package com.lhy.web.servlet;import java.awt.BasicStroke;import java.awt.Color;import java.awt.Font;import java.awt.Graphics2D;import java.awt.image.BufferedImage;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;import java.io.OutputStream;import java.util.Random;import javax.imageio.ImageIO;public class VerifyCode {        private int w = 70;//图片长        private int h = 35;//图片宽         private Random r = new Random();//Random类 生成随机数          // 列举验证图片中验证码的字体类型     //{"宋体", "华文楷体", "黑体", "华文新魏", "华文隶书", "微软雅黑", "楷体_GB2312"}    private String[] fontNames  = {"宋体", "华文楷体", "黑体", "微软雅黑", "楷体_GB2312"};    // 验证码可选字符    private String codes="23456789abcdefghjkmnopqrstuvwxyzABCDEFGHJKMNPQRSTUVWXYZ";    // 背景色    private Color bgColor  = new Color(255, 255, 255);    // 验证码上的文本    private String text ;            // 生成随机的颜色    private Color randomColor () {            int red = r.nextInt(150);            int green = r.nextInt(150);            int blue = r.nextInt(150);            return new Color(red, green, blue);    }    // 生成随机的字体    private Font randomFont () {                int index = r.nextInt(fontNames.length);                String fontName = fontNames[index];//生成随机的字体名称                int style = r.nextInt(4);//生成随机的样式, 0(无样式), 1(粗体), 2(斜体), 3(粗体+斜体)                int size = r.nextInt(5) + 24; //生成随机字号, 24 ~ 28                return new Font(fontName, style, size);    }    // 画干扰线    private void drawLine (BufferedImage image) {            int num  = 3;//一共画3条            Graphics2D g2 = (Graphics2D)image.getGraphics();            for(int i = 0; i < num; i++) {//生成两个点的坐标，即4个值                int x1 = r.nextInt(w);                int y1 = r.nextInt(h);                int x2 = r.nextInt(w);                int y2 = r.nextInt(h);                 g2.setStroke(new BasicStroke(1.5F));                 g2.setColor(Color.BLUE); //干扰线是蓝色                g2.drawLine(x1, y1, x2, y2);//画线            }    }        // 随机生成一个字符    private char randomChar () {            int index = r.nextInt(codes.length());            return codes.charAt(index);    }        // 创建BufferedImage    private BufferedImage createImage () {            //宽，高，图片的类型            BufferedImage image = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);             Graphics2D g2 = (Graphics2D)image.getGraphics();             g2.setColor(this.bgColor);            g2.fillRect(0, 0, w, h);             return image;    }        // 返回验证码图片上的文本    public String getText () {            return text;    }        // 保存图片到指定的输出流    public static void output (BufferedImage image, OutputStream out)                     throws IOException {            ImageIO.write(image, "JPEG", out);    }        // 调用这个方法得到验证码        public BufferedImage getImage () {                BufferedImage image = createImage();//创建图片缓冲区                 Graphics2D g2 = (Graphics2D)image.getGraphics();//得到绘制环境                StringBuilder sb = new StringBuilder();//用来装载生成的验证码文本                // 向图片中画4个字符                for(int i = 0; i < 4; i++)  {//循环四次，每次生成一个字符                    String s = randomChar() + "";//随机生成一个字母                     sb.append(s); //把字母添加到sb中                    float x = i * 1.0F * w / 4; //设置当前字符的x轴坐标                    g2.setFont(randomFont()); //设置随机字体                    g2.setColor(randomColor()); //设置随机颜色                    g2.drawString(s, x, h-5); //画图                }                this.text = sb.toString(); //把生成的字符串赋给了this.text                drawLine(image); //添加干扰线                return image;                }        public static void main(String[] args) throws FileNotFoundException, IOException {            VerifyCode vc = new VerifyCode();//创建VerifyCode类的对象            BufferedImage bi = vc.getImage();//调用getImge()方法获得一个BufferedImage对象            VerifyCode.output(bi, new FileOutputStream("C:/验证码3.jpg"));//调用静态方法output()方法将图片保存在文件输出流中            System.out.println(vc.getText());//在控制台上打印验证码的文本值        }}

package com.lhy.web.servlet;import java.awt.image.BufferedImage;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class VerifyCodeServlet extends HttpServlet {    public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        /*         * 1. 生成图片         * 2. 保存图片上的文本到session域中         * 3. 把图片响应给客户端         */        VerifyCode vc = new VerifyCode();        BufferedImage image = vc.getImage();        request.getSession().setAttribute("session_vcode", vc.getText());//保存图片上的文本到session域                VerifyCode.output(image, response.getOutputStream());    }}

package com.lhy.web.servlet;import java.io.IOException;import javax.servlet.RequestDispatcher;import javax.servlet.ServletException;import javax.servlet.http.Cookie;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;public class LoginServlet extends HttpServlet {    public void doPost(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        /*         * 校验验证码         * 1. 从session中获取正确的验证码         * 2. 从表单中获取用户填写的验证码         * 3. 进行比较！         * 4. 如果相同，向下运行，否则保存错误信息到request域，转发到login.jsp         */        String sessionCode = (String) request.getSession().getAttribute("session_vcode");        String paramCode = request.getParameter("verifyCode");                if(!paramCode.equalsIgnoreCase(sessionCode)) {            request.setAttribute("msg", "验证码错误！");            request.getRequestDispatcher("/login.jsp").forward(request, response);            return;        }        /*         * 1. 获取表单数据         */        // 处理中文问题        request.setCharacterEncoding("utf-8");        // 获取        String username = request.getParameter("username");        String password = request.getParameter("password");        /*         * 2. 校验用户名和密码是否正确         */        if("itcast".equalsIgnoreCase(username)) {//登录成功            /*             * 附加项：把用户名保存到cookie中，发送给客户端浏览器             * 当再次打开login.jsp时，login.jsp中会读取request中的cookie，把它显示到用户名文本框中             */            Cookie cookie = new Cookie("uname", username);//创建Cookie            cookie.setMaxAge(60*60*24);//设置cookie命长为1天            response.addCookie(cookie);//保存cookie                        /*             * 3. 如果成功             *   >  保存用户信息到session中             *   >  重定向到succ1.jsp             */            HttpSession session = request.getSession();//获取session            session.setAttribute("username", username);//向session域中保存用户名            response.sendRedirect("/Test/succ1.jsp");        } else {//登录失败            /*             * 4. 如果失败             *   > 保存错误信息到request域中             *   > 转发到login.jsp             */            request.setAttribute("msg", "用户名或密码错误!");            RequestDispatcher qr = request.getRequestDispatcher("/login.jsp");//得到转发器            qr.forward(request, response);//转发        }    }    }

<%@ 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="http://www.mamicode.com/">        <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="http://www.mamicode.com/styles.css">    --><script type="text/javascript">function _change() {    /*    1. 得到img元素    2. 修改其src    */    var imgEle = document.getElementById("img");    imgEle.src = "<%=basePath%>servlet/VerifyCodeServlet?a=" + new Date().getTime();}</script>  </head>    <body><%-- 本页面提供登录表单，还要显示错误信息 --%><h1>登录</h1> <%/*读取名为uname的Cookie!如果为空显示：""如果不为空显示：Cookie的值*/String uname = "";Cookie[] cs = request.getCookies();//获取请求中所有的cookieif(cs != null) {// 如果存在cookie    for(Cookie c : cs) {//循环遍历所有的cookie        if("uname".equals(c.getName())) {//查找名为uname的cookie            uname = c.getValue();//获取这个cookie的值，给uname这个变量        }    }}%><%    String message = "";    String msg = (String)request.getAttribute("msg");//获取request域中的名为msg的属性    if(msg != null) {        message = msg;    }%><font color="red"><b><%=message %> </b></font><form action="servlet/LoginServlet" method="post">            <%-- 把cookie中的用户名显示到用户名文本框中 --%>    用户名：<input type="text" name="username" value="http://www.mamicode.com/"/><br/>    密　码：<input type="password" name="password"/><br/>    验证码：<input type="text" name="verifyCode" size="3"/>            <img id="img" src="http://www.mamicode.com/servlet/VerifyCodeServlet"/>            <a href="javascript:_change()">换一张</a>            <br/>    <input type="submit" value="http://www.mamicode.com/登录"/></form>  </body></html>

<body><h1>succ1</h1><%String username = (String)session.getAttribute("username");if(username == null) {    /*    1. 向request域中保存错误信息，转发到login.jsp    */    request.setAttribute("msg", "您还没有登录!请先登录!");    request.getRequestDispatcher("/login.jsp").forward(request, response);    return;}%>欢迎欢迎，热烈欢迎，欢迎<%=username %>领导指导工作！  </body></html>

 <servlet>    <servlet-name>LoginServlet</servlet-name>    <servlet-class>com.lhy.web.servlet.LoginServlet</servlet-class>  </servlet>   <servlet-mapping>    <servlet-name>LoginServlet</servlet-name>    <url-pattern>/servlet/LoginServlet</url-pattern>  </servlet-mapping>    <servlet>    <servlet-name>VerifyCodeServlet</servlet-name>    <servlet-class>com.lhy.web.servlet.VerifyCodeServlet</servlet-class>  </servlet>   <servlet-mapping>    <servlet-name>VerifyCodeServlet</servlet-name>    <url-pattern>/servlet/VerifyCodeServlet</url-pattern>  </servlet-mapping>