Servlet 自动生成验证码

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Servlet页面

package com.zzu.edu.servlet;import java.awt.Color;import java.awt.Graphics;import java.awt.Image;import java.awt.image.BufferedImage;import java.io.IOException;import java.io.PrintWriter;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;import javax.servlet.http.HttpSession;@WebServlet(name="Captcha", urlPatterns="/Captcha")public class Captcha extends HttpServlet {    /**     * Constructor of the object.     */    public Captcha() {        super();    }    /**     * Destruction of the servlet. <br>     */    public void destroy() {        super.destroy(); // Just puts "destroy" string in log        // Put your code here    }    /**     * The doGet method of the servlet. <br>     *     * This method is called when a form has its tag value method equals to get.     *      * @param request the request send by the client to the server     * @param response the response send by the server to the client     * @throws ServletException if an error occurred     * @throws IOException if an error occurred     */    public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        doPost(request, response);    }    /**     * The doPost method of the servlet. <br>     *     * This method is called when a form has its tag value method equals to post.     *      * @param request the request send by the client to the server     * @param response the response send by the server to the client     * @throws ServletException if an error occurred     * @throws IOException if an error occurred     */    public void doPost(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        request.setCharacterEncoding("utf-8");        response.setCharacterEncoding("utf-8");        HttpSession session = request.getSession();        BufferedImage bi = new BufferedImage(68,22, BufferedImage.TYPE_INT_RGB);        Graphics graphics = bi.getGraphics();        Color color = new Color(200, 150, 255);        graphics.setColor(color);        //设定背景颜色值        graphics.fillRect(0, 0, 68, 22);        char[] ch = "ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890".toCharArray();        //验证码字符集合        StringBuffer sb = new StringBuffer();        Random random = new Random();        Integer length = ch.length, index;        for (int i = 0; i < 4; i++){            index = random.nextInt(length);            //每次从集合中随机取出一个值            graphics.setColor(new Color(random.nextInt(88), random.nextInt(188), random.nextInt(255)));            graphics.drawString(ch[index]+"", (i*15)+3, 18);            sb.append(ch[index]);        }        session.setAttribute("captcha", sb.toString());        //把验证码放在session中，用于后来的验证        ImageIO.write(bi, "JPG", response.getOutputStream());    }    /**     * Initialization of the servlet. <br>     *     * @throws ServletException if an error occurs     */    public void init() throws ServletException {        // Put your code here    }}

jsp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>My JSP 'index.jsp' starting page</title>    <meta http-equiv="pragma" content="no-cache">    <meta http-equiv="cache-control" content="no-cache">  </head>  <body>    <form action="<%=path%>/Login">      验证码：<input type="text" name="captcha" >.  <img id="code" alt="验证码" src="<%=path %>/captcha.jpg" />  <a href="javascript:reloadCode();">看不清</a>  <input type="submit" value="submit" />    </form>  <script type="text/javascript">  function reloadCode(){//用于刷新验证码，      var time = new Date().getTime();      document.getElementById("code").src="<%=path %>/captcha.jpg?time="+time;      //如果地址中不加入time，每次请求的URL是一样的，      //而浏览器中有缓存，不会发起新的请求，      //加time是为了让每次请求的url不一样，这样每次都会发起一些请求  }  </script>  </body></html>

验证页面

package com.zzu.edu.servlet;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;@WebServlet(name="Login", urlPatterns="/Login")public class Login extends HttpServlet {    /**     * Constructor of the object.     */    public Login() {        super();    }    /**     * Destruction of the servlet. <br>     */    public void destroy() {        super.destroy(); // Just puts "destroy" string in log        // Put your code here    }    /**     * The doGet method of the servlet. <br>     *     * This method is called when a form has its tag value method equals to get.     *      * @param request the request send by the client to the server     * @param response the response send by the server to the client     * @throws ServletException if an error occurred     * @throws IOException if an error occurred     */    public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        doPost(request, response);    }    /**     * The doPost method of the servlet. <br>     *     * This method is called when a form has its tag value method equals to post.     *      * @param request the request send by the client to the server     * @param response the response send by the server to the client     * @throws ServletException if an error occurred     * @throws IOException if an error occurred     */    public void doPost(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        response.setContentType("text/html");        PrintWriter out = response.getWriter();        out.print(request.getParameter("captcha") + "    "                + request.getSession().getAttribute("captcha"));                //获取表单中填写的验证码，并也session中存的验证码比较        out.print(request.getParameter("captcha").toUpperCase().equals(((String)request.getSession().getAttribute("captcha")).toUpperCase()));        out.flush();        out.close();    }    /**     * Initialization of the servlet. <br>     *     * @throws ServletException if an error occurs     */    public void init() throws ServletException {        // Put your code here    }}

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