SSM 实现登录验证码功能（附源码）

package com.utils;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.util.Random;
import javax.imageio.ImageIO;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class RandomValidateCode {
 public static final String RANDOMCODEKEY = "randomcode_key";//放到session中的key
 private Random random = new Random();
 private String randString = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";//随机产生的字符串
 private int width = 80;//图片宽
 private int height = 26;//图片高
 private int lineSize = 40;//干扰线数量
 private int stringNum = 4;//随机产生字符数量
 /**
  * 生成随机图片
  */
 public void getRandcode(HttpServletRequest request,
   HttpServletResponse response) {
  HttpSession session = request.getSession();
  //BufferedImage类是具有缓冲区的Image类,Image类是用于描述图像信息的类
  BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_BGR);
  //产生Image对象的Graphics对象,改对象可以在图像上进行各种绘制操作
  Graphics g = image.getGraphics();
  g.fillRect(0, 0, width, height);
  g.setFont(new Font("Times New Roman",Font.ROMAN_BASELINE,18));
  g.setColor(getRandColor(160, 200));
  //绘制干扰线
  for(int i=0;i<=lineSize;i++){
   drowLine(g);
  }
  //绘制随机字符
  String randomString = "";
  for(int i=1;i<=stringNum;i++){
   randomString=drowString(g,randomString,i);
  }
  session.removeAttribute(RANDOMCODEKEY);
  session.setAttribute(RANDOMCODEKEY, randomString);
  g.dispose();
  try {
   //将内存中的图片通过流动形式输出到客户端
   ImageIO.write(image, "JPEG", response.getOutputStream());
  } catch (Exception e) {
   e.printStackTrace();
  }
 }
 /*
  * 获得字体
  */
 private Font getFont(){
  return new Font("Fixedsys",Font.CENTER_BASELINE,18);
 }
 /*
  * 获得颜色
  */
 private Color getRandColor(int fc,int bc){
  if(fc > 255)
   fc = 255;
  if(bc > 255)
   bc = 255;
  int r = fc + random.nextInt(bc-fc-16);
  int g = fc + random.nextInt(bc-fc-14);
  int b = fc + random.nextInt(bc-fc-18);
  return new Color(r,g,b);
 }
 /*
  * 绘制字符串
  */
 private String drowString(Graphics g,String randomString,int i){
  g.setFont(getFont());
  g.setColor(new Color(random.nextInt(101),random.nextInt(111),random.nextInt(121)));
  String rand = String.valueOf(getRandomString(random.nextInt(randString.length())));
  randomString +=rand;
  g.translate(random.nextInt(3), random.nextInt(3));
  g.drawString(rand, 13*i, 16);
  return randomString;
 }
 /*
  * 绘制干扰线
  */
 private void drowLine(Graphics g){
  int x = random.nextInt(width);
  int y = random.nextInt(height);
  int xl = random.nextInt(13);
  int yl = random.nextInt(15);
  g.drawLine(x, y, x+xl, y+yl);
 }
 /*
  * 获取随机的字符
  */
 public String getRandomString(int num){
  return String.valueOf(randString.charAt(num));
 }
}

 /**
 * 获取生成验证码显示到 UI 界面
 * @param request
 * @param response
 * @throws ServletException
 * @throws IOException
 */
 @RequestMapping(value="/checkCode")
 public void checkCode(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {
 //设置相应类型,告诉浏览器输出的内容为图片
  response.setContentType("image/jpeg");
  //设置响应头信息，告诉浏览器不要缓存此内容
  response.setHeader("pragma", "no-cache");
  response.setHeader("Cache-Control", "no-cache");
  response.setDateHeader("Expire", 0);
  RandomValidateCode randomValidateCode = new RandomValidateCode();
  try {
   randomValidateCode.getRandcode(request, response);//输出图片方法
  } catch (Exception e) {
   e.printStackTrace();
  }
 }

<img src="checkCode" alt="" width="100" height="32" class="passcode" style="height:43px;cursor:pointer;" onclick="this.src=this.src+'?'">