Java验证码功能的实现方法

时间:2022-11-19 17:22:37

一、前言

      验证码可以说在我们生活中已经非常普遍了,任何一个网站,任何一个App都会有这个功能,但是为啥要有这个呢?如何做才能做出来呢?下面小编会带领大家一起用java完成一个验证码的功能。

二、验证码的作用

      一般可以防止有人利用机器人自动批量注册、对特定的注册用户用特定程序暴力破解方式进行不断的登录,灌水。因为验证码是一个混合了数字和符号的图片,人眼看起来都费劲,机器识别起来就更难了。

三、java实现

Java验证码功能的实现方法

3.1 建立验证码的servlet 类:

 

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package com.bjpowernode.drp.util.servlet;
 
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
 
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
/**
 * 验证码功能生成
 * @author Ares
 *
 */
public class AuthImage extends HttpServlet{
     private static final String CONTENT_TYPE = "text/html; charset=gb2312";
      //设置字母的大小,大小
      private Font mFont = new Font("Times New Roman", Font.PLAIN, 17);
      public void init() throws ServletException
      {
        super.init();
      }
      Color getRandColor(int fc,int bc)
      {
        Random random = new Random();
        if(fc>255) fc=255;
        if(bc>255) bc=255;
        int r=fc+random.nextInt(bc-fc);
        int g=fc+random.nextInt(bc-fc);
        int b=fc+random.nextInt(bc-fc);
        return new Color(r,g,b);
      }
 
      public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
      {
        response.setHeader("Pragma","No-cache");
        response.setHeader("Cache-Control","no-cache");
        response.setDateHeader("Expires", 0);
        //表明生成的响应是图片
        response.setContentType("image/jpeg");
 
        int width=100, height=18;
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
 
        Graphics g = image.getGraphics();
        Random random = new Random();
        g.setColor(getRandColor(200,250));
        g.fillRect(1, 1, width-1, height-1);
        g.setColor(new Color(102,102,102));
        g.drawRect(0, 0, width-1, height-1);
        g.setFont(mFont);
 
        g.setColor(getRandColor(160,200));
 
        //画随机线
        for (int i=0;i<155;i++)
        {
          int x = random.nextInt(width - 1);
          int y = random.nextInt(height - 1);
          int xl = random.nextInt(6) + 1;
          int yl = random.nextInt(12) + 1;
          g.drawLine(x,y,x + xl,y + yl);
        }
 
        //从另一方向画随机线
        for (int i = 0;i < 70;i++)
        {
          int x = random.nextInt(width - 1);
          int y = random.nextInt(height - 1);
          int xl = random.nextInt(12) + 1;
          int yl = random.nextInt(6) + 1;
          g.drawLine(x,y,x - xl,y - yl);
        }
 
        //生成随机数,并将随机数字转换为字母
        String sRand="";
        for (int i=0;i<6;i++)
        {
          int itmp = random.nextInt(26) + 65;
          char ctmp = (char)itmp;
          sRand += String.valueOf(ctmp);
          g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));
          g.drawString(String.valueOf(ctmp),15*i+10,16);
        }
 
        HttpSession session = request.getSession(true);
        session.setAttribute("rand",sRand);
        g.dispose();
        ImageIO.write(image, "JPEG", response.getOutputStream());
      }
      public void destroy()
      {
      }
}

3.2 在WEB-INF文件下的web.xml配置servlet

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//servlet名字和位置
<servlet>
  <servlet-name>AuthImage</servlet-name>
  <servlet-class>com.bjpowernode.drp.util.servlet.AuthImage</servlet-class>
</servlet>
//servlet 对那些映射起作用
<servlet-mapping>
  <servlet-name>AuthImage</servlet-name>
  <url-pattern>/servlet/login/AuthImage</url-pattern>
</servlet-mapping>

3.3 前台调用Servlet

jsp代码:

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<img id="img" style="cursor:pointer;" alt="验证码" src="${pageContext.request.contextPath}/servlet/login/AuthImage" onclick="changeImg()">

js:

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//点击验证码变换图片
function changeImg(){
  var img =document.getElementById("img");
  img.src="${pageContext.request.contextPath}/servlet/login/AuthImage?d="+Math.random();
  return false;
}

四、小结

      通过这次的对验证码的学习,自己也是有了一定的认识,对整个Servlet和前台代码之间的交互,数据传输也有了很好地提升,所以以后还是要多多的学习一下这些的技巧,多多总结一下。这样知识才会扎实。

以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持服务器之家。

原文链接:http://blog.csdn.net/kisscatforever/article/details/54929657