我的servlet的.java文件ServletToJsp.java源码如下:

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class ServletToJsp extends HttpServlet
{
   public void doGet(HttpServletRequest req,HttpServletResponse res)throws ServletException,IOException
   {
      try{
          req.setAttribute("ServletName","ServletToJsp");
          getServletConfig().getServletContext().getRequestDipatcher("/ServletUseJsp.jsp").forward(req.res);
}
catch(Exception e){
e.printStackTrace();}

用javac编译时出现如下错误:
ServletToJsp.java:2: 软件包 javax.servlet 不存在
import javax.servlet.*;
^
ServletToJsp.java:3: 软件包 javax.servlet.http 不存在
import javax.servlet.http.*;
^
ServletToJsp.java:4: 找不到符号
符号： 类 HttpServlet
public class ServletToJsp extends HttpServlet
                                  ^
ServletToJsp.java:6: 找不到符号
符号： 类 HttpServletRequest
位置： 类 ServletToJsp
   public void doGet(HttpServletRequest req,HttpServletResponse res)throws ServletException,IOException
                     ^
ServletToJsp.java:6: 找不到符号
符号： 类 HttpServletResponse
位置： 类 ServletToJsp
   public void doGet(HttpServletRequest req,HttpServletResponse res)throws ServletException,IOException
                                            ^
ServletToJsp.java:6: 找不到符号
符号： 类 ServletException
位置： 类 ServletToJsp
   public void doGet(HttpServletRequest req,HttpServletResponse res)throws ServletException,IOException
                                                                           ^
ServletToJsp.java:10: 找不到符号
符号： 方法 getServletConfig()
位置： 类 ServletToJsp
          getServletConfig().getServletContext().getRequestDipatcher("/ServletUseJsp.jsp").forward(req.res);

请大家帮忙解决.
          ^