Spring Cache简单介绍和使用

Love The Way You Lie 2023-10-11 21:01 57阅读 0赞

**目录**

一、简介

二、使用默认ConcurrentMapManager

（一）创建数据库和表

（二）创建boot项目

（三）使用Api

1、@EnableCaching

2、@CachePut

3、@cacheable

4、@CacheEvict

三、使用redis作为cache

--------------------

## 一、简介 ##

Spring Cache是一个框架，实现了基于注解的缓存功能，只需要简单地加一个注解，就能实现缓存功能。

Spring Cache提供了一层抽象，底层可以切换不同的cache实现。具体就是通过CacheManager接口来统一不同的缓存技术。  
CacheManager是Spring提供的各种缓存技术抽象接口  
针对不同的缓存技术需要实现不同的CacheManager:

![1ae5f86beae84ff785b7930ba5e73a4b.png][]

**CacheManager默认使用的ConcurrentMapManager**

**Spring Cache 常用注解**

![4846e291114a4c5ea9a12675f889419a.png][]

在spring boot项目中，使用缓存技术只需在项目中导入相关缓存技术的依赖包，并在启动类上使用@EnableCaching开启缓存支持即可。  
例如，使用Redis作为缓存技术，只需要导入Spring data Redis的maven坐标即可。

<dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-data-redis</artifactId>
            </dependency>

spring cache的基本api在web下的context包中

![4a23cbe5277b4715a109294a90440c83.png][]

如果有使用其他的api可以导入cache的依赖

<dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-cache</artifactId>
            </dependency>

## 二、使用默认**ConcurrentMapManager**  ##

### （一）创建数据库和表 ###

创建cache\_demo数据库，并创建user表

> create database cache_demo;
    Query OK, 1 row affected (0.02 sec)
    
    > use cache_demo;
    Database changed
    
    > create table user (
    > id bigint primary key,
    > name varchar(50),
    > age int,
    > address varchar(50)
    >);

![9bc0c1e4788b4b6f9889d8da287574af.png][]

### （二）创建boot项目 ###

**改POM**

<?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>2.4.5</version>
            <relativePath/> 
        </parent>
        <groupId>com.itheima</groupId>
        <artifactId>cache_demo</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>
                <scope>compile</scope>
            </dependency>
            <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
                <version>1.18.20</version>
            </dependency>
    
            <dependency>
                <groupId>com.alibaba</groupId>
                <artifactId>fastjson</artifactId>
                <version>1.2.76</version>
            </dependency>
    
            <dependency>
                <groupId>commons-lang</groupId>
                <artifactId>commons-lang</artifactId>
                <version>2.6</version>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-cache</artifactId>
            </dependency>
    
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <scope>runtime</scope>
            </dependency>
    
            <dependency>
                <groupId>com.baomidou</groupId>
                <artifactId>mybatis-plus-boot-starter</artifactId>
                <version>3.4.2</version>
            </dependency>
    
            <dependency>
                <groupId>com.alibaba</groupId>
                <artifactId>druid-spring-boot-starter</artifactId>
                <version>1.1.23</version>
            </dependency>
        </dependencies>
        <build>
            <plugins>
                <plugin>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-maven-plugin</artifactId>
                    <version>2.4.5</version>
                </plugin>
            </plugins>
        </build>
    </project>

**写YML**

server:
      port: 8080
    spring:
      application:
        #应用的名称，可选
        name: cache_demo
      datasource:
        druid:
          driver-class-name: com.mysql.cj.jdbc.Driver
          url: jdbc:mysql://localhost:3306/cache_demo?serverTimezone=Asia/Shanghai&useUnicode=true&characterEncoding=utf-8&zeroDateTimeBehavior=convertToNull&useSSL=false&allowPublicKeyRetrieval=true
          username: root
          password: root
    mybatis-plus:
      configuration:
        #在映射实体或者属性时，将数据库中表名和字段名中的下划线去掉，按照驼峰命名法映射
        map-underscore-to-camel-case: true
        log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
      global-config:
        db-config:
          id-type: ASSIGN_ID

User

@Data
    public class User implements Serializable {
    
        private static final long serialVersionUID = 1L;
    
        private Long id;
    
        private String name;
    
        private int age;
    
        private String address;
    
    }
    
    
    UserMapper
    ====================================================
    @Mapper
    public interface UserMapper extends BaseMapper<User>{
    }
    
    
    UserController
    ====================================================
    @RestController
    @RequestMapping("/user")
    @Slf4j
    public class UserController {
    
        @Autowired
        private UserService userService;
    
        
        // 增加User
        @PostMapping
        public User save(User user){
            userService.save(user);
            return user;
        }
    
    
        // 删除User
        @DeleteMapping("/{id}")
        public void delete(@PathVariable Long id){
            userService.removeById(id);
        }
    
        // 更新User
        @PutMapping
        public User update(User user){
            userService.updateById(user);
            return user;
        }
    
        // 根据id查询User
        @GetMapping("/{id}")
        public User getById(@PathVariable Long id){
            User user = userService.getById(id);
            return user;
        }
    
        // 根据id和name查询User集合
        @GetMapping("/list")
        public List<User> list(User user){
            LambdaQueryWrapper<User> queryWrapper = new LambdaQueryWrapper<>();
            queryWrapper.eq(user.getId() != null,User::getId,user.getId());
            queryWrapper.eq(user.getName() != null,User::getName,user.getName());
            List<User> list = userService.list(queryWrapper);
            return list;
        }
    }

**主启动类**

@Slf4j
    @SpringBootApplication
    public class CacheDemoApplication {
        public static void main(String[] args) {
            SpringApplication.run(CacheDemoApplication.class,args);
            log.info("项目启动成功...");
        }
    }

### （三）使用Api ###

#### 1、@EnableCaching ####

启动类上加注解@EnableCaching // 使用spring cache

#### 2、@CachePut ####

// 在controller中加入缓存对象
        @Autowired
        private CacheManager cacheManager;
    
        /**
         * CachePut：将方法返回值放入缓存
         * value：缓存的名称，每个缓存名称下面可以有多个key
         * key：缓存的key
         */
        @CachePut(value = "userCache",key = "#user.id")
        @PostMapping
        public User save(User user){
            userService.save(user);
            return user;
        }

通过ctrl点进key下载源码后我们可以看到这里使用的是SpEL语言动态获取值

![de62c30b6337402aba349069d57242c7.png][]

测试，使用 postman 发请求

![161e55cebab1490cb76d2301a3ec32b5.png][]

![7a18496717f740bab55ca21a64a6da40.png][]

第一次添加会将返回的user存放进cacheManager中

![4ff13d3869fa468bb37e51ec5fddbc15.png][]

![70dd16d800e64901a4c1074978a310be.png][]

#### 3、@cacheable ####

在方法执行前spring先查看缓存中是否有数据，如果有数据，则直接返回缓存数据；若没有数据，调用方法并将方法返回值放到缓存中

/**
         * Cacheable：在方法执行前spring先查看缓存中是否有数据，如果有数据，则直接返回缓存数据；若没有数据，调用方法并将方法返回值放到缓存中
         * value：缓存的名称，每个缓存名称下面可以有多个key
         * key：缓存的key
         * condition：条件，满足条件时才缓存数据
         * unless：满足条件则不缓存
         */
        @Cacheable(value = "userCache",key = "#id",unless = "#result == null")
        @GetMapping("/{id}")
        public User getById(@PathVariable Long id){
            User user = userService.getById(id);
            return user;
        }

测试，我们使用jack的id去查询一下，同样使用postman，在这个方法设置断点，如果没有触发断点说明是在cache中查询直接返回的

#### 4、@CacheEvict ####

/**
         * CacheEvict：清理指定缓存
         * value：缓存的名称，每个缓存名称下面可以有多个key
         * key：缓存的key
         */
        @CacheEvict(value = "userCache",key = "#p0")
        //@CacheEvict(value = "userCache",key = "#root.args[0]")
        //@CacheEvict(value = "userCache",key = "#id")
        @DeleteMapping("/{id}")
        public void delete(@PathVariable Long id){
            userService.removeById(id);
        }
    
        //@CacheEvict(value = "userCache",key = "#p0.id")
        //@CacheEvict(value = "userCache",key = "#user.id")
        //@CacheEvict(value = "userCache",key = "#root.args[0].id")
        @CacheEvict(value = "userCache",key = "#result.id")
        @PutMapping
        public User update(User user){
            userService.updateById(user);
            return user;
        }

## 三、使用redis作为cache ##

导入redis依赖

<dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-data-redis</artifactId>
            </dependency>

修改YML

server:
      port: 8080
    spring:
      application:
        #应用的名称，可选
        name: cache_demo
      datasource:
        druid:
          driver-class-name: com.mysql.cj.jdbc.Driver
          url: jdbc:mysql://localhost:3306/cache_demo?serverTimezone=Asia/Shanghai&useUnicode=true&characterEncoding=utf-8&zeroDateTimeBehavior=convertToNull&useSSL=false&allowPublicKeyRetrieval=true
          username: root
          password: 123456
      redis:
        host: 192.168.23.100
        port: 6379
        password: zjy123...000
        database: 1
      cache:
        redis:
          time-to-live: 1800000 #设置缓存过期时间，可选
    mybatis-plus:
      configuration:
        #在映射实体或者属性时，将数据库中表名和字段名中的下划线去掉，按照驼峰命名法映射
        map-underscore-to-camel-case: true
        log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
      global-config:
        db-config:
          id-type: ASSIGN_ID

启动项目后，cache变成了RedisCacheManager

![def71fb6bca5419d84b9f422f91e5d25.png][]

使用postman发送save请求

![590764c12b9449a29dc70515c94d6d1e.png][]

db01

![f01b487d9eb440758e5f7dbc8a348329.png][]

发送DELETE删除缓存

![94240ba78cda40d297eaf69d798c1246.png][]

![b3c4b72f4b6444a49e1bf87c194ef940.png][]

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