前端界面实现（由于验证码是动态获取所以用jsp格式）

<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%>
              ${msg}       
     
       
      
       
       
请登录！
                   用户名：
       
       
       
                   密   码: 
       
       
       
       
       
          看不清，换一张！
       
       
       验证码：
              
       
       
       
              
               
      
       
     
           

用于验证码图片所编写的工具类

package com.sxt.mvcpro.util;import java.awt.Color;import java.awt.Font;import java.awt.Graphics;import java.awt.image.BufferedImage;import java.io.ByteArrayOutputStream;import java.io.IOException;import java.util.Random;import javax.imageio.ImageIO;import javax.servlet.ServletException;import javax.servlet.ServletOutputStream;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;@WebServlet("/imgCode")public class RandomCode extends HttpServlet {    private static final long serialVersionUID = 1L;    private static int WIDTH = 102;//定义验证图片的宽度    private static int HEIGHT = 50;//定义验证图片的高度    public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        HttpSession session = request.getSession();        response.setContentType("image/jpeg");        ServletOutputStream sos = response.getOutputStream();        response.setHeader("Pragma", "No-cache");        response.setHeader("Cache-Control", "no-cache");        response.setDateHeader("Expires", 0);        BufferedImage image = new BufferedImage(WIDTH, HEIGHT,                BufferedImage.TYPE_INT_RGB);        Graphics g = image.getGraphics();        char[] rands = generateCheckCode();        drawBackground(g);        drawRands(g, rands);        g.dispose();        ByteArrayOutputStream bos = new ByteArrayOutputStream();        ImageIO.write(image, "JPEG", bos);        byte[] buf = bos.toByteArray();        response.setContentLength(buf.length);        sos.write(buf);  //锟斤拷锟斤拷锟缴碉拷锟斤拷证锟斤拷图片写锟斤拷页锟斤拷        bos.close();        sos.close();        //锟斤拷锟斤拷锟缴碉拷锟斤拷证锟诫保锟芥到session        session.setAttribute("rand", new String(rands));    }    private void drawBackground(Graphics g) {        g.setColor(new Color(0xDCDCDC));        g.fillRect(0, 0, WIDTH, HEIGHT);        for (int i = 0; i < 120; i++) {            int x = (int) (Math.random() * WIDTH);            int y = (int) (Math.random() * HEIGHT);            int red = (int) (Math.random() * 255);            int green = (int) (Math.random() * 255);            int blue = (int) (Math.random() * 255);            g.setColor(new Color(red, green, blue));            g.drawOval(x, y, 1, 0);        }    }    private void drawRands(Graphics g, char[] rands) {        // g.setColor(Color.BLUE);        Random random = new Random();        int red = random.nextInt(110);        int green = random.nextInt(50);        int blue = random.nextInt(50);        g.setColor(new Color(red, green, blue));        g.setFont(new Font(null, Font.ITALIC | Font.BOLD, 30));        g.drawString("" + rands[0], 5, 35);        g.drawString("" + rands[1], 25, 34);        g.drawString("" + rands[2], 45, 36);        g.drawString("" + rands[3], 65, 33);    }    private char[] generateCheckCode() {        String chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";        char[] rands = new char[4];        for (int i = 0; i < 4; i++) {            int rand = (int) (Math.random() * 36);            rands[i] = chars.charAt(rand);        }        return rands;    }    public void doPost(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        this.doGet(request, response);    }}

servlet层代码编写

@Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {    String username=req.getParameter("username");    String pwd=req.getParameter("pwd");    String ranCode=req.getParameter("code");    //先判断验证码是否正确    if (ranCode.equalsIgnoreCase((String)req.getSession().getAttribute("rand"))) {        if ("smith".equals(username)&&"1234".equals(pwd)) {            req.getSession().setAttribute("name", username);            //跳转到首页            resp.sendRedirect("/Mvcpro/pages/welcome.jsp");        }else {            req.setAttribute("msg", "用户名密码不正确！");            req.getRequestDispatcher("/pages/login.jsp").forward(req, resp);        }    }}@Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        this.doGet(req, resp);    }

总的来说借助所编写的工具类控制层的代码相对变得比较简洁，可塑性强，在工具类花的时间会较多，可以直接调用，后期与其他页面相结合也较为方便。