缓存插件 Spring支持EHCache缓存

　　Spring仅仅是提供了对缓存的支持，但它并没有任何的缓存功能的实现，spring使用的是第三方的缓存框架来实现缓存的功能。其中，spring对EHCache提供了很好的支持。

 

在介绍Spring的缓存配置之前，我们先看一下EHCache是如何配置。 

<?xml version="1.0" encoding="UTF-8" ?> <ehcache><!-- 定义默认的缓存区，如果在未指定缓存区时，默认使用该缓存区 --><defaultCache maxElementsInMemory="500" eternal="true"overflowToDisk="false" memoryStoreEvictionPolicy="LFU"></defaultCache><!-- 定义名字为"dao.select"的缓存区 --><cache name="dao.select" maxElementsInMemory="500" eternal="true"overflowToDisk="false" memoryStoreEvictionPolicy="LFU" /> </ehcache>

 

 由于Spring的缓存机制是基于Spring的AOP，那么在Spring Cache中应该存在着一个Advice。没错，在Spring Cache中的Advice是存在的，它就是org.springframework.cache.Cache。我们看一下它的接口定义： 

/** Copyright 2002-2011 the original author or authors.** Licensed under the Apache License, Version 2.0 (the "License");* you may not use this file except in compliance with the License.* You may obtain a copy of the License at** http://www.apache.org/licenses/LICENSE-2.0** Unless required by applicable law or agreed to in writing, software* distributed under the License is distributed on an "AS IS" BASIS,* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.* See the License for the specific language governing permissions and* limitations under the License.*/package org.springframework.cache;/*** Interface that defines the common cache operations.** <b>Note:</b> Due to the generic use of caching, it is recommended that* implementations allow storage of <tt>null</tt> values (for example to* cache methods that return {@code null}).** @since 3.1*/ public interface Cache {/*** Return the cache name.*/String getName();/*** Return the the underlying native cache provider.*/Object getNativeCache();/*** Return the value to which this cache maps the specified key. Returns* <code>null</code> if the cache contains no mapping for this key.* @param key key whose associated value is to be returned.* @return the value to which this cache maps the specified key,* or <code>null</code> if the cache contains no mapping for this key*/ValueWrapper get(Object key);/*** Associate the specified value with the specified key in this cache.* <p>If the cache previously contained a mapping for this key, the old* value is replaced by the specified value.* @param key the key with which the specified value is to be associated* @param value the value to be associated with the specified key*/void put(Object key, Object value);/*** Evict the mapping for this key from this cache if it is present.* @param key the key whose mapping is to be removed from the cache*/void evict(Object key);/*** Remove all mappings from the cache.*/void clear();/*** A (wrapper) object representing a cache value.*/interface ValueWrapper {/*** Return the actual value in the cache.*/Object get();}}

 

 evict,put方法就是Advice的功能方法，或者可以这样去理解。

 但spring并不是直接使用org.springframework.cache.Cache，spring把Cache对象交给org.springframework.cache.CacheManager来管理，下面是org.springframework.cache.CacheManager接口的定义：

/** Copyright 2002-2011 the original author or authors.** Licensed under the Apache License, Version 2.0 (the "License");* you may not use this file except in compliance with the License.* You may obtain a copy of the License at** http://www.apache.org/licenses/LICENSE-2.0** Unless required by applicable law or agreed to in writing, software* distributed under the License is distributed on an "AS IS" BASIS,* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.* See the License for the specific language governing permissions and* limitations under the License.*/package org.springframework.cache;import java.util.Collection;/*** A manager for a set of {@link Cache}s.** @since 3.1*/ public interface CacheManager {/*** Return the cache associated with the given name.* @param name cache identifier (must not be {@code null})* @return associated cache, or {@code null} if none is found*/Cache getCache(String name);/*** Return a collection of the caches known by this cache manager.* @return names of caches known by the cache manager.*/Collection<String> getCacheNames();}

 

 在spring对EHCache的支持中，org.springframework.cache.ehcache.EhCacheManager就是org.springframework.cache.CacheManager的一个实现

　<!-- 该Bean是一个org.springframework.cache.CacheManager对象属性cacheManager是一个net.sf.ehcache.CacheManager对象--><bean id="cacheManager" class="org.springframework.cache.ehcache.EhCacheCacheManager"><property name="cacheManager"><bean class="org.springframework.cache.ehcache.EhCacheManagerFactoryBean"><property name="configLocation" value="classpath:ehcache-config.xml"></property></bean></property></bean>

 

 基于xml方式的缓存配置

<beans xmlns="http://www.springframework.org/schema/beans"xmlns:cache="http://www.springframework.org/schema/cache"xmlns:context="http://www.springframework.org/schema/context"xmlns:aop="http://www.springframework.org/schema/aop" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans-3.1.xsdhttp://www.springframework.org/schema/contexthttp://www.springframework.org/schema/context/spring-context-3.1.xsdhttp://www.springframework.org/schema/cachehttp://www.springframework.org/schema/cache/spring-cache-3.1.xsdhttp://www.springframework.org/schema/aophttp://www.springframework.org/schema/aop/spring-aop-3.1.xsd"><context:component-scan base-package="com.sin90lzc"></context:component-scan><bean id="cacheManager" class="org.springframework.cache.ehcache.EhCacheCacheManager"><property name="cacheManager"><bean class="org.springframework.cache.ehcache.EhCacheManagerFactoryBean"><property name="configLocation" value="classpath:ehcache-config.xml"></property></bean></property></bean><cache:advice id="cacheAdvice" cache-manager="cacheManager"><cache:caching><cache:cacheable cache="dao.select" method="select"key="#id" /><cache:cache-evict cache="dao.select" method="save"key="#obj" /></cache:caching></cache:advice><aop:config><aop:advisor advice-ref="cacheAdvice" pointcut="execution(* com.sin90lzc.train.spring_cache.simulation.DaoImpl.*(..))"/></aop:config> </beans>

 

 

 注解驱动缓存配置

<beans xmlns="http://www.springframework.org/schema/beans"xmlns:cache="http://www.springframework.org/schema/cache"xmlns:context="http://www.springframework.org/schema/context"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans-3.1.xsdhttp://www.springframework.org/schema/contexthttp://www.springframework.org/schema/context/spring-context-3.1.xsdhttp://www.springframework.org/schema/cachehttp://www.springframework.org/schema/cache/spring-cache-3.1.xsd"><context:component-scan base-package="com.sin90lzc"></context:component-scan><!-- 该Bean是一个org.springframework.cache.CacheManager对象属性cacheManager是一个net.sf.ehcache.CacheManager对象--><bean id="cacheManager" class="org.springframework.cache.ehcache.EhCacheCacheManager"><property name="cacheManager"><bean class="org.springframework.cache.ehcache.EhCacheManagerFactoryBean"><property name="configLocation" value="classpath:ehcache-config.xml"></property></bean></property></bean><cache:annotation-driven /><!-- 启用缓存注解功能，这个是必须的，否则注解不会生效，另外，该注解一定要声明在spring主配置文件中才会生效 --><!-- <cache:annotation-driven cache-manager="cacheManager"/> --></beans>

 

 

 

 

 

package com.sin90lzc.train.spring_cache.simulation;import org.springframework.cache.annotation.CacheEvict; import org.springframework.cache.annotation.Cacheable; import org.springframework.stereotype.Component;@Component public class DaoImpl implements Dao {/*** value定义了缓存区（缓存区的名字），每个缓存区可以看作是一个Map对象* key作为该方法结果缓存的唯一标识，*/@Cacheable(value = { "dao.select" },key="#id")@Overridepublic Object select(int id) {System.out.println("do in function select()");return new Object();}@CacheEvict(value = { "dao.select" }, key="#obj")@Overridepublic void save(Object obj) {System.out.println("do in function save(obj)");}}

 

@Cacheable：负责将方法的返回值加入到缓存中
@CacheEvict：负责清除缓存

 @Cacheable 支持如下几个参数：
value：缓存位置名称，不能为空，如果使用EHCache，就是ehcache.xml中声明的cache的name
key：缓存的key，默认为空，既表示使用方法的参数类型及参数值作为key，支持SpEL
condition：触发条件，只有满足条件的情况才会加入缓存，默认为空，既表示全部都加入缓存，支持SpEL

 例如：

//将缓存保存进andCache，并使用参数中的userId加上一个字符串(这里使用方法名称)作为缓存的key @Cacheable(value="andCache",key="#userId + 'findById'") public SystemUser findById(String userId) {SystemUser user = (SystemUser) dao.findById(SystemUser.class, userId);return user ; } //将缓存保存进andCache，并当参数userId的长度小于32时才保存进缓存，默认使用参数值及类型作为缓存的key @Cacheable(value="andCache",condition="#userId.length < 32") public boolean isReserved(String userId) {System.out.println("hello andCache"+userId);return false; }

 

 @CacheEvict 支持如下几个参数：
value：缓存位置名称，不能为空，同上
key：缓存的key，默认为空，同上
condition：触发条件，只有满足条件的情况才会清除缓存，默认为空，支持SpEL
allEntries：true表示清除value中的全部缓存，默认为false
 
例如：

//清除掉指定key的缓存 @CacheEvict(value="andCache",key="#user.userId + 'findById'") public void modifyUserRole(SystemUser user) {System.out.println("hello andCache delete"+user.getUserId()); } &nbsp;//清除掉全部缓存 @CacheEvict(value="andCache",allEntries=true) public final void setReservedUsers(String[] reservedUsers) {System.out.println("hello andCache deleteall"); }

 

转载于:https://www.cnblogs.com/hwaggLee/p/4443155.html

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