【springboot】缓存之@Cacheable、@CachePut、@CacheEvict的用法

一、注解参数说明

1.1 属性说明

1.1.1 value/cacheNames 属性

• 1.这两个属性代表的意义相同
• 2.用来指定缓存组件的名称，将方法的返回结果存进缓存的名称
• 3.定义为数组时，可以存到多个缓存key中

1.1.2 key属性

• 1.指定缓存数据的key

1.#root.method.name：当前被调用的方法名
2.#root.methodName：当前被调用的方法
3.#root.target：当前被调用的目标对象
4.#root.targetClass：当前被调用的目标对象类
5.#root.args[0]：当前被调用的方法的参数列表
6.#root.caches[0].name：当前方法调用使用的缓存列表（@Cacheable(value={"cache1","cache2"})）
7.#id、#p0、#a0：方法参数的名字，可以#参数名，也可以使用 #p0或#a0 的形式，0代表参数的索引
8.#result：方法执行后的返回值（仅当方法执行之后的判断有效，如’unless’、@cacheput和@cacheevict的表达式beforeInvocation=false）

• 2.redis作为缓存时，redis中的key为value::key
• 3.方法没有参数时，key=new SimpleKey()
• 4.方法有一个参数时，key=参数的值
• 5.方法有多个参数时，key=new SimpleKey(params)；

1.1.3 keyGenerator属性

• 1.key 的生成器
• 2.可以自定义key的生成器的组件id
• 3.key与keyGenerator二选一使用
• 4.可以自定义配置类，将 keyGenerator 注册到 IOC 容器

1.1.4 cacheManager属性

• 1.用来指定缓存管理器
• 2.对不同的缓存技术，实现不同的cacheManager，spring定义了一些 cacheManger的实现
• 3.SimpleCacheManager：使用简单的Collection来存储缓存（默认）
• 4.ConcurrentMapCacheManager：使用ConcurrentMap作为缓存技术
• 5.NoOpCacheManager：测试用
• 6.EhCacheCacheManager：使用EhCache作为缓存技术，hibernate经常用
• 7.GuavaCacheManager：使用google的guava的GuavaCache作为缓存技术
• 8.HazelcastCacheManager：使用Hazelcast作为缓存技术
• 9.JCacheCacheManager：使用JCache标准的实现作为缓存技术，如Apache Commons JCS
• 10.RedisCacheManager：使用Redis作为缓存技术

1.1.5 cacheResolver属性

• 1.指定自定义的缓存管理器
• 2.cacheManager缓存管理器与cacheResolver自定义解析器二选一使用

1.1.6 condition属性

• 1.符合指定的条件才可以缓存
• 2.可以通过 SpEL 表达式进行设置

1.1.7 unless 属性

• 1.unless的条件为 true 时，方法的返回值不会被缓存
• 2.可以在获取到结果后进行判断

1.1.8 sync 属性

• 1.是否使用同步模式
• 2.异步模式下 unless 属性不可用
• 3.sync=true：同步模式，若多个线程尝试为同一个key缓存值，当一个线程缓存成功后，其它线程便直接拿缓存后的数据，不会再去查库缓存，能解决缓存击穿问题；一个线程去新建，新建成功后其它线程才能拿
• 4.默认是false

1.2 @Cacheable注解

• 1.每次执行方法前都会检查cache中是否存在相同key的缓存，如果存在就不再执行该方法，直接从缓存中获取结果进行返回，如果不存在则会执行该方法并将结果存入指定key的缓存中

1.3 @CachePut注解

• 1.在执行方法前不会去检查缓存中是否存在key的缓存，每次都会执行该方法，并将执行结果存入指定key的缓存中
• 2.使用在保存，更新方法中
• 3.标注在类上和方法

1.4 @CacheEvict注解

• 1.标注在需要清除缓存的方法或类
• 2.标记在类上时表示其中所有方法的执行都会触发缓存的清除操作
• 3.@CacheEvict可以指定的属性有value、key、condition、allEntries和beforeInvocation

1.4.1 allEntries属性

• 1.allEntries为true时，清除value属性值中的所有缓存，更有效率
• 2.默认为false，可以指定清除value属性值下具体某个key的缓存

1.4.2 beforeInvocation属性

• 1.默认是false，即在方法执行成功后触发删除缓存的操作
• 2.如果方法抛出异常未能成功返回，不会触发删除缓存的操作
• 3.当改为true时，方法执行之前会清除指定的缓存，这样不论方法执行成功还是失败都会清除缓存

二、代码示例

2.1 基本框架搭建

• 1.导入依赖

<?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"><parent><artifactId>springboot-learning</artifactId><groupId>com.learning</groupId><version>1.0-SNAPSHOT</version></parent><modelVersion>4.0.0</modelVersion><artifactId>springboot-cache</artifactId><properties><maven.compiler.source>8</maven.compiler.source><maven.compiler.target>8</maven.compiler.target></properties><dependencies><!-- springboot web启动类--><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId></dependency><!-- mybatis-plus依赖包 --><dependency><groupId>com.baomidou</groupId><artifactId>mybatis-plus-boot-starter</artifactId><version>3.4.2</version></dependency><!-- mysql依赖包 --><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><scope>runtime</scope></dependency><!-- cache依赖 --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-cache</artifactId></dependency><!-- 用redis作为缓存 --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-data-redis</artifactId></dependency></dependencies>
</project>

• 2.application.yaml配置

spring:datasource:url: jdbc:mysql://localhost:3306/test?serverTimezone=UTC&useUnicode=true&characterEncoding=utf-8&useSSL=falsedriver-class-name: com.mysql.cj.jdbc.Driverusername: rootpassword: rootcache:type: redisredis:host: 127.0.0.1port: 6379
mybatis-plus:global-config:db-config:id-type: autoconfiguration:log-impl: org.apache.ibatis.logging.stdout.StdOutImpl

• 3.接口类

package com.learning.cache.controller;import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.learning.cache.entity.Student;
import com.learning.cache.service.StudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;import java.util.List;/* @Description 接口类*/
@RestController
@RequestMapping("student")
public class StudentController {@Autowiredprivate StudentService studentService;@ResponseBody@GetMapping("/list")public List<Student> getList(){return studentService.list();}@ResponseBody@GetMapping("/{id}")public Student getById(@PathVariable String id){return studentService.getById(id);}@ResponseBody@GetMapping("/page")public Page<Student> getPage(@RequestParam int size, @RequestParam int current){return studentService.page(size, current);}@ResponseBody@PostMapping("/save")public Student save(@RequestBody Student student){return studentService.save(student);}@DeleteMapping("/{id}")public boolean delete(@PathVariable String id){return studentService.delete(id);}
}

• 4.service实现类

package com.learning.cache.service.impl;import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.learning.cache.dao.StudentDao;
import com.learning.cache.entity.Student;
import com.learning.cache.service.StudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cache.annotation.CacheEvict;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Service;import java.util.List;/* @Description 学生服务实现类*/
@Service
public class StudentServiceImpl implements StudentService {@Autowiredprivate StudentDao studentDao;@Cacheable(value={"com:learning:cache:list"})@Overridepublic List<Student> list() {return studentDao.selectList(null);}@Cacheable(value="com:learning:cache:one")@Overridepublic Student getById(String id) {return studentDao.selectById(id);}@Cacheable(value={"com:learning:cache:more"})@Overridepublic Page<Student> page(int size, int current) {Page<Student> page = new Page<>();page.setCurrent(current);page.setSize(size);return studentDao.selectPage(page, null);}@Overridepublic Student save(Student student) {int result = studentDao.insert(student);if(result > 0){return student;}return null;}@CacheEvict(value="com:learning:cache:one", allEntries = true)@Overridepublic boolean delete(String id) {int result = studentDao.deleteById(id);if(result > 0){return true;}return false;}
}

• 5.service接口类

package com.learning.cache.service;import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.learning.cache.entity.Student;import java.util.List;public interface StudentService {List<Student> list();Student getById(String id);Page<Student> page(int size, int current);Student save(Student student);boolean delete(String id);
}

• 6.持久层类

package com.learning.cache.dao;import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.learning.cache.entity.Student;
import org.apache.ibatis.annotations.Mapper;/* @Description 学生持久层类*/
@Mapper
public interface StudentDao extends BaseMapper<Student> {
}

• 7.启动类

package com.learning.cache;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cache.annotation.EnableCaching;
/* @Description 启动类*/
@SpringBootApplication
// 开启启用缓存注解
@EnableCaching
public class Application {public static void main(String[] args) {SpringApplication.run(Application.class, args);}
}

• 8.配置类

package com.learning.cache.config;import com.learning.cache.resolver.CustomCacheResolver;
import org.springframework.cache.interceptor.CacheResolver;
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;/* @Description 自定义Key生成器*/
@Configuration
public class CacheResolverConfig {@Beanpublic RedisCacheManager redisCacheManager(RedisConnectionFactory redisConnectionFactory) {RedisCacheConfiguration cacheConfiguration = RedisCacheConfiguration.defaultCacheConfig().computePrefixWith(cacheName -> cacheName.concat(":"));return RedisCacheManager.builder(redisConnectionFactory).cacheDefaults(cacheConfiguration).build();}@Bean("customCacheResolver")public CacheResolver customCacheResolver(RedisConnectionFactory redisConnectionFactory) {return new CustomCacheResolver(redisCacheManager(redisConnectionFactory));}
}

package com.learning.cache.config;import org.apache.ibatis.executor.Executor;
import org.apache.ibatis.mapping.MappedStatement;
import org.springframework.cache.interceptor.KeyGenerator;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;import java.lang.reflect.Method;
import java.util.Arrays;
import java.util.UUID;/* @Description 自定义Key生成器*/
@Configuration
public class KeyGeneratorConfig {@Bean("customKeyGenerator")public KeyGenerator keyGenerator(){return new KeyGenerator() {@Overridepublic Object generate(Object o, Method method, Object... objects) {return method.getName() + Arrays.asList(objects).toString() + UUID.randomUUID();}};}
}

package com.learning.cache.config;import com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor;
import com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;/* @Description 分页配置类*/
@Configuration
public class MybatisPlusConfig {@Beanpublic MybatisPlusInterceptor mybatisPlusInterceptor(){MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();interceptor.addInnerInterceptor(new PaginationInnerInterceptor());return interceptor;}
}

package com.learning.cache.resolver;import lombok.extern.slf4j.Slf4j;
import org.springframework.cache.Cache;
import org.springframework.cache.CacheManager;
import org.springframework.cache.interceptor.*;
import org.springframework.context.expression.MethodBasedEvaluationContext;
import org.springframework.core.DefaultParameterNameDiscoverer;
import org.springframework.core.ParameterNameDiscoverer;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.Expression;
import org.springframework.expression.spel.standard.SpelExpressionParser;import java.lang.reflect.Method;
import java.util.Collection;/* @Description 自定义缓存解析器*/
@Slf4j
public class CustomCacheResolver extends SimpleCacheResolver {public CustomCacheResolver(CacheManager cacheManager) {super(cacheManager);}@Overridepublic Collection<? extends Cache> resolveCaches(CacheOperationInvocationContext<?> context) {// 拿到缓存Collection<? extends Cache> caches = super.resolveCaches(context);Object target = context.getTarget();BasicOperation operation = context.getOperation();Method method = context.getMethod();Object[] args = context.getArgs();ParameterNameDiscoverer paramNameDiscoverer = new DefaultParameterNameDiscoverer();EvaluationContext evaluationContext = new MethodBasedEvaluationContext(context.getOperation(), context.getMethod(), context.getArgs(), paramNameDiscoverer);Expression expression = (new SpelExpressionParser()).parseExpression(((CacheableOperation) context.getOperation()).getKey());// 获取所有的缓存的名字context.getOperation().getCacheNames().forEach(cacheName -> {log.info("缓存的name:{}", cacheName);String key = cacheName + ':' + expression.getValue(evaluationContext, String.class);log.info("缓存的key全路径：{}", key);});// 返回缓存return caches;}
}

2.2 value属性与cacheNames属性

2.2.1 单个缓存代码示例

package com.learning.cache.service.impl;import com.learning.cache.dao.StudentDao;
import com.learning.cache.entity.Student;
import com.learning.cache.service.StudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Service;import java.util.List;/* @Description 学生服务实现类*/
@Service
public class StudentServiceImpl implements StudentService {@Autowiredprivate StudentDao studentDao;// com:learning:cache会作为redis的key的一部分@Cacheable(value="com:learning:cache:list")@Overridepublic List<Student> list() {return studentDao.selectList(null);}
}

2.2.2 单个缓存效果截图

2.2.3 多个缓存代码示例

package com.learning.cache.service.impl;import com.learning.cache.dao.StudentDao;
import com.learning.cache.entity.Student;
import com.learning.cache.service.StudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Service;import java.util.List;/* @Description 学生服务实现类*/
@Service
public class StudentServiceImpl implements StudentService {@Autowiredprivate StudentDao studentDao;// 多个值，会将方法的返回结果存入到不同的缓存key中@Cacheable(value={"com:learning:cache:list","cn:learning:cache:list"})@Overridepublic List<Student> list() {return studentDao.selectList(null);}
}

2.2.4 多个缓存效果截图

2.3 key属性

2.3.1 方法没有参数示例

package com.learning.cache.service.impl;import com.learning.cache.dao.StudentDao;
import com.learning.cache.entity.Student;
import com.learning.cache.service.StudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Service;import java.util.List;/* @Description 学生服务实现类*/
@Service
public class StudentServiceImpl implements StudentService {@Autowiredprivate StudentDao studentDao;@Cacheable(value={"com:learning:cache:list"})@Overridepublic List<Student> list() {return studentDao.selectList(null);}
}

2.3.2 方法没有参数截图

2.3.3 方法有一个参数示例

package com.learning.cache.service.impl;import com.learning.cache.dao.StudentDao;
import com.learning.cache.entity.Student;
import com.learning.cache.service.StudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Service;import java.util.List;/* @Description 学生服务实现类*/
@Service
public class StudentServiceImpl implements StudentService {@Autowiredprivate StudentDao studentDao;// String id 一个参数的key情况@Cacheable(value={"com:learning:cache:one"})@Overridepublic Student getById(String id) {return studentDao.selectById(id);}
}

2.3.4 方法有一个参数截图

2.3.5 方法有多个参数示例

package com.learning.cache.service.impl;import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.learning.cache.dao.StudentDao;
import com.learning.cache.entity.Student;
import com.learning.cache.service.StudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Service;import java.util.List;/* @Description 学生服务实现类*/
@Service
public class StudentServiceImpl implements StudentService {@Autowiredprivate StudentDao studentDao;@Cacheable(value={"com:learning:cache:more"})@Overridepublic Page<Student> page(int size, int current) {Page<Student> page = new Page<>();page.setCurrent(current);page.setSize(size);return studentDao.selectPage(page, null);}
}

2.3.6 方法有多个参数截图

2.3.7 指定key（从参数中指定）

package com.learning.cache.service.impl;import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.learning.cache.dao.StudentDao;
import com.learning.cache.entity.Student;
import com.learning.cache.service.StudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Service;import java.util.List;/* @Description 学生服务实现类*/
@Service
public class StudentServiceImpl implements StudentService {@Autowiredprivate StudentDao studentDao;@Cacheable(value="com:learning:cache:one", key="#id")@Overridepublic Student getById(String id) {return studentDao.selectById(id);}
}

2.3.8 指定key截图

2.4 keyGenerator属性

2.4.1 自定义key生成器代码示例

package com.learning.cache.service.impl;import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.learning.cache.dao.StudentDao;
import com.learning.cache.entity.Student;
import com.learning.cache.service.StudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Service;import java.util.List;/* @Description 学生服务实现类*/
@Service
public class StudentServiceImpl implements StudentService {@Autowiredprivate StudentDao studentDao;@Cacheable(value="com:learning:cache:one", keyGenerator="customKeyGenerator")@Overridepublic Student getById(String id) {return studentDao.selectById(id);}  
}

package com.learning.cache.config;import org.apache.ibatis.executor.Executor;
import org.apache.ibatis.mapping.MappedStatement;
import org.springframework.cache.interceptor.KeyGenerator;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;import java.lang.reflect.Method;
import java.sql.Statement;
import java.util.Arrays;
import java.util.UUID;/* @Description 自定义Key生成器*/
@Configuration
public class KeyGeneratorConfig {@Bean("customKeyGenerator")public KeyGenerator keyGenerator(){return new KeyGenerator() {@Overridepublic Object generate(Object o, Method method, Object... objects) {return method.getName() + Arrays.asList(objects).toString() + UUID.randomUUID();}};}
}

2.4.2 自定义key生成器截图

2.5 cacheResolver属性

2.5.1 自定义cacheResolver缓存解析器代码示例

package com.learning.cache.service.impl;import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.learning.cache.dao.StudentDao;
import com.learning.cache.entity.Student;
import com.learning.cache.service.StudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Service;import java.util.List;/* @Description 学生服务实现类*/
@Service
public class StudentServiceImpl implements StudentService {@Autowiredprivate StudentDao studentDao;@Cacheable(value="com:learning:cache:one",key="#id", cacheResolver="customCacheResolver")@Overridepublic Student getById(String id) {return studentDao.selectById(id);}
}

package com.learning.cache.resolver;import lombok.extern.slf4j.Slf4j;
import org.springframework.cache.Cache;
import org.springframework.cache.CacheManager;
import org.springframework.cache.interceptor.*;
import org.springframework.context.expression.MethodBasedEvaluationContext;
import org.springframework.core.DefaultParameterNameDiscoverer;
import org.springframework.core.ParameterNameDiscoverer;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.Expression;
import org.springframework.expression.spel.standard.SpelExpressionParser;import java.lang.reflect.Method;
import java.util.Collection;/* @Description 自定义缓存解析器*/
@Slf4j
public class CustomCacheResolver extends SimpleCacheResolver {public CustomCacheResolver(CacheManager cacheManager) {super(cacheManager);}@Overridepublic Collection<? extends Cache> resolveCaches(CacheOperationInvocationContext<?> context) {// 拿到缓存Collection<? extends Cache> caches = super.resolveCaches(context);Object target = context.getTarget();BasicOperation operation = context.getOperation();Method method = context.getMethod();Object[] args = context.getArgs();ParameterNameDiscoverer paramNameDiscoverer = new DefaultParameterNameDiscoverer();EvaluationContext evaluationContext = new MethodBasedEvaluationContext(context.getOperation(), context.getMethod(), context.getArgs(), paramNameDiscoverer);Expression expression = (new SpelExpressionParser()).parseExpression(((CacheableOperation) context.getOperation()).getKey());// 获取所有的缓存的名字context.getOperation().getCacheNames().forEach(cacheName -> {log.info("缓存的name:{}", cacheName);String key = cacheName + ':' + expression.getValue(evaluationContext, String.class);log.info("缓存的key全路径：{}", key);});// 返回缓存return caches;}
}

2.5.2 自定义cacheResolver缓存解析器截图

2.6 condition属性

2.6.1 指定条件进行缓存代码示例

package com.learning.cache.service.impl;import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.learning.cache.dao.StudentDao;
import com.learning.cache.entity.Student;
import com.learning.cache.service.StudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Service;import java.util.List;/* @Description 学生服务实现类*/
@Service
public class StudentServiceImpl implements StudentService {@Autowiredprivate StudentDao studentDao;// 指定id为1的可以缓存@Cacheable(value="com:learning:cache:one", condition = "#id eq '1'")@Overridepublic Student getById(String id) {return studentDao.selectById(id);}
}

2.6.2 指定条件进行缓存截图

2.7 unless属性

2.7.1 指定条件不进行缓存代码示例

package com.learning.cache.service.impl;import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.learning.cache.dao.StudentDao;
import com.learning.cache.entity.Student;
import com.learning.cache.service.StudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Service;import java.util.List;/* @Description 学生服务实现类*/
@Service
public class StudentServiceImpl implements StudentService {@Autowiredprivate StudentDao studentDao;// 对查询结果为null的不做缓存，去掉的话会缓存空值@Cacheable(value="com:learning:cache:one", unless = "#result == null")@Overridepublic Student getById(String id) {return studentDao.selectById(id);}
}

2.7.2 结果为null的缓存截图

2.8 allEntries属性

2.8.1 清除全部缓存代码示例

package com.learning.cache.service.impl;import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.learning.cache.dao.StudentDao;
import com.learning.cache.entity.Student;
import com.learning.cache.service.StudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cache.annotation.CacheEvict;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Service;import java.util.List;/* @Description 学生服务实现类*/
@Service
public class StudentServiceImpl implements StudentService {@Autowiredprivate StudentDao studentDao;@Cacheable(value="com:learning:cache:one")@Overridepublic Student getById(String id) {return studentDao.selectById(id);}@CacheEvict(value="com:learning:cache:one", allEntries = true)@Overridepublic boolean delete(String id) {int result = studentDao.deleteById(id);if(result > 0){return true;}return false;}
}

2.8.2 先查2次缓存起来，然后删除1条，清除所有截图