guava cache与spring集成

时间 2019-11-12

原文原文链接

缓存的背景

缓存，在咱们平常开发中是必不可少的一种解决性能问题的方法。简单的说，cache 就是为了提高系统性能而开辟的一块内存空间。在cpu进行计算的时候，首先是读取寄存器，而后内存，再是硬盘。因为寄存器容量很小，不太适合存储咱们须要快速读取的数据，放在硬盘中话，效率过低，因此大多数人将一些静态资源或者不常常修改的数据放在内存中。　java

缓存的做用

缓存的主要做用是暂时在内存中保存业务系统的数据处理结果，而且等待下次访问使用。在平常开发的不少场合，因为受限于硬盘 IO的性能或者咱们自身业务系统的数据处理和获取可能很是费时，当咱们发现咱们的系统这个数据请求量很大的时候，频繁的IO和频繁的逻辑处理会致使硬盘和CPU资源的瓶颈出现。缓存的做用就是将这些来自不易的数据保存在内存中，当有其余线程或者客户端须要查询相同的数据资源时，直接从缓存的内存块中返回数据，这样不但能够提升系统的响应时间，同时也能够节省对这些数据的处理流程的资源消耗，总体上来讲，系统性能会有大大的提高。redis

guava cache与spring整合

你们都清楚，相对于静态Map实现本地缓存而言guava cache提供了许多种对缓存管理策略，好比：缓存个数、缓存生存期、缓存提取策略（LRU）等, 也正是这样，guava cache在本地缓存层面上使用是开发人员的首选。而在企业开发中spring是用的最多的，若是将guava cache与spring整合，依靠spring强大的IOC和AOP在使用缓存时是很方便、快捷的，而要实现spring与guava cache整合只须要如下三个步骤就能够搞定：spring

创建spring-cache.xml

首先创建spring-cache.xml 里面配置spring对guava cache基本参数的管理，以下：缓存

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:c="http://www.springframework.org/schema/c"
       xmlns:p="http://www.springframework.org/schema/p"
       xmlns:cache="http://www.springframework.org/schema/cache"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd
		http://www.springframework.org/schema/cache http://www.springframework.org/schema/cache/spring-cache-4.0.xsd">

    <!--启动注解  进行guava cache 管理-->
    <cache:annotation-driven cache-manager="cacheManager" proxy-target-class="true"/>
    <bean id="cacheManager" class="org.springframework.cache.support.CompositeCacheManager">
        <property name="cacheManagers">
            <list>
	    <!--将guava cache交于spring管理  若是要实现redis  也能够加在这里-->
                <ref bean="guavaCacheManager"/>
            </list>
        </property>
        <property name="fallbackToNoOpCache" value="true"/>
    </bean>

 <!--配置guava cache须要缓存的key  以及创建方式-->
    <bean id="guavaCacheManager" class="com.daojia.open.confluence.worker.common.GuavaCacheManager">
        <property name="configMap">
            <map key-type="java.lang.String" value-type="com.google.common.cache.CacheBuilder">
                <entry key="indexReptileKeyValue" value-ref="defaultCacheBuilder"/>
            </map>
        </property>
    </bean>
<!--设置guava cache缓存策略  生存期为24小时  最大100个缓存数-->
    <bean id="defaultCacheBuilder"
          class="com.google.common.cache.CacheBuilder"
          factory-method="from">
        <constructor-arg value="maximumSize=100, expireAfterWrite=24h"/>
    </bean>
</beans>

实现spring对外提供的接口

上面配置了将guavaCacheManager交于spring管理，那么久要实现这个管理类，该类若是要被spring容器管理的话须要实现AbstractTransactionSupportingCacheManager接口，该接口支持事物回滚，当缓存失败，会将错误数据还原。具体实现以下：app

package com.daojia.open.confluence.worker.common;

import com.google.common.cache.CacheBuilder;
import com.google.common.collect.Maps;
import org.springframework.cache.Cache;
import org.springframework.cache.transaction.AbstractTransactionSupportingCacheManager;

import java.util.Collection;
import java.util.Map;
import java.util.concurrent.ConcurrentMap;

/**
 * guavacache支持事务回滚，重写manager。
 * cache的构建使用builder配置构建
 */
public class GuavaCacheManager  extends AbstractTransactionSupportingCacheManager {

    private final ConcurrentMap<String, Cache> cacheMap = Maps.newConcurrentMap();

    private boolean dynamic = true;

    private Map<String, CacheBuilder> builderMap = Maps.newHashMap();

    private boolean allowNullValues = true;

    @Override
    protected Collection<? extends Cache> loadCaches() {
        Collection<Cache> values = cacheMap.values();
        return values;
    }

    @Override
    public Cache getCache(String name) {
        Cache cache = this.cacheMap.get(name);
        if (cache == null && this.dynamic) {
            synchronized (this.cacheMap) {
                cache = this.cacheMap.get(name);
                if (cache == null && this.builderMap.containsKey(name)) {
                    CacheBuilder builder = this.builderMap.get(name);
                    cache = createGuavaCache(name, builder);
                    this.cacheMap.put(name, cache);
                }
            }
        }
        return cache;
    }

    protected Cache createGuavaCache(String name, CacheBuilder builder) {
        com.google.common.cache.Cache<Object, Object> cache = null;
        if(builder == null){
            cache = CacheBuilder.newBuilder().build();
        }else{
            cache = builder.build();
        }
        return new GuavaCache(name, cache, isAllowNullValues());
    }


    public boolean isAllowNullValues() {
        return this.allowNullValues;
    }

    public void setConfigMap(Map<String, CacheBuilder> configMap) {
        this.builderMap = configMap;
    }

}

这仅仅是对guava cache管理还须要一个具体的缓存操做类，该类也是同样要被spring管理，要实现一个cache接口，该接口是spring对外缓存管理的统一接口，只要实现该接口的缓存，都能被spring管理起来，好比guava cache 以下：ide

package com.daojia.open.confluence.worker.common;

import com.daojia.open.confluence.worker.utils.JsonMapper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.cache.Cache;
import org.springframework.cache.support.SimpleValueWrapper;
import org.springframework.util.Assert;

import java.io.Serializable;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;

public class GuavaCache implements Cache {

    private static Logger log = LoggerFactory.getLogger(GuavaCache.class);

    private final JsonMapper mapper = new JsonMapper();

    private static final Object NULL_HOLDER = new NullHolder();

    private final String name;

    private final com.google.common.cache.Cache<Object, Object> cache;

    private final boolean allowNullValues;

    public GuavaCache(String name, com.google.common.cache.Cache<Object, Object> cache) {
        this(name, cache, true);
    }

    public GuavaCache(String name, com.google.common.cache.Cache<Object, Object> cache, boolean allowNullValues) {
        Assert.notNull(name, "Name must not be null");
        Assert.notNull(cache, "Cache must not be null");
        this.name = name;
        this.cache = cache;
        this.allowNullValues = allowNullValues;
    }



    @Override
    public String getName() {
        return this.name;
    }

    @Override
    public Object getNativeCache() {
        return this.cache;
    }

    @Override
    public ValueWrapper get(Object key) {
        key = getKey(key.toString());
        Object value = this.cache.getIfPresent(key);
        log.info("获取缓存key={},获取对象={}", key, mapper.toJson(value));
        return toWrapper(value);
    }

    @Override
    public <T> T get(Object key, Class<T> type) {
        key = getKey(key.toString());
        Object value = fromStoreValue(this.cache.getIfPresent(key));
        log.info("获取缓存key={},获取对象={}", key, mapper.toJson(value));
        if (value != null && type != null && !type.isInstance(value)) {
            throw new IllegalStateException("Cached value is not of required type [" + type.getName() + "]: " + value);
        }
        return (T) value;
    }

    @Override
    public void put(Object key, Object value) {
        key = getKey(key.toString());
        this.cache.put(key, toStoreValue(value));
        log.info("存入缓存key=={},存入对象={}", key, mapper.toJson(value));
    }

    @Override
    public ValueWrapper putIfAbsent(Object key, Object value) {
        try {
            PutIfAbsentCallable callable = new PutIfAbsentCallable(value);
            Object result = this.cache.get(key, callable);
            return (callable.called ? null : toWrapper(result));
        }
        catch (ExecutionException ex) {
            throw new IllegalStateException(ex);
        }
    }

    @Override
    public void evict(Object key) {
        this.cache.invalidate(key);
        log.info("删除缓存key={}",key);
    }

    @Override
    public void clear() {
        this.cache.invalidateAll();
        log.info("清空guavacache全部缓存");
    }

    private ValueWrapper toWrapper(Object value) {
        return (value != null ? new SimpleValueWrapper(fromStoreValue(value)) : null);
    }


    protected Object fromStoreValue(Object storeValue) {
        if (this.allowNullValues && storeValue == NULL_HOLDER) {
            return null;
        }
        return storeValue;
    }

    public final boolean isAllowNullValues() {
        return this.allowNullValues;
    }

    @SuppressWarnings("serial")
    private static class NullHolder implements Serializable {
    }

    protected Object toStoreValue(Object userValue) {
        if (this.allowNullValues && userValue == null) {
            return NULL_HOLDER;
        }
        return userValue;
    }

    private class PutIfAbsentCallable implements Callable<Object> {

        private final Object value;

        private boolean called;

        public PutIfAbsentCallable(Object value) {
            this.value = value;
        }

        @Override
        public Object call() throws Exception {
            this.called = true;
            return toStoreValue(this.value);
        }
    }

    /**实现key增长cache名称**/
    private String getKey(String key) {
        return name + "_" + key;
    }
}

编写sqel语法对缓存进行管理

当完成这上面两个步骤以后，代表你的guava cache已被spring管理起来了，这时能够熟悉一下sqel注释语法，这是spring 对缓存进行注解管理用到经常使用语法，好比获取缓存：性能

/*当使用到该方法的时候  spring会首先判断缓存中是否含有该key的值 ，若是有则从本地缓存中获取
  并以你输入的参数indexReptileKey为key获取，不然从执行方法体中的获取  并将获取的数据放入到缓存中*/
    @Cacheable(value = "indexReptileKeyValue", key = "#indexReptileKey")
    public List<IndexReptilePJO> getReptile(int indexReptileKey) throws Exception {
        LOGGER.info("不走guava cache获取参数");
        return super.handlerindexReptile();
    }

放入缓存以下:ui

/*设置某个值的时候，想将该值存入缓存  则用这个注解  将你须要设置的值设置到缓存中 
  另外一个方法在获取的时候就是从缓存中获取*/
   @CachePut(value = "indexReptileKeyValue", key = "#indexReptileKey")
    public List<IndexReptilePJO> setReptile(int indexReptileKey) throws Exception {
        LOGGER.info("将树节点项目路径  存入guava cache中");
        return super.handlerindexReptile();
    }