eclipse中修改web Module
在eclipse的工程上选择属性，再选择Project Facets里面中选择Dynamic Web Module ，将3.0修改为2.5，提示如下信息：
Cannot change version of project facet Dynamic Web Module to 2.5
修改办法：
Open the navigator view and find that there is a .settings folder under your project expand it and then open the file: org.eclipse.wst.common.project.facet.core.