在页面上生成动态图片验证码

这两种方式都得把验证码存入session当中,然后提交表单时进行才能进行校验,因为都是以img src 方式生成的图片验证码,没法在前台进行验证,或许是我不会,有人想到解决办法的麻烦告我一声.

 

1.引入jsp方式

先创建一个jsp文件,下面这段jsp,其实就是在jsp上写java代码来画一个验证码图片,然后把生成的验证码存入session当中,然后在后台就可以通过session来获取到验证码进行验证.

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ page import="java.util.Random"%>
<%@ page import="java.io.OutputStream"%>
<%@ page import="java.awt.Color"%>
<%@ page import="java.awt.Font"%>
<%@ page import="java.awt.Graphics"%>
<%@ page import="java.awt.image.BufferedImage"%>
<%@ page import="javax.imageio.ImageIO"%>
<%
   int width = 80;
   int height = 32;
   //create the image
   BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
   Graphics g = image.getGraphics();
   // set the background color
   g.setColor(new Color(0xDCDCDC));
   g.fillRect(0, 0, width, height);
   // draw the border
   g.setColor(Color.black);
   g.drawRect(0, 0, width - 1, height - 1);
   // create a random instance to generate the codes
   Random rdm = new Random();
   String hash1 = Integer.toHexString(rdm.nextInt());
   // make some confusion
   for (int i = 0; i < 50; i++) {
      int x = rdm.nextInt(width);
      int y = rdm.nextInt(height);
      g.drawOval(x, y, 0, 0);
   }
   // generate a random code
   String capstr = hash1.substring(0, 4);
   session.setAttribute("key", capstr);    //把生成的验证码存入session当中
   g.setColor(new Color(0, 100, 0));
   g.setFont(new Font("Candara", Font.BOLD, 24));
   g.drawString(capstr, 8, 24);
   g.dispose();
   response.setContentType("image/jpeg");
   out.clear();
   out = pageContext.pushBody();
   OutputStream strm = response.getOutputStream();
   ImageIO.write(image, "jpeg", strm);
   strm.close();
%>

这个就是img标签,只需要把src里面的路径改为上面jsp存放的路径就可以了,单击事件是为了每次点击图片生成新的验证码.

<img style="height: 100%;width: 100%" id="loginform:vCode" src="${pageContext.request.contextPath }/jsps/validatecode.jsp" onclick="javascript:document.getElementById('loginform:vCode').src='${pageContext.request.contextPath }/jsps/validatecode.jsp?'+Math.random();" />

 2.通过访问controller方式在后台生成图片验证码来写到前台

先写两个工具类

生成随机数的

package com.bgs.utils;

public class RandomNumberUtil {

    public static String getRandomNumber4(){
        String code = "";
        for(int i=0;i<4;i++){
            int random = (int)(Math.random()*10);
            code += String.valueOf(random);
        }
        return code;
    }

    public static String getRandomNumber6(){
        String code = "";
        for(int i=0;i<6;i++){
            int random = (int)(Math.random()*10);
            code += String.valueOf(random);
        }
        return code;
    }
}

生成图片的  这个生成图片的需要传入一个字符串进去

package com.bgs.utils;

import java.awt.*;
import java.awt.image.BufferedImage;
import java.util.Random;

public class ImageVerifyCodeUtil {

    public static BufferedImage getBufferedImage(String capstr){
        int width = 80;
        int height = 32;
        //create the image
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        Graphics g = image.getGraphics();
        // set the background color
        g.setColor(new Color(0xDCDCDC));
        g.fillRect(0, 0, width, height);
        // draw the border
        g.setColor(Color.black);
        g.drawRect(0, 0, width - 1, height - 1);
        g.setColor(new Color(0, 100, 0));
        g.setFont(new Font("Candara", Font.BOLD, 24));
        g.drawString(capstr, 8, 24);
        g.dispose();
        return image;
    }


}

 controller

//生成图片验证码的方法
@RequestMapping("/findVerifyPictureCode")
public void findVerifyPictureCode(HttpSession session, HttpServletResponse response){
    //告诉客户端，输出的格式
    response.setContentType("image/jpeg");
    String randomNumber4 = RandomNumberUtil.getRandomNumber4();    //生成随机数
    BufferedImage bufferedImage = ImageVerifyCodeUtil.getBufferedImage(randomNumber4);  把随机数传入生成图片
    try {
        ImageIO.write(bufferedImage, "JPG", response.getOutputStream());  //把图片写回到前台
        session.setAttribute("randomCode",randomNumber4);     //将生成的验证码存入session
    } catch (IOException e) {
        e.printStackTrace();
    }

} 

前台代码,记得把src中的路径改为访问controller的路径

<img id="servletImg" src="${pageContext.request.contextPath}/managerUser/findVerifyPictureCode" onclick="javascript:changImg()"/>

<script type="text/javascript">
    function changImg(){
        var img = document.getElementById("servletImg");
        var d = new Date();
        var time = d.getTime();//如果没有这个
        //下面这一句不会起作用，因为浏览器的缓存技术，图片并不会刷新
        //img.src="/myHelloWeb/servlet/ImageServlet";
        img.src="${pageContext.request.contextPath}/managerUser/findVerifyPictureCode?"+time;
        //?号后面的东西是通过get方式传递的
    }

</script>