解决 String cannot be resolved to a type

报错内容: 

Multiple annotations found at this line: 
- String cannot be resolved to a type 
- The method getContextPath() from the type HttpServletRequest refers to the missing type String

解决办法: 
首先 右击该项目 - Build Path - Configure Build Path ， 在 Libraries 选项下，会发现有个出错的jre Libraries，将其Remove掉。 
然后 右击该项目 - Build Path - Add Library， 选择JRE System Library，选择Workspace defaulr JRE(jdk1.6)(此前JDK已成功安装并配置好)， 然后 Finish 。