java.lang.NoClassDefFoundError: org/apache/commons/collections/map/LRUMap

Error creating bean with name 'springsessionFactory' defined in ServletContext resource [/WEB-INF/applicationContext.xml]: Invocation of init method failed; nested exception is java.lang.NoClassDefFoundError: org/apache/commons/collections/map/LRUMap

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1332)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:476)

在进行ssh框架整合时遇到的错误，整整弄了两。总是报找不到"NoClassDefFoundError: org/apache/commons/collections/map/LRUMap".我在commons-collections-2.1.1.jar包中找到了LRUMap.class文件但他没在map文件夹下而是直接放在了collections下。后来换了个包commons-collections-3.1.jar，不报错了。才明白原来是包导的不对啊。