求助,Mybatis3在Spring中的mapper(xml文件)中不能读取properties属性

[felix.shao]

一、属性文件、conf.properties
flushInterval=20000

二、mybatis配置文件：mybatis-config.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration PUBLIC "-//www.mybatis.org//DTD Config 3.0//EN"
"http://www.mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<properties resource="classpath:conf.properties"/>
<settings>
<setting name="logImpl" value="LOG4J" />
</settings>
</configuration>

三、mybatis的mapper文件
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="com.octlink.tec2.bus.system.news.dao.AdvertisementDao">
<cache flushInterval="${flushInterval}" readOnly="true"></cache>

请问怎么才能使用读取到 conf.propertie的flushInterval=20000属性，谢谢！

[jrhing]

用cache-ref