后台验证码

废话不多说，直接上代码。先看看文件的位置

ValidateCodeServlet.java

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.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/** * Servlet implementation class ValidataCoed */@WebServlet("/ValidataCoed")public class ValidateCodeServlet extends HttpServlet {    private static final long serialVersionUID = 1L;    /**     * @see HttpServlet#HttpServlet()     */    public ValidateCodeServlet() {        super();        // TODO Auto-generated constructor stub    }    /**     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)     */    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        // TODO Auto-generated method stub        this.doPost(request, response);    }    public  Color getRandomColor(int fc,int bc){        Random random = new Random();        Color randomColor = null;        if(fc>255) fc=255;        if(bc>255) bc=255;        //设置个0-255之间的随机颜色值        int r=fc+random.nextInt(bc-fc);        int g=fc+random.nextInt(bc-fc);        int b=fc+random.nextInt(bc-fc);        randomColor = new Color(r,g,b);        return randomColor;//返回具有指定红色、绿色和蓝色值的不透明的 sRGB 颜色    }    /**     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)     */    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        // TODO Auto-generated method stub        //禁止页面缓存        response.setHeader("Pragma", "No-cache");        response.setHeader("Cache-Control", "No-cache");        response.setDateHeader("Expires", 0);        response.setContentType("image/jpeg");      //设置响应正文的MIME类型为图片        int width=60, height=20;          /**创建一个位于缓存中的图像，宽度60，高度20 */          BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);             Graphics g = image.getGraphics();           //获取用于处理图形上下文的对象，相当于画笔        Random random = new Random();               //创建生成随机数的对象        g.setColor(getRandomColor(200,250));        //设置图像的背景色        g.fillRect(0, 0, width, height);            //画一个矩形 ，坐标（0，0），宽度60，高度20         g.setFont(new Font("Times New Roman",Font.PLAIN,18));   //设定字体格式        g.setColor(getRandomColor(160,200));        for(int i=0;i<130;i++){                     //产生130条随机干扰线            int x = random.nextInt(width);               int y = random.nextInt(height);               int xl = random.nextInt(12);               int yl = random.nextInt(12);               g.drawLine(x,y,x+xl,y+yl);              //在图象的坐标（x,y）和坐标（x+x1,y+y1）之间画干扰线         }         String strCode="";          for (int i=0;i<4;i++){               String strNumber=String.valueOf(random.nextInt(10)); //把随机数转换成String字符串            strCode=strCode+strNumber;            //设置字体的颜色            g.setColor(new Color(15+random.nextInt(120),15+random.nextInt(120),15+random.nextInt(120)));            g.drawString(strNumber,13*i+6,16);       //将验证码依次画到图像上,坐标（x=13*i+6,y=16）        }        request.getSession().setAttribute("Code",strCode);          //把验证码保存到Session中           g.dispose();  //释放此图像的上下文以及它使用的所有系统资源        ImageIO.write(image, "JPEG", response.getOutputStream());   //输出JPEG格式的图像            response.getOutputStream().flush();                         //刷新输出流         response.getOutputStream().close();                         //关闭输出流     }}

配置的XML是在上一篇的基础上进行的配置：

<?xml version="1.0" encoding="GBK"?><web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">  <display-name>MyBlog</display-name>  <servlet>    <servlet-name>RegServlet</servlet-name>    <servlet-class>servlet.RegServlet</servlet-class>  </servlet>  <servlet-mapping>    <servlet-name>RegServlet</servlet-name>    <url-pattern>/RegServlet</url-pattern>  </servlet-mapping>  <servlet>  <servlet-name>ValidateCodeServlet</servlet-name>  <servlet-class>servlet.ValidateCodeServlet</servlet-class>  </servlet>  <servlet-mapping>  <servlet-name>ValidateCodeServlet</servlet-name>  //这里的url将会是后面验证码的src的来源  <url-pattern>/ValidateCodeServlet</url-pattern>  </servlet-mapping></web-app>

index.jsp

//在上次的基础上添加了两行代码：<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>府城的博客</title></head><body>    <form action ="RegServlet" method="Post" onsubmit="return reg(this);">        <table align="center" border="0", width="500">        <tr>           <td align ="right" width ="30%">用户名:</td>           <td><input type ="text" name ="username" class="box"></td>                   </tr>         <tr>           <td align ="right" width ="30%">密码:</td>           <td><input type ="text" name ="password" class="box"></td>                   </tr>         <tr>           <td align ="right" width ="30%">性别:</td>           <td><input type ="radio" name ="sex" value="男" checked="checked">男           <input type ="radio" name ="sex" value="女" >女</td>                   </tr>         <tr>           <td align ="right" width ="30%">密码找回问题:</td>           <td><input type ="text" name ="question" class="box"></td>                   </tr>        <tr>           <td align ="right" width ="30%">密码找回答案:</td>           <td><input type ="text" name ="answer" class="box"></td>                   </tr>        <tr>           <td align ="right" width ="30%">邮箱:</td>           <td><input type ="text" name ="email" class="box"></td>                   </tr>         <tr>                <td>验证码：</td>                <td>                    <img alt="" src="ValidateCodeServlet" >                </td>            </tr>            <tr>                <td>输入验证码：</td>                <td>                    <input type="text" name="code"/>                </td>            </tr>        <tr>            <td colspan="2" align="center" height="40">            <input type ="submit" value="注册">            <input type ="reset" value="重置">            </td>        </tr> </body></html>

然后就成功了

这里我没有加验证输入的正确性，很简单的逻辑就不说了。以及如何将四位数字验证码变成字母加数字，无非是ASCLL码的范围。