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Spring缓存使用

缓存注解

对于Spring，缓存组件例如EhCache是可拔插的，而缓存注解是通用的。

@Cacheable

标记在方法或者类上，标识该方法或类支持缓存。Spring调用注解标识方法后会将返回值缓存到redis，以保证下次同条件调用该方法时直接从缓存中获取返回值。这样就不需要再重新执行该方法的业务处理过程，提高效率。
@Cacheable常用的三个参数如下：
cacheNames 缓存名称
key 缓存的key，需要注意key的写法哈
condition 缓存执行的条件，返回true时候执行
cacheManager 使用的cacheManager的bean名称
sync 如果多个请求同时来访问同一个key的数据，则sync表示加锁同步，等第一个请求返回数据后，其他请求直接获取缓存里的数据。

@Cacheable(value = "DICT", key = "'getDictById'+#id", sync = true)

@CachePut

标记在方法或者类上，标识该方法或类支持缓存。每次都会执行目标方法，并将执行结果以键值对的形式存入指定的缓存中。

@CachePut(value = "DICT", key = "'getDictById'+#model.getId()")

@CacheEvict

@CacheEvict是用来标注在需要清除缓存元素的方法或类上的。@CacheEvict可以指定的属性有value、key、condition、allEntries和beforeInvocation。其中value、key和condition的语义与@Cacheable对应的属性类似。即
value表示清除操作是发生在哪些Cache上的（对应Cache的名称）；
key表示需要清除的是哪个key，如未指定则会使用默认策略生成的key；
condition表示清除操作发生的条件。
allEntries是boolean类型，表示是否需要清除缓存中的所有元素。默认为false，表示不需要。当指定了allEntries为true时，Spring Cache将忽略指定的key。
beforeInvocation 清除操作默认是在对应方法成功执行之后触发的，即方法如果因为抛出异常而未能成功返回时也不会触发清除操作。当我们指定该属性值为true时，Spring会在调用该方法之前清除缓存中的指定元素。

@CacheEvict(value = "DICT",key = "'getDictById'+#model.getId()",beforeInvocation=false)

使用Ehcache作为缓存

pom坐标

  <dependency><groupId>net.sf.ehcache</groupId><artifactId>ehcache</artifactId><version>2.8.3</version></dependency><!-- Ehcache依赖此组件创建bean --><dependency><groupId>org.springframework</groupId><artifactId>spring-context-support</artifactId><version>5.1.5.RELEASE</version></dependency>

ehcache.xml 配置文件

<?xml version="1.0" encoding="UTF-8"?>
<ehcache xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:noNamespaceSchemaLocation="http://ehcache.org/ehcache.xsd"updateCheck="false"><diskStore path="java.io.tmpdir/Tmp_EhCache" /><!-- defaultCache，是默认的缓存策略 --><!-- 如果你指定的缓存策略没有找到，那么就用这个默认的缓存策略 --><!-- external：缓存对象是否一直存在，如果设置为true的话，那么timeout就没有效果，缓存就会一直存在，一般默认就是false --><!-- maxElementsInMemory：内存中可以缓存多少个缓存条目 --><!-- overflowToDisk：如果内存不够的时候，是否溢出到磁盘 --><!-- diskPersistent：是否启用磁盘持久化的机制，在jvm崩溃的时候和重启之间 --><!-- timeToIdleSeconds：对象最大的闲置的时间，如果超出闲置的时间，可能就会过期  单位：秒 当eternal=false对象不是永久有效时使用，可选属性，默认值是0，也就是可闲置时间无穷大--><!-- timeToLiveSeconds：对象最多存活的时间  单位：秒 当eternal=false对象不是永久有效时使用，可选属性，默认值是0，也就是存活时间无穷大--><!-- memoryStoreEvictionPolicy：当缓存数量达到了最大的指定条目数的时候，需要采用一定的算法，从缓存中清除一批数据，LRU，最近最少使用算法，最近一段时间内，最少使用的那些数据，就被干掉了 --><defaultCacheeternal="false"maxElementsInMemory="1000"overflowToDisk="false"diskPersistent="false"timeToIdleSeconds="300"timeToLiveSeconds="600"memoryStoreEvictionPolicy="LRU" /><!-- 手动指定的缓存策略 --><!-- 对不同的数据，缓存策略可以在这里配置多种 --><cachename="local"  eternal="false"maxElementsInMemory="1000"overflowToDisk="false"diskPersistent="false"timeToIdleSeconds="300"timeToLiveSeconds="600"memoryStoreEvictionPolicy="LRU" />    
</ehcache>

EhcacheConfiguration.java

import org.springframework.cache.annotation.EnableCaching;
import org.springframework.cache.ehcache.EhCacheCacheManager;
import org.springframework.cache.ehcache.EhCacheManagerFactoryBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.ClassPathResource;@Configuration
@EnableCaching
public class EhcacheConfiguration {@Beanpublic EhCacheManagerFactoryBean cacheManagerFactoryBean(){EhCacheManagerFactoryBean bean = new EhCacheManagerFactoryBean();bean.setConfigLocation(new ClassPathResource("ehcache.xml"));bean.setShared(true);return bean;}@Beanpublic EhCacheCacheManager ehCacheCacheManager(EhCacheManagerFactoryBean bean){return new EhCacheCacheManager(bean.getObject());} 
}

使用

@Service
public class EhcahceServiceImpl implements EhcahceService {private static final String CACHE_STRATEGY = "local";@CachePut(value=CACHE_STRATEGY,key="#root.methodName+#info.getProduct_id()")@Overridepublic ProductInfo saveProductInfo(ProductInfo info) throws Exception {return info;}@Cacheable(value=CACHE_STRATEGY,key="#root.methodName+#id")@Overridepublic ProductInfo getProductInfoById(Long id) throws Exception {return null;}}

使用redis作为缓存

pom坐标

        <!--redis 配置--><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-data-redis</artifactId><exclusions><exclusion><groupId>io.lettuce</groupId><artifactId>lettuce-core</artifactId></exclusion></exclusions></dependency><dependency><groupId>redis.clients</groupId><artifactId>jedis</artifactId></dependency><dependency><groupId>org.apache.commons</groupId><artifactId>commons-pool2</artifactId></dependency>

yml配置

spring:# redis配置redis:password: 123456# 集群模式cluster:nodes: 127.0.0.1:1000,127.0.0.1:2000# 哨兵模式#sentinel:#master: sentinel #哨兵的名字 #下面是所有哨兵集群节点#nodes: 11.11.11.111:26379,11.11.11.111:26380jedis:pool:#最大连接数max-active: 200#最大阻塞等待时间(负数表示没限制)max-wait: -1#最大空闲max-idle: 8#最小空闲min-idle: 0#连接超时时间expireSecond: 604800 #7天

redisCacheManage配置

此处设计了两种不同cacheName的redis缓存

import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.cache.CacheManager;
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.cache.RedisCacheWriter;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.data.redis.serializer.GenericJackson2JsonRedisSerializer;
import org.springframework.data.redis.serializer.RedisSerializationContext;
import org.springframework.data.redis.serializer.StringRedisSerializer;import java.time.Duration;
import java.util.HashMap;
import java.util.Map;@Configuration
@EnableCaching
@Slf4j
public class CacheConfig {@Value("${spring.redis.expireSecond}")private Integer expireSecond;@Beanpublic CacheManager cacheManager(RedisConnectionFactory redisConnectionFactory) {return new RedisCacheManager(RedisCacheWriter.nonLockingRedisCacheWriter(redisConnectionFactory),this.getRedisCacheConfigurationWithTtl(600), // 默认策略，未配置的 key 会使用这个this.getRedisCacheConfigurationMap() // 指定 key 策略);}private Map<String, RedisCacheConfiguration> getRedisCacheConfigurationMap() {Map<String, RedisCacheConfiguration> redisCacheConfigurationMap = new HashMap<>();redisCacheConfigurationMap.put("Dict", this.getRedisCacheConfigurationWithTtl(600));redisCacheConfigurationMap.put("COL_KEY", this.getRedisCacheConfigurationWithTtl(expireSecond));return redisCacheConfigurationMap;}private RedisCacheConfiguration getRedisCacheConfigurationWithTtl(Integer seconds) {RedisCacheConfiguration config = RedisCacheConfiguration.defaultCacheConfig().serializeKeysWith(RedisSerializationContext.SerializationPair.fromSerializer(new StringRedisSerializer())).serializeValuesWith(RedisSerializationContext.SerializationPair.fromSerializer(new GenericJackson2JsonRedisSerializer())).entryTtl(Duration.ofSeconds(seconds));return config;}
}

使用同上

同时使用两种缓存

配置

import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.cache.annotation.EnableCaching;
import org.springframework.cache.ehcache.EhCacheCacheManager;
import org.springframework.cache.ehcache.EhCacheManagerFactoryBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.core.io.ClassPathResource;
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.serializer.GenericJackson2JsonRedisSerializer;
import org.springframework.data.redis.serializer.RedisSerializationContext;
import org.springframework.data.redis.serializer.StringRedisSerializer;import java.time.Duration;@Configuration
@EnableCaching
@Slf4j
public class CacheConfig {@Value("${spring.redis.expireSecond}")private Integer expireSecond;@Beanpublic EhCacheManagerFactoryBean cacheManagerFactoryBean() {EhCacheManagerFactoryBean bean = new EhCacheManagerFactoryBean();bean.setConfigLocation(new ClassPathResource("ehcache.xml"));bean.setShared(true);return bean;}@Bean@Primarypublic EhCacheCacheManager ehCacheCacheManager(EhCacheManagerFactoryBean bean) {return new EhCacheCacheManager(bean.getObject());}@Beanpublic RedisCacheManager redisCacheManager(RedisConnectionFactory redisConnectionFactory) {// 使用缓存的默认配置RedisCacheConfiguration config = RedisCacheConfiguration.defaultCacheConfig().serializeKeysWith(RedisSerializationContext.SerializationPair.fromSerializer(new StringRedisSerializer())).serializeValuesWith(RedisSerializationContext.SerializationPair.fromSerializer(new GenericJackson2JsonRedisSerializer())).entryTtl(Duration.ofSeconds(expireSecond));RedisCacheManager.RedisCacheManagerBuilder builder = RedisCacheManager.builder(redisConnectionFactory).cacheDefaults(config);return builder.build();}
}

指定缓存使用

    @Cacheable(value = CACHE_NAME, key = "#root.methodName+#code",cacheManager = "redisCacheManager")

当redis出现问题时，如何禁用redis，直连数据库

1.yml配置文件忽略掉redis配置 spring.autoconfigure.exclude:org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration
2.根据条件加载CacheConfig类，当spring.redis.useRedis=true时加载，否则不加载@ConditionalOnProperty(prefix = "spring.redis", value = "useRedis", havingValue = "true", matchIfMissing = true)
public class CacheConfig{}

Redis工具类

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONObject;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.data.redis.connection.jedis.JedisConnection;
import org.springframework.data.redis.core.RedisConnectionUtils;
import org.springframework.stereotype.Service;
import redis.clients.jedis.Jedis;import javax.annotation.Resource;@Service
@ConditionalOnProperty(prefix = "spring.redis", value = "useRedis", havingValue = "true", matchIfMissing = true)
public class RedisService {@Resourceprivate RedisConnectionFactory redisConnectionFactory;//会出现循环依赖---Circular reference//RedisService引用JedisPool--JedisPool在RedisService，只有创建RedisService的实例才可以获取JedisPool的bean//所以需要单独拿出JedisPool的bean/*** 获取单个对象** @param prefix* @param key* @param data* @return*/public <T> T get(KeyPrefix prefix, String key, Class<T> data) {JedisConnection jedisConnection = (JedisConnection)RedisConnectionUtils.getConnection(redisConnectionFactory, true);Jedis jedis = null;try {jedis = jedisConnection.getNativeConnection();//生成真正的key  className+":"+prefix;  BasePrefix:id1String realKey = prefix.getPrefix() + key;String sval = jedis.get(realKey);//将String转换为Bean入后传出T t = stringToBean(sval, data);return t;} finally {returnToPool(jedisConnection);}}/*** 移除对象,删除** @param prefix* @param key* @return*/public boolean delete(KeyPrefix prefix, String key) {JedisConnection jedisConnection = (JedisConnection)RedisConnectionUtils.getConnection(redisConnectionFactory, true);Jedis jedis = null;try {jedis = jedisConnection.getNativeConnection();String realKey = prefix.getPrefix() + key;long ret = jedis.del(realKey);return ret > 0;//删除成功，返回大于0} finally {returnToPool(jedisConnection);}}/*** 设置单个、多个对象** @param prefix* @param key* @param value* @return*/public <T> boolean set(KeyPrefix prefix, String key, T value) {JedisConnection jedisConnection = (JedisConnection)RedisConnectionUtils.getConnection(redisConnectionFactory, true);Jedis jedis = null;try {jedis = jedisConnection.getNativeConnection();String realKey = prefix.getPrefix() + key;String s = beanToString(value);if (s == null || s.length() <= 0) {return false;}int seconds = prefix.getExpireSeconds();if (seconds <= 0) { //永不过期jedis.set(realKey, s);} else {jedis.setex(realKey, seconds, s);}return true;} finally {returnToPool(jedisConnection);}}/*** 减少值** @param prefix* @param key* @return*/public <T> Long decr(KeyPrefix prefix, String key) {JedisConnection jedisConnection = (JedisConnection)RedisConnectionUtils.getConnection(redisConnectionFactory, true);Jedis jedis = null;try {jedis = jedisConnection.getNativeConnection();String realKey = prefix.getPrefix() + key;return jedis.decr(realKey);} finally {returnToPool(jedisConnection);}}/*** 增加值** @param prefix* @param key* @return*/public <T> Long incr(KeyPrefix prefix, String key) {JedisConnection jedisConnection = (JedisConnection)RedisConnectionUtils.getConnection(redisConnectionFactory, true);Jedis jedis = null;try {jedis = jedisConnection.getNativeConnection();String realKey = prefix.getPrefix() + key;return jedis.incr(realKey);} finally {returnToPool(jedisConnection);}}/*** 获取key的过期时间*/public <T> Long ttl(KeyPrefix prefix, String key) {JedisConnection jedisConnection = (JedisConnection)RedisConnectionUtils.getConnection(redisConnectionFactory, true);Jedis jedis = null;try {jedis = jedisConnection.getNativeConnection();String realKey = prefix.getPrefix() + key;return jedis.ttl(realKey);} finally {returnToPool(jedisConnection);}}/*** 设置key的过期时间*/public <T> void setExpire(KeyPrefix prefix, String key, int expire) {JedisConnection jedisConnection = (JedisConnection)RedisConnectionUtils.getConnection(redisConnectionFactory, true);Jedis jedis = null;try {jedis = jedisConnection.getNativeConnection();String realKey = prefix.getPrefix() + key;jedis.expire(realKey, expire);} finally {returnToPool(jedisConnection);}}/*** 检查key是否存在** @param prefix* @param key* @return*/public <T> boolean exitsKey(KeyPrefix prefix, String key) {JedisConnection jedisConnection = (JedisConnection)RedisConnectionUtils.getConnection(redisConnectionFactory, true);Jedis jedis = null;try {jedis = jedisConnection.getNativeConnection();String realKey = prefix.getPrefix() + key;return jedis.exists(realKey);} finally {returnToPool(jedisConnection);}}/*** 将字符串转换为Bean对象* <p>* parseInt()返回的是基本类型int 而valueOf()返回的是包装类Integer* Integer是可以使用对象方法的  而int类型就不能和Object类型进行互相转换 。* int a=Integer.parseInt(s);* Integer b=Integer.valueOf(s);*/public static <T> T stringToBean(String s, Class<T> clazz) {if (s == null || s.length() == 0 || clazz == null) {return null;}if (clazz == int.class || clazz == Integer.class) {return ((T)Integer.valueOf(s));} else if (clazz == String.class) {return (T)s;} else if (clazz == long.class || clazz == Long.class) {return (T)Long.valueOf(s);} else {JSONObject json = JSON.parseObject(s);return JSON.toJavaObject(json, clazz);}}/*** 将Bean对象转换为字符串类型** @param <T>*/public static <T> String beanToString(T value) {//如果是nullif (value == null) {return null;}//如果不是nullClass<?> clazz = value.getClass();if (clazz == int.class || clazz == Integer.class) {return "" + value;} else if (clazz == String.class) {return "" + value;} else if (clazz == long.class || clazz == Long.class) {return "" + value;} else {return JSON.toJSONString(value);}}private void returnToPool(JedisConnection jedisConnection) {if (jedisConnection != null) {RedisConnectionUtils.releaseConnection(jedisConnection, redisConnectionFactory);}}public <T> boolean set(String key, T value) {JedisConnection jedisConnection = (JedisConnection)RedisConnectionUtils.getConnection(redisConnectionFactory, true);Jedis jedis = null;try {jedis = jedisConnection.getNativeConnection();//将T类型转换为String类型String s = beanToString(value);if (s == null) {return false;}jedis.set(key, s);return true;} finally {returnToPool(jedisConnection);}}public <T> T get(String key, Class<T> data) {JedisConnection jedisConnection = (JedisConnection)RedisConnectionUtils.getConnection(redisConnectionFactory, true);Jedis jedis = null;try {jedis = jedisConnection.getNativeConnection();String sval = jedis.get(key);//将String转换为Bean入后传出T t = stringToBean(sval, data);return t;} finally {returnToPool(jedisConnection);}}
}