login_confirm.java

这是书上的<java毕业设计指南与项目实践>的第6章:基于JSP+JavaBean+Servlet的课程管理系统,供大家参考

package com.course;
import java.io.*;
import java.sql.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class login_confirm extends HttpServlet{

 //响应Post请求
 public void doPost(HttpServletRequest req, HttpServletResponse res)
    throws ServletException, IOException {	
        
   String message=null; 
   String id=null;
   //接收用户的登录名
   id=req.getParameter("id");
   //创建session对象
   HttpSession session=req.getSession(true);
   //将用户登录名存入session中
   session.setAttribute("id",String.valueOf(id));
   String password=null;
   //接收用户登录的密码
   password= req.getParameter("password");
 
   String kind =null;
   //接收用户级别
   kind=req.getParameter("kind");
   //调用getPassword方法，获取数据库中查询出来的密码
   String temp =getPassword(req,res,id,kind);
   //对比查询出的密码和用户输入的密码是否匹配
   if( password.equals(temp))
   //密码输入正确，调用goo方法
   goo(req,res,kind);
   else {
   //密码输入错误
   message="用户名或密码有误！";
   doError(req,res,message)	;
 	}
 	} 
  //根据用户的级别，分别转向不同的页面
public void goo(HttpServletRequest req, HttpServletResponse res,String kind)
throws ServletException,IOException
{
    //转向学生功能页面
	if(kind.equals("student")) {	
	RequestDispatcher rd = getServletContext().getRequestDispatcher("/student.jsp");
    rd.forward(req, res);}
    //转向教师功能页面
    if(kind.equals("teacher")){
    	RequestDispatcher rd = getServletContext().getRequestDispatcher("/teacher.jsp");
    rd.forward(req, res);}
    //转向管理员功能页面
    if(kind.equals("admin")){
    	RequestDispatcher rd = getServletContext().getRequestDispatcher("/admin.jsp");
    rd.forward(req, res);}
	}
	

  
   //根据用户的级别和输入的用户名，查询对应的密码  
  public String getPassword(HttpServletRequest req, HttpServletResponse res,
                        String id,String kind)
                        throws ServletException, IOException {
   //声明数据库连接类sqlBean的实例
   sqlBean db= new sqlBean();                  	
   String pw="";                     	                     	
   String sql="select password from "+kind+" where id='"+id+"'";
   try{
	//进行数据库查询操作
   ResultSet rs=db.executeQuery(sql); 	
   if(rs.next() ){
     pw= rs.getString("password");
   	}
   	} 
   	catch(Exception e)
{ System.out.print(e.toString());}   	    
    return pw; 
                            }
     
     	
     //处理错误页面
     public void doError(HttpServletRequest req,
                      HttpServletResponse res,
                      String str)
                      throws ServletException, IOException {

    req.setAttribute("problem", str);
    RequestDispatcher rd = getServletContext().getRequestDispatcher("/errorpage.jsp");
    rd.forward(req, res);
  }
  
//   响应get请求
  public void doGet(HttpServletRequest req, HttpServletResponse res)
    throws ServletException, IOException {
    	 String action = action = req.getParameter("action");
//    	检查用户请求参数中是否包含退出参数，如果包含则转向系统的首页面
      if ("logout".equalsIgnoreCase(action)) {
      HttpSession session=req.getSession(true);
        session.invalidate();
        RequestDispatcher rd = getServletContext().getRequestDispatcher("/login.jsp");
        rd.forward(req, res);
    } }
  
}