打开项目，找到.settings--->org.eclipse.wst.common.project.facet.core 修改这个文件中：

 

<?xml version="1.0" encoding="UTF-8"?>

<faceted-project>

  <runtime name="Apache Tomcat v7.0"/>

  <fixed facet="java"/>

  <fixed facet="wst.jsdt.web"/>

  <fixed facet="jst.web"/>

  <fixed facet="dorado7.core"/>

  <installed facet="java" version="1.6"/>

  <installed facet="jst.web" version="2.5"/>

  <installed facet="wst.jsdt.web" version="1.0"/>

  <installed facet="dorado7.core" version="1.0"/>

</faceted-project>

将<runtime name="Apache Tomcat v7.0"/>删除掉保存即可