Spring4+Ehcache缓存无效

[finemi]

<!-- 缓存配置 -->  
    <cache:annotation-driven cache-manager="cacheManager"/>  
    <bean id="cacheManagerFactory" class="org.springframework.cache.ehcache.EhCacheManagerFactoryBean">  
        <property name="configLocation" value="classpath:ehcache.xml"/>  
    </bean>  
    <bean id="cacheManager" class="org.springframework.cache.ehcache.EhCacheCacheManager">  
        <property name="cacheManager" ref="cacheManagerFactory"/>  
    </bean> 

<!-- Ehcache配置 -->  
<ehcache>
    <diskStore path="java.io.tmpdir"/>
    <defaultCache
        maxElementsInMemory="10000"
        eternal="true"
        timeToIdleSeconds="0"
        timeToLiveSeconds="0"
        overflowToDisk="true"
        diskPersistent="false"
        />
</ehcache>

@Cacheable(value="myCache",key="#num")
	public int cache(int num){
		System.out.println("执行....");
		return new Random().nextInt(10); 
	}

       public void test(){
		System.out.println(cache(3));
                System.out.println(cache(3));
	}

每次都会真实执行cache方法！不知道到底错在哪里。@Cacheable的value是随便填的吗？