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SpringBoot 缓存管理器CacheManager

        从3.1开始Spring定义了org.springframework.cache.Cache和org.springframework.cache.CacheManager接口来统一不同的缓存技术；并支持使用JCache（JSR-107） 注解简化开发.

• Cache接口为缓存的组件规范定义，包含缓存的各种操作集合；
• Cache接口下Spring提供了各种xxxCache的实现；如RedisCache，EhCacheCache ,ConcurrentMapCache等；

快速开始

1、导入Maven

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

<!-- redis -->
<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>
<dependency>
	<groupId>org.apache.commons</groupId>
	<artifactId>commons-pool2</artifactId>
</dependency>

        因为需要用RedisCacheManager 所以导入Redis依赖

2、配置Redis并开启缓存支持

import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.PropertyAccessor;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.cache.CacheManager;
import org.springframework.cache.annotation.CachingConfigurerSupport;
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.cache.RedisCacheManager;
import org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.serializer.Jackson2JsonRedisSerializer;
import org.springframework.data.redis.serializer.RedisSerializationContext;
import org.springframework.data.redis.serializer.RedisSerializer;
import org.springframework.data.redis.serializer.StringRedisSerializer;

import javax.annotation.Resource;
import java.time.Duration;

/**
 * 
 * @author rstyro
 * @time 2018-07-31
 *
 */
@Configuration
@EnableCaching // 开启缓存支持
public class RedisConfig extends CachingConfigurerSupport {
    @Resource
    private LettuceConnectionFactory lettuceConnectionFactory;


    /**
     * 配置CacheManager
     * @return
     */
    @Bean
    public CacheManager cacheManager() {
        RedisSerializer<String> redisSerializer = new StringRedisSerializer();
        Jackson2JsonRedisSerializer jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer(Object.class);

        //解决查询缓存转换异常的问题
        ObjectMapper om = new ObjectMapper();
        om.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);
        om.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
        jackson2JsonRedisSerializer.setObjectMapper(om);

        // 配置序列化（解决乱码的问题）
        RedisCacheConfiguration config = RedisCacheConfiguration.defaultCacheConfig()
//                .entryTtl(Duration.ZERO)
                .entryTtl(Duration.ofSeconds(20))   //设置缓存失效时间
                .serializeKeysWith(RedisSerializationContext.SerializationPair.fromSerializer(redisSerializer))
                .serializeValuesWith(RedisSerializationContext.SerializationPair.fromSerializer(jackson2JsonRedisSerializer))
                .disableCachingNullValues();

        RedisCacheManager cacheManager = RedisCacheManager.builder(lettuceConnectionFactory)
                .cacheDefaults(config)
                .build();
        return cacheManager;
    }


    /**
     * RedisTemplate配置
     */
    @Bean
    public RedisTemplate<String, Object> redisTemplate(LettuceConnectionFactory lettuceConnectionFactory) {
        // 设置序列化
        Jackson2JsonRedisSerializer<Object> jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer<Object>(
                Object.class);
        ObjectMapper om = new ObjectMapper();
        om.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);
        om.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
        jackson2JsonRedisSerializer.setObjectMapper(om);
        // 配置redisTemplate
        RedisTemplate<String, Object> redisTemplate = new RedisTemplate<String, Object>();
        redisTemplate.setConnectionFactory(lettuceConnectionFactory);
        RedisSerializer<?> stringSerializer = new StringRedisSerializer();
        redisTemplate.setKeySerializer(stringSerializer);// key序列化
        redisTemplate.setValueSerializer(jackson2JsonRedisSerializer);// value序列化
        redisTemplate.setHashKeySerializer(stringSerializer);// Hash key序列化
        redisTemplate.setHashValueSerializer(jackson2JsonRedisSerializer);// Hash value序列化
        redisTemplate.afterPropertiesSet();
        return redisTemplate;
    }


}

缓存工作原理

        当我们引入缓存的时候，SpringBoot的缓存自动配置CacheAutoConfiguration就会生效

• 在CacheAutoConfiguration 中的CacheConfigurationImportSelector会导入很多缓存组件配置类

• 通过debug看源码,知道imports 的内容如下

  static class CacheConfigurationImportSelector implements ImportSelector { CacheConfigurationImportSelector() { } public String[] selectImports(AnnotationMetadata importingClassMetadata) { CacheType[] types = CacheType.values(); String[] imports = new String[types.length]; for(int i = 0; i < types.length; ++i) { imports[i] = CacheConfigurations.getConfigurationClass(types[i]); } return imports; } } /** imports 如下 0 = "org.springframework.boot.autoconfigure.cache.GenericCacheConfiguration" 1 = "org.springframework.boot.autoconfigure.cache.JCacheCacheConfiguration" 2 = "org.springframework.boot.autoconfigure.cache.EhCacheCacheConfiguration" 3 = "org.springframework.boot.autoconfigure.cache.HazelcastCacheConfiguration" 4 = "org.springframework.boot.autoconfigure.cache.InfinispanCacheConfiguration" 5 = "org.springframework.boot.autoconfigure.cache.CouchbaseCacheConfiguration" 6 = "org.springframework.boot.autoconfigure.cache.RedisCacheConfiguration" 7 = "org.springframework.boot.autoconfigure.cache.CaffeineCacheConfiguration" 8 = "org.springframework.boot.autoconfigure.cache.SimpleCacheConfiguration" 9 = "org.springframework.boot.autoconfigure.cache.NoOpCacheConfiguration" */

• 如果没有引Redis， 则SimpleCacheConfiguration这个就是默认的配置类

• 在SimpleCacheConfiguration注入了一个ConcurrentMapCacheManager

• ConcurrentMapCacheManager 实现了CacheManager 接口

• ConcurrentMapCacheManager 通过 ConcurrentHashMap 把数据缓存起来

• 在 CacheManager 有一个Cache getCache(String var1) 方法换取缓存

• 流程大概就这里，感兴趣的同学可以打断点阅读源码

代码示例地址

• Github: https://github.com/rstyro/Springboot/tree/master/SpringBoot-RedisCacheManager
• Gitee : spring-boot: springboot 和一些主流框架的整合的各个基本demo - Gitee.com

例子2

1、向pom文件中添加依赖

     <!--springboot中的redis依赖-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-redis</artifactId>
        </dependency>

2、application.yml添加配置

spring:
  redis:
    host: localhost     # Redis服务器地址
    database: 0         # Redis数据库索引（默认为0）
    port: 6379          # Redis服务器连接端口
    password: ld123456  # Redis服务器连接密码（默认为空）

3、RedisConfig配置类

package com.donleo.mybatis.config;

import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.PropertyAccessor;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.cache.CacheManager;
import org.springframework.cache.annotation.CachingConfigurerSupport;
import org.springframework.cache.annotation.EnableCaching;
import org.springframework.cache.interceptor.KeyGenerator;
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;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.serializer.Jackson2JsonRedisSerializer;
import org.springframework.data.redis.serializer.RedisSerializationContext;
import org.springframework.data.redis.serializer.RedisSerializer;
import org.springframework.data.redis.serializer.StringRedisSerializer;

import java.util.Arrays;

/**
 * @author liangd
 * date 2020-12-04 16:15
 * code Redis配置类
 */
@Configuration
@EnableCaching
public class RedisConfig extends CachingConfigurerSupport {
    /**
     * 配置redisTemplate 代替默认配置
     * @param redisConnectionFactory  RedisConnectionFactory
     * @return  RedisTemplate
     */
    @Bean
    public RedisTemplate<String, Object> redisTemplate(RedisConnectionFactory redisConnectionFactory) {
        RedisTemplate<String, Object> template = new RedisTemplate<>();
        template.setConnectionFactory(redisConnectionFactory);
        Jackson2JsonRedisSerializer serializer = new Jackson2JsonRedisSerializer(Object.class);
        ObjectMapper mapper = new ObjectMapper();
        mapper.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);
        mapper.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
        serializer.setObjectMapper(mapper);

        template.setValueSerializer(serializer);
        //使用StringRedisSerializer来序列化和反序列化redis的key值
        template.setKeySerializer(new StringRedisSerializer());
        template.afterPropertiesSet();
        return template;
    }

    /**
     *
     * 配置 cacheManager 代替默认的cacheManager （缓存管理器）
     * @param factory RedisConnectionFactory
     * @return  CacheManager
     */
    @Bean
    public CacheManager cacheManager(RedisConnectionFactory factory) {
        RedisSerializer<String> redisSerializer = new StringRedisSerializer();
        Jackson2JsonRedisSerializer serializer = new Jackson2JsonRedisSerializer(Object.class);
        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);
        objectMapper.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
        serializer.setObjectMapper(objectMapper);
        // 配置序列化
        RedisCacheConfiguration config = RedisCacheConfiguration.defaultCacheConfig()
                .serializeKeysWith(RedisSerializationContext.SerializationPair.fromSerializer(redisSerializer))
                .serializeValuesWith(RedisSerializationContext.SerializationPair.fromSerializer(serializer));

        RedisCacheManager cacheManager = RedisCacheManager.builder(factory)
                .cacheDefaults(config)
                .build();
        return cacheManager;
    }

    /**
     * 配置KeyGenerator
     * @return
     */
    @Bean
    @Override
    public KeyGenerator keyGenerator() {
        //lambda 表达式
        return (target, method, params) -> method.getName() + Arrays.asList(params);
    }
    /*
        // 1. 不需要参数,返回值为 5
            () -> 5

        // 2. 接收一个参数(数字类型),返回其2倍的值
            x -> 2 * x

        // 3. 接受2个参数(数字),并返回他们的差值
            (x, y) -> x – y

        // 4. 接收2个int型整数,返回他们的和
            (int x, int y) -> x + y

        // 5. 接受一个 string 对象,并在控制台打印,不返回任何值(看起来像是返回void)
            (String s) -> System.out.print(s)
     */
     /*   @Bean
       @Override
       public KeyGenerator keyGenerator() {
           return (target,  method,  params)->{
               return method.getName()+ Arrays.asList(params);
           };
       }*/
}

KeyGenerator

/**
* 生产key的策略
* @return
*/
@Bean
public KeyGenerator wiselyKeyGenerator() {
    return new KeyGenerator() {
        @Override
        public Object generate(Object target, Method method, Object... params) {
                StringBuilder sb = new StringBuilder();
                sb.append(target.getClass().getName());
                sb.append(method.getName());
                for (Object obj : params) {
                    sb.append(obj.toString());
                }
                return sb.toString();
        }
     };
}

例子3

        针对基于Redis API的RedisTemplate进行了自定义序列化机制的改进，从而实现了相对熟悉的JSON格式缓存数据，但是这种自定义的RedisTemplate对于基于注解的Redis缓存实现来说，是没有作用的，读者可以自行演示。接下来，针对基于注解的Redis缓存机制和自定义序列化方式的实现进行讲解。

1．Redis注解默认序列化机制

        打开Spring Boot整合Redis组件提供的缓存自动配置类RedisCacheConfiguration（org.springframework.boot.autoconfigure.cache包下的），查看该类的源码信息，其核心代码如下。

@Configuration
class RedisCacheConfiguration {
    @Bean
    public RedisCacheManager cacheManager(RedisConnectionFactory
                                    redisConnectionFactory,ResourceLoader resourceLoader) {
        RedisCacheManagerBuilder builder =
                      RedisCacheManager.builder(redisConnectionFactory)
         .cacheDefaults(this.determineConfiguration(resourceLoader.getClassLoader()));
        List<String> cacheNames = this.cacheProperties.getCacheNames();
        if(!cacheNames.isEmpty()) {
            builder.initialCacheNames(new LinkedHashSet(cacheNames));
        }
        return (RedisCacheManager)this.customizerInvoker.customize(builder.build());
    }
    private org.springframework.data.redis.cache.RedisCacheConfiguration
 determineConfiguration(ClassLoader classLoader){
        if(this.redisCacheConfiguration != null) {
            return this.redisCacheConfiguration;
        } else {
            Redis redisProperties = this.cacheProperties.getRedis();
            org.springframework.data.redis.cache.RedisCacheConfiguration config =
    org.springframework.data.redis.cache.RedisCacheConfiguration.defaultCacheConfig();
            config = config.serializeValuesWith(SerializationPair.fromSerializer(
                                     new JdkSerializationRedisSerializer(classLoader)));
            ...
            return config;
        }
    }
}

        从上述核心源码中可以看出，同RedisTemplate核心源码类似，RedisCacheConfiguration内部同样通过Redis连接工厂RedisConnectionFactory定义了一个缓存管理器RedisCacheManager；同时定制RedisCacheManager时，也默认使用了JdkSerializationRedisSerializer序列化方式。

        如果想要使用自定义序列化方式的RedisCacheManager进行数据缓存操作，可以参考上述核心代码创建一个名为cacheManager的Bean组件，并在该组件中设置对应的序列化方式即可。

        需要注意的是，本书使用的是Spring Boot 2.X版本进行使用讲解，这与Spring Boot 1.X版本中的一些实现原理并不相同。例如上述RedisCacheManager的构建方式，在Spring Boot 1.X版本中的源码如下。

@Bean
public RedisCacheManager cacheManager(RedisTemplate<Object, Object> redisTemplate) {
    RedisCacheManager cacheManager = new RedisCacheManager(redisTemplate);
    cacheManager.setUsePrefix(true);
    List<String> cacheNames = this.cacheProperties.getCacheNames();
    if(!cacheNames.isEmpty()) {
        cacheManager.setCacheNames(cacheNames);
    }
    return (RedisCacheManager)this.customizerInvoker.customize(cacheManager);
}

        从这两个版本的源码对比可以看出，Spring Boot 1.X版本中，RedisCacheManager是在RedisTemplate的基础上述进行构建的，而Spring Boot 2.X版本中，RedisCacheManager是单独进行构建的。因此，在Spring Boot 2.X版本中，对RedisTemplate进行自定义序列化机制构建后，仍然无法对RedisCacheManager内部默认序列化机制进行覆盖（这也就解释了基于注解的Redis缓存实现仍然会使用JDK默认序列化机制的原因），想要基于注解的Redis缓存实现也使用自定义序列化机制，需要自定义RedisCacheManager。

2．自定义RedisCacheManager

        在chapter06项目的Redis配置类RedisConfig中，按照上一步分析的定制方法自定义名为cacheManager的Bean组件，示例代码如下：

@Bean
public RedisCacheManager cacheManager(RedisConnectionFactory redisConnectionFactory) {
    // 分别创建String和JSON格式序列化对象，对缓存数据key和value进行转换
    RedisSerializer<String> strSerializer = new StringRedisSerializer();
    Jackson2JsonRedisSerializer jacksonSeial = 
new Jackson2JsonRedisSerializer(Object.class);
    // 解决查询缓存转换异常的问题
    ObjectMapper om = new ObjectMapper();
    om.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);
    om.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
    jacksonSeial.setObjectMapper(om);
    // 定制缓存数据序列化方式及时效
    RedisCacheConfiguration config = RedisCacheConfiguration.defaultCacheConfig()
            .entryTtl(Duration.ofDays(1))
             .serializeKeysWith(RedisSerializationContext.SerializationPair
                                  .fromSerializer(strSerializer))                      
            .serializeValuesWith(RedisSerializationContext.SerializationPair
                                  .fromSerializer(jacksonSeial))
            .disableCachingNullValues();
    RedisCacheManager cacheManager = RedisCacheManager
                    .builder(redisConnectionFactory).cacheDefaults(config).build();
    return cacheManager;
}

        上述代码中，在RedisConfig配置类中使用@Bean注解注入了一个默认名称为方法名的cacheManager组件。在定义的Bean组件中，通过RedisCacheConfiguration对缓存数据的key和value分别进行了序列化方式的定制，其中缓存数据的key定制为StringRedisSerializer（即String格式），而value定制为了Jackson2JsonRedisSerializer（即JSON格式），同时还使用entryTtl(Duration.ofDays(1))方法将缓存数据有效期设置为1天。

参考：

SpringBoot与RedisCacheManager整合 | 帅大叔的博客

自定义RedisCacheManager - java学习教程_ java培训机构_java编程思想_java核心技术