Spring Cache（缓存框架）

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一、Spring Cache是什么？

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缓存实现，例如：

• EHCache
• Caffeine
• Redis

二、常用注解

三、使用步骤

1.导入依赖

Spring Cache缓存框架的maven导入：

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

Spring Cache缓存中间件的导入：

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

总体pom文件如下：

<?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>2.7.3</version>
        <relativePath/>
    </parent>
    <groupId>com.itheima</groupId>
    <artifactId>springcache-demo</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>11</maven.compiler.source>
        <maven.compiler.target>11</maven.compiler.target>
    </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>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-redis</artifactId>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>

        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.2.0</version>
        </dependency>

        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid-spring-boot-starter</artifactId>
            <version>1.2.1</version>
        </dependency>

        <dependency>
            <groupId>com.github.xiaoymin</groupId>
            <artifactId>knife4j-spring-boot-starter</artifactId>
            <version>3.0.2</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <version>2.7.3</version>
            </plugin>
        </plugins>
    </build>
</project>

2.@CachePut的使用

@CachePut：将方法的返回值放到缓存中
案例代码：

    @PostMapping
    //@CachePut(cacheNames = "userCache",key = "#user.id")
    @CachePut(cacheNames = "userCache",key = "#result.id")
    public User save(@RequestBody User user){
        userMapper.insert(user);
        return user;
    }

其中#这种写法是spring规范的。
cacheName：缓存名称，是个字符串
key：缓存数据
如果使用Spring Cache缓存数据，key的生成：userCache：：缓存数据

3.@Cacheable的使用

@Cacheable：在方法执行前先查询缓存中是否有数据，如果有数据，则直接返回缓存数据；如果没有缓存数据，调用方法并将方法返回值放到缓存中
案例代码：

    @GetMapping
    @Cacheable(cacheNames = "userCache",key = "#id")//key的生成：userCache::10
    public User getById(Long id){
        User user = userMapper.getById(id);
        return user;
    }

4.@CacheEvict的使用

@CacheEvict：将一条或多条数据从缓存中删除
清理一条数据案例代码：

    @DeleteMapping
    @CacheEvict(cacheNames = "userCache",key="#id")//key的生成：userCache::10
    public void deleteById(Long id){
        userMapper.deleteById(id);
    }

清理多条数据（cacheNames定义的名字下的所有数据都删除）案例代码：

	@DeleteMapping("/delAll")
    @CacheEvict(cacheNames = "userCache",allEntries = true)
    public void deleteAll(){
        userMapper.deleteAll();
    }

5.@EnableCaching的使用

@EnableCaching：开启缓存注解功能，通常加在启动类上
案例代码：

@SpringBootApplication
@EnableTransactionManagement //开启注解方式的事务管理
@Slf4j
@EnableCaching//开启缓存注解功能
public class SkyApplication {
    public static void main(String[] args) {
        SpringApplication.run(SkyApplication.class, args);
        log.info("server started");
    }
}