jsp问题

程序没问题 为什么跳出来的是三个 null
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import javax.servlet.*;
import javax.servlet.http.*;

import *;

public class ThreeParams extends HttpServlet{

    private static final long serialVersionUID = 1L;

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=GBK");
        //解决post方式提交内容的乱码
        //一定要写在存取第一个参数之前
        request.setCharacterEncoding("GBK");
        
        //解决get方式乱码问题：-->URIEncoding="GBK"
        
        PrintWriter out = response.getWriter();
        out.println(request.getParameter("param1"));
        out.println("<br>");
        out.println(request.getParameter("param2"));
        out.println("<br>");
        out.println(request.getParameter("param3"));
        out.println("<br>");
        System.out.println("in doGet");
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
        System.out.println("in doPost");
        doGet(request, response);
    }
}