The type javax.servlet.http.HttpServletRequest cannot be resolved.

链接地址：http://blog.csdn.net/smartzhaomin/article/details/19487907

he type javax.servlet.http.HttpServletRequest cannot be resolved. It is indirectly referenced from 
 required .class files

是缺少serverlet的引用库，解决如下
1.工程右键-properties->java build path
2.在java build path的libraries tab页中选择Add external Jars...按钮
3. 选择eclipse的安装目录，我的是绿色版本，我本机的路径如下，你自己需要根据自己的路径查找添加。E:\eclipse-java-indigo-SR1-win32\eclipse\plugins 选择javax.servlet.jsp_2.0.0.v201101211617.jar；javax.servlet_2.5.0.v201103041518.jar 进行添加即可
注释：由于版本不同，文件包名可能稍有区别。