javaweb中使用servlet实现验证码

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1、jsp页面

在jsp页面中，我们要有下面几部分：1.输入框2.验证码图片3.看不清按钮4.提交按钮

预期效果：

思路：

2、jsp页面代码：

<%@ page language="java" import="java.util.*" contentType="text/html; charset=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">    <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">    -->    <script type="text/javascript">    //reloadCode方法：实现"点击看不清刷新"的功能            function reloadCode(){                //time变量的功能是强制刷新，忽略浏览器的缓存机制                var time = new Date().getTime();                document.getElementById("imagecode").src="<%=request.getContextPath() %>/servlet/servletImage?d="+time;//传进的time变量，因为time在变化，所以url也在变化，因此可以说是强制刷新            }    </script>  </head>  <body>  <!--表单的方式跳转到loginservlet-->  <form action="<%=request.getContextPath() %>/servlet/loginservlet" method = "get">        验证码：<input type="text" name="checkcode"/>        <img alt="验证码" id="imagecode" src="<%=request.getContextPath() %>/servlet/servletImage"><!--src的方式实现链接到servletImage-->        <a href="javascript: reloadCode();">看不清楚，换一张！</a>        <input type="submit" value="提交" />  </form>  </body></html>

3、servletImage

该servlet实现的主要功能是描绘出验证码的图片，里面随机画出4个字母与数字的组合，因为在jsp页面中只用到了get方法跳转，所以重写servlet中的doget方法。

package servlet;import java.awt.Color;import java.awt.Graphics;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.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class servletImage extends HttpServlet {    /**     * Constructor of the object.     */    public servletImage() {        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 {            //验证码是通过img标签触发的，所以是get方式，重写servlet方法：        /*         * BufferedImage(int width, int height, int imageType)                                  构建了一个 BufferedImage一个预定义的图像类型。            TYPE_INT_RGB  代表8位RGB分量包装成整数像素的图像。                                */        BufferedImage bi = new BufferedImage(68,22,BufferedImage.TYPE_INT_RGB);        Graphics g = bi.getGraphics();        Color c = new Color(200,150,255);        g.setColor(c);//背景颜色        g.fillRect(0, 0, 68, 22);//背景框        //字母数字组合：        char[] ch = "ABCDEFGHIJKLMNOPQRSTUVEXYZ123456789".toCharArray();        Random r = new Random();        int len = ch.length;        int index;        StringBuffer sb = new StringBuffer();        for(int i =0;i<4;i++){            index = r.nextInt(len);//随机获得一个起始位置            g.setColor(new Color(r.nextInt(88),r.nextInt(188),r.nextInt(255)));//给字体一个随机的颜色            g.drawString(ch[index]+"", (i*15)+3, 18);            sb.append(ch[index]);        }        request.getSession().setAttribute("piccode", sb.toString());//将生产的验证码保存下来，以便之后的检验输入是否一致        ImageIO.write(bi,"JPG",response.getOutputStream());    }    /**     * 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.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");        out.println("<HTML>");        out.println("  <HEAD><TITLE>A Servlet</TITLE></HEAD>");        out.println("  <BODY>");        out.print("    This is ");        out.print(this.getClass());        out.println(", using the POST method");        out.println("  </BODY>");        out.println("</HTML>");        out.flush();        out.close();    }    /**     * Initialization of the servlet. <br>     *     * @throws ServletException if an error occurs     */    public void init() throws ServletException {        // Put your code here    }}

4、loginServlet

该servlet主要实现验证输入的验证码和之前的图片上的验证码是否一致，之前的图片上的验证码保存在了session中

package servlet;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class loginservlet extends HttpServlet {    /**     * Constructor of the object.     */    public loginservlet() {        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 {            //首先获得之前保存在session中的验证码            String piccode = (String) request.getSession().getAttribute("piccode");            String checkcode = request.getParameter("checkcode");            response.setContentType("text/html;charset =UTF-8");            PrintWriter out = response.getWriter();            //response.setContentType("text/html;charset =UTF-8");            if(checkcode.equals(piccode)){                out.print("输入正确");            }else{                out.print("输入不正确！");            }            out.flush();            out.close();    }    /**     * 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.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");        out.println("<HTML>");        out.println("  <HEAD><TITLE>A Servlet</TITLE></HEAD>");        out.println("  <BODY>");        out.print("    This is ");        out.print(this.getClass());        out.println(", using the POST method");        out.println("  </BODY>");        out.println("</HTML>");        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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