本文共 5307 字，大约阅读时间需要 17 分钟。

两个servlet文件

import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;import java.io.IOException;@WebServlet("/loginServlet")public class LoginServlet extends HttpServlet {    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        //1.设置request编码        request.setCharacterEncoding("utf-8");        //2.获取参数        String username = request.getParameter("username");        String password = request.getParameter("password");        String checkCode = request.getParameter("checkCode");        //3.先获取生成的验证码        HttpSession session = request.getSession();        String checkCode_session = (String) session.getAttribute("checkCode_session");        //删除session中存储的验证码        session.removeAttribute("checkCode_session");        //3.先判断验证码是否正确        if(checkCode_session!= null && checkCode_session.equalsIgnoreCase(checkCode)){            //忽略大小写比较            //验证码正确            //判断用户名和密码是否一致            if("zhangsan".equals(username) && "123".equals(password)){//需要调用UserDao查询数据库                //登录成功                //存储信息，用户信息                session.setAttribute("user",username);                //重定向到success.jsp                response.sendRedirect(request.getContextPath()+"/success.jsp");            }else{                //登录失败                //存储提示信息到request                request.setAttribute("login_error","用户名或密码错误");                //转发到登录页面                request.getRequestDispatcher("/login.jsp").forward(request,response);            }        }else{            //验证码不一致            //存储提示信息到request            request.setAttribute("cc_error","验证码错误");            //转发到登录页面            request.getRequestDispatcher("/login.jsp").forward(request,response);        }    }    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        this.doPost(request, response);    }}

2.CheckCodeServlet.java

import javax.imageio.ImageIO;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import java.awt.*;import java.awt.image.BufferedImage;import java.io.IOException;import java.util.Random;@WebServlet("/checkCodeServlet")public class CheckCodeServlet extends HttpServlet {    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        int width = 100;        int height = 50;        //1.创建一对象，在内存中图片(验证码图片对象)        BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);        //2.美化图片        //2.1 填充背景色        Graphics g = image.getGraphics();//画笔对象        g.setColor(Color.PINK);//设置画笔颜色        g.fillRect(0,0,width,height);        //2.2画边框        g.setColor(Color.BLUE);        g.drawRect(0,0,width - 1,height - 1);        String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghigklmnopqrstuvwxyz0123456789";        //生成随机角标        Random ran = new Random();        StringBuilder sb = new StringBuilder();        for (int i = 1; i <= 4; i++) {            int index = ran.nextInt(str.length());            //获取字符            char ch = str.charAt(index);//随机字符            sb.append(ch);            //2.3写验证码            g.drawString(ch+"",width/5*i,height/2);        }        String checkCode_session = sb.toString();        //将验证码存入session        request.getSession().setAttribute("checkCode_session",checkCode_session);        //2.4画干扰线        g.setColor(Color.GREEN);        //随机生成坐标点        for (int i = 0; i < 10; i++) {            int x1 = ran.nextInt(width);            int x2 = ran.nextInt(width);            int y1 = ran.nextInt(height);            int y2 = ran.nextInt(height);            g.drawLine(x1,y1,x2,y2);        }        //3.将图片输出到页面展示        ImageIO.write(image,"jpg",response.getOutputStream());    }    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        this.doPost(request,response);    }}

3.登录页面login.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>                
   
        
    
                 
      
                       
用户名
                       
                  
                  
                       
密码
                       
                  
                  
                       
验证码
                       
                  
                  
                       
                  
                  
                       
                  
             
    
    
   
    
   
    <%=request.getAttribute("cc_error") == null ? "" : request.getAttribute("cc_error")%>
   
    
   
    <%=request.getAttribute("login_error") == null ? "" : request.getAttribute("login_error") %>
   

4.登录成功跳转页面

<%--  Created by IntelliJ IDEA.  User: wuhh  Date: 2020/6/6  Time: 19:01  To change this template use File | Settings | File Templates.--%><%@ page contentType="text/html;charset=UTF-8" language="java" %>        
<%=request.getSession().getAttribute("user")%>欢迎您！！！

页面效果

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