java web验证码实现代码分享

2019-11-26 14:10:06

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验证码的作用：通常的登录或者注册系统时，都会要求用户输入验证码，以此区别用户行为和计算机程序行为，目的是有人防止恶意注册、暴力破解密码等。

实现验证码的思路：用 server 实现随机生成数字和字母组成图片的功能，用 jsp 页面实现显示验证码和用户输入验证码的功能，再用 server 类分别获取图片和用户输入的数据，判断两个数据是否一致。
代码实现

1.编写数字、英文随机生成的 server 类，源码：

package com;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.io.PrintWriter;import javax.imageio.ImageIO;import javax.servlet.ServletException;import javax.servlet.ServletOutputStream;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;public class logcheck extends HttpServlet { public logcheck() {  super(); }  public void destroy() {  super.destroy();  } public void doGet(HttpServletRequest request, HttpServletResponse response)   throws ServletException, IOException {  doPost(request, response); } /*实现的核心代码*/ public void doPost(HttpServletRequest request, HttpServletResponse response)   throws ServletException, IOException {  response.setContentType("image/jpeg");  HttpSession session=request.getSession();  int width=60;  int height=20;    //设置浏览器不要缓存此图片  response.setHeader("Pragma", "No-cache");  response.setHeader("Cache-Control", "no-cache");  response.setDateHeader("Expires", 0);    //创建内存图像并获得图形上下文  BufferedImage image=new BufferedImage(width, height,BufferedImage.TYPE_INT_RGB);  Graphics g=image.getGraphics();    /*   * 产生随机验证码   * 定义验证码的字符表   */  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);  }    /*   * 产生图像   * 画背景   */  g.setColor(new Color(0xDCDCDC));  g.fillRect(0, 0, width, height);    /*   * 随机产生120个干扰点   */    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);  }  g.setColor(Color.BLACK);  g.setFont(new Font(null, Font.ITALIC|Font.BOLD,18));    //在不同高度输出验证码的不同字符  g.drawString(""+rands[0], 1, 17);  g.drawString(""+rands[1], 16, 15);  g.drawString(""+rands[2], 31, 18);  g.drawString(""+rands[3], 46, 16);  g.dispose();    //将图像传到客户端  ServletOutputStream sos=response.getOutputStream();  ByteArrayOutputStream baos=new ByteArrayOutputStream();  ImageIO.write(image, "JPEG", baos);  byte[] buffer=baos.toByteArray();  response.setContentLength(buffer.length);  sos.write(buffer);  baos.close();  sos.close();    session.setAttribute("checkcode", new String(rands)); }  public void init() throws ServletException {  // Put your code here }}

2.用于显示验证码的页面：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head>  <base href="<%=basePath%>">    <title>index</title>  <meta http-equiv="pragma" content="no-cache">  <meta http-equiv="cache-control" content="no-cache">  <meta http-equiv="expires" content="0">    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">  <meta http-equiv="description" content="This is my page">  <!--  <link rel="stylesheet" type="text/css" href="styles.css">  --> </head>  <body> <form action="yanzheng" method="post">   <input type="text" name="name" size="5" maxlength="4">  <a href="index.jsp"><img border="0" src="logcheck"></a><br><br>       <input type="submit" value="提交"> </form> </body></html>

3.用于检验输入的验证码是否正确：

package com;import java.io.IOException;import java.io.PrintWriter;import javax.jms.Session;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;public class yanzheng extends HttpServlet { public yanzheng() {  super(); } public void destroy() {  super.destroy();  } public void doGet(HttpServletRequest request, HttpServletResponse response)   throws ServletException, IOException {  doPost(request, response); } /*核心代码*/ public void doPost(HttpServletRequest request, HttpServletResponse response)   throws ServletException, IOException {  String info=null;  /*获取输入的值*/  String value1=request.getParameter("name");  /*获取图片的值*/  HttpSession session=request.getSession();  String value2=(String)session.getAttribute("checkcode");  /*对比两个值（字母不区分大小写）*/  if(value2.equalsIgnoreCase(value1)){   info="验证码输入正确";  }else{   info="验证码输入错误";  }  System.out.println(info);  request.setAttribute("info", info);  request.getRequestDispatcher("/login.jsp").forward(request, response); }  public void init() throws ServletException {  // Put your code here }}

4.显示输入结构界面（输入验证码是否正确）：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <base href="<%=basePath%>">  <title>My JSP 'login.jsp' starting page</title>  <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0">  <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="This is my page"> <!-- <link rel="stylesheet" type="text/css" href="styles.css"> --> </head>  <body> <%=request.getAttribute("info") %> </body></html>

5.项目结构、效果截图：