055 SpringCache

缓存一致性

锁
设置过期时间

读写锁
设置过期时间

Spring Cache

1.读模式
缓存穿透：查询一个null数据，解决：开启缓存空数据，spring.cache.redis.cache-null-values=true
缓存击穿：大量并发进来查询一个正好过期的数据，解决：加锁
缓存雪崩：大量的key同时过期 解决：加过期时间，spring.cache.redis.time-to-live=3600000
2.写模式：缓存与数据库一致
读写加锁。
引入Canal，感知到MySQL的更新去更新数据库
读多写多，直接去数据库查询就行

pom.xml

        <!-- https://mvnrepository.com/artifact/org.springframework.session/spring-session-data-redis -->
        <dependency>
            <groupId>org.springframework.session</groupId>
            <artifactId>spring-session-data-redis</artifactId>

        </dependency>


        <!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-starter-cache -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-cache</artifactId>
        </dependency>

application.yml

spring:
  cache:
    type: redis
    redis:
      time-to-live: 3600000
      cache-null-values: true

CubemallProductApplication.java

package com.xd.cubemall.product;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cache.annotation.EnableCaching;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.openfeign.EnableFeignClients;

@EnableCaching
@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients(basePackages = "com.xd.cubemall.product.feign")
public class CubemallProductApplication {

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

}

SpringCache改造三级分类

    /**
     * 使用SpringCache改造三级分类
     * @return
     */
    @Cacheable(value={"category"}, key = "#root.method.name")
    public List<CategoryVo> getLevel1Categorys() {


            System.out.println("缓存不命中，查询数据库。。。");
            //2.缓存中没有数据，查询数据库，从数据库查询分类数据
            List<CategoryVo> categoryJsonFromDb = getCategoryJsonFromWithRedissonLock();

            return categoryJsonFromDb;





    }

MyCacheConfig.java

package com.xd.cubemall.product.config;


import org.springframework.boot.autoconfigure.cache.CacheProperties;
import org.springframework.cache.annotation.EnableCaching;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.redis.cache.RedisCacheConfiguration;
import org.springframework.data.redis.serializer.GenericJackson2JsonRedisSerializer;
import org.springframework.data.redis.serializer.RedisSerializationContext;
import org.springframework.data.redis.serializer.StringRedisSerializer;

@Configuration
@EnableCaching
public class MyCacheConfig {

    @Bean
    RedisCacheConfiguration redisCacheConfiguration(CacheProperties cacheProperties){
        RedisCacheConfiguration config = RedisCacheConfiguration.defaultCacheConfig();

        //修改key和value的序列号机制
        config = config.serializeKeysWith(
                RedisSerializationContext.SerializationPair.fromSerializer(new StringRedisSerializer())
        );

        config = config.serializeValuesWith(
                RedisSerializationContext.SerializationPair.fromSerializer(new GenericJackson2JsonRedisSerializer())

        );



        //将配置文件中的所有配置进行生效
        CacheProperties.Redis redisProperties = cacheProperties.getRedis();
        if (redisProperties.getTimeToLive() != null) {
            config = config.entryTtl(redisProperties.getTimeToLive());
        }

        if (redisProperties.getKeyPrefix() != null) {
            config = config.prefixKeysWith(redisProperties.getKeyPrefix());
        }

        if (!redisProperties.isCacheNullValues()) {
            config = config.disableCachingNullValues();
        }


        if (!redisProperties.isUseKeyPrefix()) {
            config = config.disableKeyPrefix();
        }

        return config;

    }
}

缓存一致性

    /**
     * 三级菜单的级联更新 (缓存一致性)
     * @param category
     */
    @CacheEvict(value = "category", key = "'getLevel1Categorys'")
    @Override
    public void updateCascade(CategoryEntity category) {
        this.updateById(category);
    }