[Java知识库]Spring Cache 总结

1、配置

1、依赖

<!--springcache依赖-->
   <dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-cache</artifactId>
   </dependency>
   
<!--使用redis作为缓存-->
   <dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-data-redis</artifactId>
   </dependency>

2、yml配置

spring:
  cache:
    type: redis #指定缓存类型为redis
 # redis配置
  redis:
    host: localhost
    port: 6379
    database: 2
    jedis:
      pool:
        max-active: -1
        max-wait: 3000ms
    timeout: 3000ms

3、cache配置

package com.example.demo.config;
import org.springframework.cache.annotation.EnableCaching;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.redis.cache.RedisCacheManager;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.data.redis.serializer.StringRedisSerializer;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.beans.factory.support.AbstractBeanDefinition;
import org.springframework.cache.CacheManager;
import org.springframework.cache.interceptor.CacheOperation;
import org.springframework.cache.interceptor.CacheOperationSource;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.data.redis.cache.RedisCacheConfiguration;
import org.springframework.data.redis.serializer.GenericJackson2JsonRedisSerializer;
import org.springframework.data.redis.serializer.RedisSerializationContext;
import org.springframework.util.*;

import java.time.Duration;
import java.util.*;

@EnableCaching
@Configuration
public class SpringCacheConfig implements ApplicationContextAware {


	private Set<String> cacheNames = new HashSet<>();

	private static final String SEPARATOR = "#";

	@Bean
	public CacheManager cacheManager(RedisConnectionFactory connectionFactory) {
		//默认过期时间2天
		RedisCacheConfiguration defaultConfiguration = getRedisCacheConfigurationWithTtl(2 * 24 * 3600);
		RedisCacheManager.RedisCacheManagerBuilder builder = RedisCacheManager
				.builder(connectionFactory)
				.cacheDefaults(defaultConfiguration);
		if (!CollectionUtils.isEmpty(cacheNames)) {
			Map<String, RedisCacheConfiguration> cacheConfigurations = new LinkedHashMap<>();
			for (String cacheName : cacheNames) {
				if (cacheName.contains(SEPARATOR)) {
					String[] strs = StringUtils.split(cacheName, SEPARATOR);
					Assert.notNull(strs);
					long ttl = Long.parseLong(strs[1].trim());
					RedisCacheConfiguration customizedConfiguration = getRedisCacheConfigurationWithTtl(ttl);
					cacheConfigurations.put(cacheName, customizedConfiguration);
				}
			}
			if (cacheConfigurations.size() > 0) {
				builder.withInitialCacheConfigurations(cacheConfigurations);
			}
		}
		return builder.build();

	}

	private RedisCacheConfiguration getRedisCacheConfigurationWithTtl(long ttl) {
		return RedisCacheConfiguration
				.defaultCacheConfig()
				.disableCachingNullValues()
				.serializeKeysWith(RedisSerializationContext.SerializationPair.fromSerializer(new StringRedisSerializer()))
				.serializeValuesWith(RedisSerializationContext.SerializationPair.fromSerializer(new GenericJackson2JsonRedisSerializer()))
				.entryTtl(Duration.ofSeconds(ttl));
	}

	//实现ApplicationContextAware接口的Bean会被提前实例化，这个方法会优先执行
	@Override
	public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
		if (!(applicationContext instanceof ConfigurableApplicationContext)) {
			return;
		}
		ConfigurableApplicationContext context = (ConfigurableApplicationContext) applicationContext;
		//CacheOperationSource 可以被提前实例化，是spring cache提供的工具类
		CacheOperationSource cacheOperationSource = context.getBean(CacheOperationSource.class);
		ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
		for (String beanName : beanFactory.getBeanDefinitionNames()) {
			AbstractBeanDefinition beanDefinition = (AbstractBeanDefinition) beanFactory.getBeanDefinition(beanName);
			try {
				Class<?> beanClass = beanDefinition.resolveBeanClass(ClassUtils.getDefaultClassLoader());
				if (beanClass != null) {
					ReflectionUtils.doWithMethods(beanClass, m -> {
								Collection<CacheOperation> cacheOperations = cacheOperationSource.getCacheOperations(m, beanClass);
								if (!CollectionUtils.isEmpty(cacheOperations)) {
									for (CacheOperation operation : cacheOperations) {
										cacheNames.addAll(operation.getCacheNames());
									}
								}
							}
					);
				}
			} catch (ClassNotFoundException e) {
				e.printStackTrace();
			}
		}
	}
}

2、注解

@EnableCaching （开启缓存功能）

开启缓存，缓存才能生效
直接启动类上开启

@Cacheable （将数据保存到缓存）

根据方法返回结果进行缓存，下次请求时，如果缓存存在，则直接读取缓存数据返回；如果缓存不存在，则执行方法，并把返回的结果存入缓存中。一般用在查询方法上。

拥有属性：

1、key参数设置，SpringEl表达式

测试
1、默认方法

默认方法解析：

• 如果缓存中有，方法不用调用
• key默认自动生成，缓存名字::SimpleKey []

value就是方法的返回值

2、指定简单key
key = "'cacheableKey'"

指定key,默认是spEL表达式，所以字符串需要用单引号

	@Cacheable(value = {"cacheable1","cacheable2"},key = "'cacheableKey'")

3、使用参数作为key

key = "#name"

此时的key就是code的值

或者拼接字符串

// 或者拼接一下
@Cacheable(value = {"cacheable1"},key = "#name + ':' + #code")

4、使用实体类里的参数
key = "#user.username"

5、更多key方法

2、其他参数示例

cacheNames和value作用一样，分区（文件夹）

@Cacheable(cacheNames = {"cacheable1"},key = "#user")

unless条件符合不缓存, 如下：结果是null，不用缓存

@Cacheable(value = {"cacheable1"},key = "#code",unless = "#result == null" )

condition条件符合缓存, 如下：参数user的长度大于2，可以缓存

@Cacheable(value = {"cacheable1"},key = "#user",condition = "#user.length() > 2")

keyGenerator 生成key

@Cacheable(cacheNames = {"cacheable1"},keyGenerator ="keyGenerator" )

这个需要自己写生成的算法，keyGenerator =”方法名“

@Component
public class keyGenerator implements KeyGenerator {
	@Override
	public Object generate(Object o, Method method, Object... objects) {
		// 这里写你的key生成的算法
		return "123";
	}
}

@CacheEvict (将数据从缓存删除)

使用该注解标志的方法，会清空指定的缓存。一般用在更新或者删除方法上

拥有属性：

@CacheEvict(value = {"cacheable1"},key ="'123'",allEntries = true,beforeInvocation = true)

@CachePut (不影响方法执行更新缓存)

使用该注解标志的方法，每次都会执行，并将结果存入指定的缓存中，会更新缓存的值。其他方法可以直接从响应的缓存中读取缓存数据，而不需要再去查询数据库。一般用在新增方法上。

拥有属性：

@CachePut(value = {"cacheable1"},key ="'123'")

@Caching （组合多个缓存操作）

该注解可以实现同一个方法上同时使用多种注解。各属性值可以多个，如删除多个key

拥有属性：

@Caching(evict = {@CacheEvict(value = "caching",key = "'123'"),@CacheEvict(value = "caching2",key = "'321'")},
		cacheable = @Cacheable(value = "caching",key = "'123'"),
		put = @CachePut(value = "caching2",key = "'321'"))

@CacheConfig (在类级别共享缓存的相同配置)

当我们需要缓存的地方越来越多，你可以使用@CacheConfig(cacheNames = {“cacheName”})注解在 class 之上来统一指定value的值，这时可省略value，如果你在你的方法依旧写上了value，那么依然以方法的value值为准。

拥有属性：

@CacheConfig(cacheNames = {"cacheName"})

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