Can not find the tag library descriptor for "http://java.sun.com/jsp/ jstl/core"

1，Can not find the tag library descriptor for "http://java.sun.com/jsp/ jstl/core" - Can not find the tag library descriptor for "http://java.sun.com/jsp/ jstl/core"

这个错误需导入java包

2，

现象：项目导进eclipse，在其中运行tomcat，会报如下错：
“ Could not load the Tomcat server configuration at \Servers\Tomcat v6.0 Server @ localhost-config. The configuration may be corrupt or incomplete.

Resource is out of sync with the file system: /Servers/Tomcat v6.0 Server @ localhost-config/server.xml.”

解决方法是：
Window -> Preferences -> General -> Workspace，钩选上“Refresh automatically”。
或者自己手动刷新一下。
eclipse document上说： External changes to resources will not be reflected in the workspace and resource objects until detected by the resources plug-in. （因为外部的文件系统的改变不能和工作台同步）