现是-1，这代表该缓存永不过期。这是很糟糕的，我们一般对于缓存都需要设置一个超时时间，具体配置如下：

八、自定义Redis缓存管理器

在上面RedisConfig配置类中，加入以下配置信息。

    //自定义Redis缓存管理器
    @Bean
    public RedisCacheManager redisCacheManager(RedisConnectionFactory redisConnectionFactory){
        //Redis加锁的写入器
        RedisCacheWriter writer = RedisCacheWriter.lockingRedisCacheWriter(redisConnectionFactory);
        //启动Redis缓存的默认设置
        RedisCacheConfiguration cacheConfiguration=RedisCacheConfiguration.defaultCacheConfig();
        //设置JDK序列化器
        cacheConfiguration=cacheConfiguration.serializeValuesWith(RedisSerializationContext.SerializationPair.fromSerializer(new JdkSerializationRedisSerializer()));
        //禁用前缀
        cacheConfiguration=cacheConfiguration.disableKeyPrefix();
        //设置10min超时时间
        cacheConfiguration=cacheConfiguration.entryTtl(Duration.ofMinutes(10));
        //创建Redis缓存管理器
        RedisCacheManager redisCacheManager=new RedisCacheManager(writer,cacheConfiguration);
        return redisCacheManager;
    }

此时，在以post请求访问http://localhost:8090/user/zhang/san，新建一个user对象。然后我们在Redis客户端查看：

可以看到新创建的key不仅去掉了"redisCache"前缀，而且设置了一个10分钟的超时时间。

当超过10分钟时，超时时间显示为-2，这表示已经过期。此时，在取key的值时，将会为空（nil）