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:
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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:
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<%@ 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:
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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):
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<%@ 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:
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。