主要用到知识：1.Servlet 2.request从客户端得到参数 3.response向客户端响应
4.字符编码解决乱码问题 5.jsp的使用 6.验证码
7.Cookie的使用 8.Session的使用 9.具体功能登录时自动补全用户名
10.jsp页面的用户信息校验，如果为null，则跳转登录。
////使用一个VerifyCodeServlet专门来生成验证码
login.jsp页面：
1 <%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> 2 <% 3 String path = request.getContextPath(); 4 String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; 5 %> 6 7 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 8 <html> 9 <head> 10 <base href="<%=basePath%>"> 11 12 <title>My JSP 'login.jsp' starting page</title> 13 14 <meta http-equiv="pragma" content="no-cache"> 15 <meta http-equiv="cache-control" content="no-cache"> 16 <meta http-equiv="expires" content="0"> 17 <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> 18 <meta http-equiv="description" content="This is my page"> 19 <!-- 20 <link rel="stylesheet" type="text/css" href="styles.css"> 21 --> 22 23 <script type="text/javascript"> 24 function _change(){ 25 //1.得到img元素 26 //2.修改其src为/XJS_Session/VerifyCodeServlet 27 var imgEle=document.getElementById("img"); 28 //有缓冲，加参数---时间 29 imgEle.src="/XJS_Session/VerifyCodeServlet?a="+new Date().getTime(); 30 } 31 </script> 32 </head> 33 34 <body> 35 <h1>登录</h1> 36 <% 37 String uname=""; 38 //读名为username的cookie 39 Cookie[] cookies=request.getCookies(); 40 if(cookies!=null){ 41 for(Cookie c:cookies){ 42 //如果为空显示："" 43 //如果不为显示：Cookie值 44 if("username".equals(c.getName())){ 45 uname=c.getValue(); 46 } 47 } 48 } 49 %> 50 51 <% 52 String message="";//一个空字符串 53 String msg=(String)request.getAttribute("msg");//获取错误信息 54 if(msg!=null){ 55 message=msg; 56 } 57 %> 58 <font color="red"><b><%=message %></b></font> 59 <form action="/XJS_Session/LoginServlet" method="post"> 60 用户名：<input type="text" name="username" value="<%=uname %>"><br> 61 密 码：<input type="password" name="password"><br> 62 验证码：<input type="text" name="verifyCode" size="7"> 63 <img id="img" src="/XJS_Session/VerifyCodeServlet"><br> 64 <a href="javascript:_change()">看不清，换一张</a> 65 <input type="submit" value="提交"> 66 </form> 67 </body> 68 </html>
LoginServlet.java:
1 public class LoginServlet extends HttpServlet { 2 3 public void doPost(HttpServletRequest request, HttpServletResponse response) 4 throws ServletException, IOException { 5 /* 6 * 校验验证码 7 * 1.从session中获取正确的验证码 8 * 2.从表单中获取用户输入的验证码 9 * 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 10 */ 11 HttpSession session1 = request.getSession(); 12 String vcode1 = (String) session1.getAttribute("session_vcode"); 13 String vcode2 = request.getParameter("verifyCode"); 14 System.out.println("1:"+vcode1+" 2:"+vcode2); 15 if(!vcode1.equalsIgnoreCase(vcode2)){//不相等----不区分大小写 16 request.setAttribute("msg", "验证码错误！"); 17 RequestDispatcher rd=request.getRequestDispatcher("/login.jsp"); 18 rd.forward(request, response); 19 return;//错误结束，就不向下执行 20 } 21 22 23 24 25 request.setCharacterEncoding("utf-8"); 26 String username = request.getParameter("username"); 27 String password = request.getParameter("password"); 28 System.out.println("username:"+username+", password:"+password); 29 if(username!="" && password!=""){ 30 if("xjs".equals(username) && "0309".equals(password)){ 31 //设置Cookie 32 response.setContentType("text/html;charset=utf-8"); 33 Cookie cookie=new Cookie("username",username); 34 cookie.setMaxAge(60*60); 35 response.addCookie(cookie);//把它显示到用户名文本框中 36 37 38 //登录成功 39 HttpSession session=session1; 40 session.setAttribute("username", username); 41 session.setAttribute("password", password); 42 //重定向到succ1.jsp 43 response.sendRedirect("/XJS_Session/succ1.jsp"); 44 } 45 else{ 46 System.out.println("username:"+username+", password:"+password); 47 //输入的用户名和密码不存在 48 request.setAttribute("msg", "用户名和密码不存在！！！"); 49 //用转发 50 RequestDispatcher rd=request.getRequestDispatcher("/login.jsp"); 51 rd.forward(request, response); 52 } 53 }else{ 54 request.setAttribute("msg", "用户名或密码不能为空！！！"); 55 //用转发---如果用重定向的话显示错误信息就不能使用request 56 RequestDispatcher rd=request.getRequestDispatcher("/login.jsp"); 57 rd.forward(request, response); 58 } 59 } 60 }
=============================验证码===========================
VerifyCode.java:
1 package com.xjs.commons; 2 3 import java.awt.BasicStroke; 4 import java.awt.Color; 5 import java.awt.Font; 6 import java.awt.Graphics2D; 7 import java.awt.image.BufferedImage; 8 import java.io.IOException; 9 import java.io.OutputStream; 10 import java.util.Random; 11 12 import javax.imageio.ImageIO; 13 14 public class VerifyCode { 15 private int w = 70; 16 private int h = 35; 17 private Random r = new Random(); 18 // {"宋体", "华文楷体", "黑体", "华文新魏", "华文隶书", "微软雅黑", "楷体_GB2312"} 19 private String[] fontNames = {"宋体", "华文楷体", "黑体", "微软雅黑", "楷体_GB2312"}; 20 // 可选字符 21 private String codes = "23456789abcdefghjkmnopqrstuvwxyzABCDEFGHJKMNPQRSTUVWXYZ"; 22 // 背景色 23 private Color bgColor = new Color(255, 255, 255); 24 // 验证码上的文本 25 private String text ; 26 27 // 生成随机的颜色 28 private Color randomColor () { 29 int red = r.nextInt(150); 30 int green = r.nextInt(150); 31 int blue = r.nextInt(150); 32 return new Color(red, green, blue); 33 } 34 35 // 生成随机的字体 36 private Font randomFont () { 37 int index = r.nextInt(fontNames.length); 38 String fontName = fontNames[index];//生成随机的字体名称 39 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) 40 int size = r.nextInt(5) + 24; //生成随机字号, 24 ~ 28 41 return new Font(fontName, style, size); 42 } 43 44 // 画干扰线 45 private void drawLine (BufferedImage image) { 46 int num = 3;//一共画3条 47 Graphics2D g2 = (Graphics2D)image.getGraphics(); 48 for(int i = 0; i < num; i++) {//生成两个点的坐标，即4个值 49 int x1 = r.nextInt(w); 50 int y1 = r.nextInt(h); 51 int x2 = r.nextInt(w); 52 int y2 = r.nextInt(h); 53 g2.setStroke(new BasicStroke(1.5F)); 54 g2.setColor(Color.BLUE); //干扰线是蓝色 55 g2.drawLine(x1, y1, x2, y2);//画线 56 } 57 } 58 59 // 随机生成一个字符 60 private char randomChar () { 61 int index = r.nextInt(codes.length()); 62 return codes.charAt(index); 63 } 64 65 // 创建BufferedImage 66 private BufferedImage createImage () { 67 BufferedImage image = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB); 68 Graphics2D g2 = (Graphics2D)image.getGraphics(); 69 g2.setColor(this.bgColor); 70 g2.fillRect(0, 0, w, h); 71 return image; 72 } 73 74 // 调用这个方法得到验证码 75 public BufferedImage getImage () { 76 BufferedImage image = createImage();//创建图片缓冲区 77 Graphics2D g2 = (Graphics2D)image.getGraphics();//得到绘制环境 78 StringBuilder sb = new StringBuilder();//用来装载生成的验证码文本 79 // 向图片中画4个字符 80 for(int i = 0; i < 4; i++) {//循环四次，每次生成一个字符 81 String s = randomChar() + "";//随机生成一个字母 82 sb.append(s); //把字母添加到sb中 83 float x = i * 1.0F * w / 4; //设置当前字符的x轴坐标 84 g2.setFont(randomFont()); //设置随机字体 85 g2.setColor(randomColor()); //设置随机颜色 86 g2.drawString(s, x, h-5); //画图 87 } 88 this.text = sb.toString(); //把生成的字符串赋给了this.text 89 drawLine(image); //添加干扰线 90 return image; 91 } 92 93 // 返回验证码图片上的文本 94 public String getText () { 95 return text; 96 } 97 98 // 保存图片到指定的输出流 99 public static void output (BufferedImage image, OutputStream out) 100 throws IOException { 101 ImageIO.write(image, "JPEG", out); 102 } 103 }
VerifyCodeServlet.java:
1 import java.awt.image.BufferedImage; 2 import java.io.IOException; 3 import java.io.PrintWriter; 4 5 import javax.servlet.ServletException; 6 import javax.servlet.http.HttpServlet; 7 import javax.servlet.http.HttpServletRequest; 8 import javax.servlet.http.HttpServletResponse; 9 10 import com.xjs.commons.VerifyCode; 11 12 public class VerifyCodeServlet extends HttpServlet { 13 14 public void doGet(HttpServletRequest request, HttpServletResponse response) 15 throws ServletException, IOException { 16 /** 17 * 1.生成图片 18 * 2.保存图片上的文本到session中 19 * 3.把图片响应到客户端 20 */ 21 VerifyCode vc=new VerifyCode(); 22 BufferedImage bi=vc.getImage(); 23 request.getSession().setAttribute("session_vcode", vc.getText()); 24 //参数输出流，ServletOutputStream getOutputStream();返回输入流---跟getWriter()方法不能同时使用，跟JavaSE中的输出流类似 25 VerifyCode.output(bi, response.getOutputStream()); 26 } 27 }
////////////////////
succ1.jsp和succ2.jsp：
1 <body> 2 <% 3 4 if(session.getAttribute("username")==null&&session.getAttribute("password")==null){ 5 //重定向到login.jsp 6 response.sendRedirect("/XJS_Session/login.jsp"); 7 return;//别的就不执行了 8 } 9 %> 10 <% 11 String username=(String)session.getAttribute("username"); 12 String password=(String)session.getAttribute("password"); 13 out.print("用户名："+username); 14 out.print("密码："+password); 15 16 %> 17 </body>