package myservlet.control;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.ServletConfig;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class method2 extends HttpServlet {    @Override    public void init(ServletConfig config) throws ServletException {        // TODO Auto-generated method stub        super.init(config);    }    @Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp)            throws ServletException, IOException {        // TODO Auto-generated method stub        //super.doPost(req, resp);        req.setCharacterEncoding("gb2312");        resp.setContentType("text/html;charset=gb2312");        PrintWriter out = resp.getWriter();        String name = req.getParameter("name");        String num[] = name.split("[,,]");        String method = req.getMethod();        double sum = 0;        for (String item:num) {            if(item.length()>=1)            sum += Double.parseDouble(item);        }        out.print("用户的请求方式为" + method );        for (String item:num) {            if(item.length()>=1)            out.print(item+"");        }        out.print("和是"+sum);    }    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp)            throws ServletException, IOException {        // TODO Auto-generated method stub      // super.doGet(req, resp);        req.setCharacterEncoding("gb2312");        resp.setContentType("text/html;charset=gb2312");        PrintWriter out = resp.getWriter();        String name = req.getParameter("name");        String num[] = name.split("[,,]");        String method = req.getMethod();        double product = 1;        for (String item:num) {            if(item.length()>=1)                product *= Double.parseDouble(item);        }        out.print("用户的请求方式为" + method );        for (String item:num) {            if(item.length()>=1)            out.print(item+"");        }        out.print("积是"+product);    }    }

是因为重写doPost或doGet方法时

super.doPost(req, resp);

super.doGet(req, resp); 去掉这2句话就可以了

 

HTTP Status 500 -

org.apache.jasper.JasperException: /Login/login.jsp(27,12) According to TLD, tag jsp:getProperty must be empty, but is not 错误的原因是:
    最后这里少了反斜杠