annotation和Spring的动态缓存文章

由于系统需求需要对各个接口进行key-value缓存(以参数为key,返回的对象为value),当然对于这种情况首先考虑到的是使用aop,前段时间看过aspectj的一些介绍,借此机会正好加以应用和体会一下,aspectj是AOP最早成熟的java实现,它稍微扩展了一下java语言,增加了一些keyword等,具体的aspectj的基本语法见[ur=http://today.java.net/pub/a/today/2003/12/26/ch3AspectJSyntaxBasics.html]这里[/url],进行缓存的框架使用较成熟的ehcache.
下面开始进行配置
首先是ehcache的配置文件

<?xml version="1.0" encoding="UTF-8"?>
<ehcache>
    <diskStore path="/home/workspace/gzshine/trunk/ehcache"/>
    <cache name="DEFAULT_CACHE"
        maxElementsInMemory="10000"
        eternal="false"
        timeToIdleSeconds="3600"
        timeToLiveSeconds="3600"
        overflowToDisk="true"
        />
</ehcache>

这个的DEFAULT_CACHE是默认配置,最大的缓存数为10000,时间为一个小时

接下来的是spring下的配置

<?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:aop="http://www.springframework.org/schema/aop"
    xmlns:tx="http://www.springframework.org/schema/tx"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="
       http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
       http://www.springframework.org/schema/tx
       http://www.springframework.org/schema/tx/spring-tx-2.5.xsd
       http://www.springframework.org/schema/aop
       http://www.springframework.org/schema/aop/spring-aop-2.5.xsd
       http://www.springframework.org/schema/context
       http://www.springframework.org/schema/context/spring-context-2.5.xsd">

<!-- ##############  aspectj 4 ehcache   ############# -->

    <aop:aspectj-autoproxy proxy-target-class="true"/>
    <bean id = "methodCacheAspectJ" class="com.***.shine.aspectj.MethodCacheAspectJ" >
        <property name="cache">
            <ref local="methodCache" />
        </property>
    </bean>

    <bean id="cacheManager"
        class="org.springframework.cache.ehcache.EhCacheManagerFactoryBean">
        <property name="configLocation">
            <value>classpath:ehcache.xml</value>
        </property>
    </bean>

    <!-- 定义ehCache的工厂，并设置所使用的Cache name -->

    <bean id="methodCache"
        class="org.springframework.cache.ehcache.EhCacheFactoryBean">
        <property name="cacheManager">
            <ref local="cacheManager" />
        </property>
        <property name="cacheName">
            <value>DEFAULT_CACHE</value>
        </property>
    </bean>

<aop:aspectj-autoproxy proxy-target-class="true"/>
是为aspectj在所有class下开启自动动态代理
<bean id="cacheManager">指定刚刚的ehcache配置文件

接下来编写一个自定义的annotation

package com.***.shine.cache;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target({ElementType.METHOD,ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface MethodCache {
    int second() default 0;
}

<bean id = "methodCacheAspectJ">是一个aspectj进行Pointcuts和Advice的类需注入methodCache

package com.***.shine.aspectj;

@Aspect
public class MethodCacheAspectJ {
    Log logger = LogFactory.getLog(MethodCacheAspectJ.class);

    private Cache cache;

    /**
     * 设置缓存名
     */
    public void setCache(Cache cache) {
        this.cache = cache;
    }

    @Pointcut("@annotation(com.***.shine.cache.MethodCache)")
    public void methodCachePointcut(){
    }

    @Around("methodCachePointcut()")
    public Object methodCacheHold(ProceedingJoinPoint joinPoint) throws Throwable{
        String targetName = joinPoint.getTarget().getClass().getName();
        String methodName = joinPoint.getSignature().getName();
        Object[] arguments = joinPoint.getArgs();
        Object result = null;
        String cacheKey = getCacheKey(targetName, methodName, arguments);
        Element element = cache.get(cacheKey);
        if (element == null) {
            try{
                result = joinPoint.proceed();
            }catch(Exception e){
                logger.info(e);
            }
            if(result!=null){
                try{
                    element = new Element(cacheKey, (Serializable) result);
                    Class targetClass = Class.forName(targetName);
                    Method[] method = targetClass.getMethods();
                    int second = 0;
                    for(Method m:method){
                        if (m.getName().equals(methodName)) {
                            Class[] tmpCs = m.getParameterTypes();
                            if(tmpCs.length==arguments.length){
                                MethodCache methodCache = m.getAnnotation(MethodCache.class);
                                second = methodCache.second();
                                break;
                            }
                        }
                    }
                    if(second>0){ // annotation没有设second值则使用ehcache.xml中自定义值
                        element.setTimeToIdle(second);
                        element.setTimeToLive(second);
                    }
                    cache.put(element);
                }catch(Exception e){
                    logger.info("!!!!!!!!!"+cacheKey+"!!!!!!!!!未能执行方法缓存"+e);
                }
            }
        }
        return element.getValue();
    }

     private String getCacheKey(String targetName, String methodName,
            Object[] arguments) {
        StringBuffer sb = new StringBuffer();
        sb.append(targetName).append(".").append(methodName);
        if ((arguments != null) && (arguments.length != 0)) {
            for (int i = 0; i < arguments.length; i++) {
                if (arguments[i] instanceof Date) {
                    sb.append(".").append(
                            DateUtil.datetoString((Date) arguments[i]));
                } else {
                    sb.append(".").append(arguments[i]);
                }
            }
        }
        return sb.toString();
    }
}

@Pointcut("@annotation(com.netease.shine.cache.MethodCache)")
对有应用com.netease.shine.cache.MethodCache进行注解的方法进行横切面拦截
@Around("methodCachePointcut()")
并在Advice中处理这个Pointcut,这里的的Advice使用的是Around(环绕通知)
String cacheKey = getCacheKey(targetName, methodName, arguments);
接下来使用类型,方法名,参数为key进入缓存处理
Element element = cache.get(cacheKey);
当然如果在cache队列中取得非null对象则直接返回该对象
MethodCache methodCache = m.getAnnotation(MethodCache.class);
second = methodCache.second();
取得second的值(缓存的时间,如在@annotation中无重写只为int second() default 0)
element.setTimeToIdle(second);
element.setTimeToLive(second);
如果非零则重新设置缓存时间

@MethodCache(second=300)
public List<Sort> getSort(int type,int parentid){
    System.out.println("!!!!!!!!!!!!!没缓存到");
    Row row = new Row();
    row.put("type", type);
    row.put("parentid", parentid);
    return (List<Sort>)gz_Template.queryForList("sort.getSort", row);
}

最后需要将@MethodCache要缓存方法的实现类