在problems中显示错误是：Target runtime Apache Tomcat 6.0 is not defined。解决方法是：在工程目录下的.settings文件夹里，打开 org.eclipse.wst.common.project.facet.core.xml文件，其内容是：
<?xmlversionxmlversion="1.0"encoding="UTF-8"?>
<faceted-project>
<runtimenameruntimename="Apache Tomcat v6.0"/>
<fixedfacetfixedfacet="jst.web"/>
<fixedfacetfixedfacet="jst.java"/>
<installedfacetinstalledfacet="jst.java"version="6.0"/>
<installedfacetinstalledfacet="jst.web"version="2.5"/>
<installedfacetinstalledfacet="wst.jsdt.web"version="1.0"/>
</faceted-project>
将其修改为：
<?xml version="1.0" encoding="UTF-8" ?>
<faceted-project>
</faceted-project>
