问题描述

用户名和密码与后台的数据库无法验证后无法跳转错误页面（用Servlet写的）

这是check.java
package servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.ResultSet;
import java.sql.SQLException;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import bean.sqlBean;

public class check extends HttpServlet {

/**
 * Constructor of the object.
 */
public check() {
    super();
}

/**
 * Destruction of the servlet. <br>
 */
public void destroy() {
    super.destroy(); // Just puts "destroy" string in log
    // Put your code here
}

/**
 * The doGet method of the servlet. <br>
 *
 * This method is called when a form has its tag value method equals to get.
 *
 * @param request the request send by the client to the server
 * @param response the response send by the server to the client
 * @throws ServletException if an error occurred
 * @throws IOException if an error occurred
 */
public void doGet(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {

    response.setContentType("text/html;charset=utf-8");
    PrintWriter out = response.getWriter();
    String id=null;
    String password=null;
    String kind=null;
    id=request.getParameter("id");
    HttpSession session=request.getSession(true);
    session.setAttribute("id", String.valueOf(id));
    password=request.getParameter("password");
    kind=request.getParameter("kind");

    sqlBean db=new sqlBean();
    String pw="";
    String sql="select password from "+kind+" where id='"+id+"'";
    ResultSet rs=db.executeQuery(sql);
    try{
        if(rs.next()){
            pw=rs.getString("password");
            if(password.equals(pw))
                goo(request,response,kind);
            else{
                System.err.println("?????????????");
                doError(request,response,"?????????????");
            }
        }
    }
    catch(SQLException e){
        System.err.println("?????????????"+e.getMessage());
        System.out.print("?????????????"+e.getMessage());
    }
    catch(ServletException f){
        System.err.println("?????????????"+f.getMessage());
    }
    catch(IOException g){
        System.err.println("?????????????"+g.getMessage());
    }
}

/**
 * The doPost method of the servlet. <br>
 *
 * This method is called when a form has its tag value method equals to post.
 *
 * @param request the request send by the client to the server
 * @param response the response send by the server to the client
 * @throws ServletException if an error occurred
 * @throws IOException if an error occurred
 */
public void goo(HttpServletRequest request,HttpServletResponse response,String kind)
throws ServletException,IOException{
    if(kind.equals("student")){
        //??????????
        RequestDispatcher rd=getServletContext().getRequestDispatcher("/student/student.jsp");
        rd.forward(request, response);
    }
    if(kind.equals("teacher")){
        RequestDispatcher rd=getServletContext().getRequestDispatcher("/teacher/teacher.jsp");
        rd.forward(request, response);
    }
    if(kind.equals("manager")){
        RequestDispatcher rd=getServletContext().getRequestDispatcher("/manager/manager.jsp");
        rd.forward(request, response);
    }
}
public void doError(HttpServletRequest request,HttpServletResponse response,String str)
        throws ServletException,IOException{
            request.setAttribute("problem", str);
            getServletConfig().getServletContext().getRequestDispatcher("/errorpage.jsp");
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    doGet(request,response);
}

/**
 * Initialization of the servlet. <br>
 *
 * @throws ServletException if an error occurs
 */
public void init() throws ServletException {
    // Put your code here
}

}

这是errorpage.jsp
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<%=request.getAttribute("problem") %>

请问是什么问题，是check.java里面哪里写的不对吗？

解决方案

你改成这样写 试试
RequestDispatcher rd=getServletContext().getRequestDispatcher("/errorpage.jsp");
rd.forward(request, response);

用debug跟踪一下

解决方案二：

走到这里了吗？

request.setAttribute("problem", str);
getServletConfig().getServletContext().getRequestDispatcher("/errorpage.jsp");