写在前面
写web 的人，我想最先要解决的就是注册登录的界面了，一个小小的界面却包含着各种基本的知识，让我这个新手摸了一天。
效果图
知识
1.bootstrap渲染表单
2.JQuery ajax验证用户名
3.两次密码输入要一致
4.后台密码验证
5.点击图片刷新
代码
前台
test.html
<!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><title>Title</title><link rel="stylesheet" href="css/bootstrap.min.css"><script src="js/jquery-3.3.1.js"></script><script src="js/bootstrap.min.js"></script></head><body><div class="container"><div id="form-box" class="row col-md-6"><div class="row"><form class="form-horizontal" action="/RegisterValidateServlet" method="post"><fieldset><legend>用户注册</legend><div class="form-group"><label for="username" class="control-label col-md-2">用户名:</label><div class="col-md-6 has-feedback" id="username-box"><input type="text" class="form-control" id="username" name="username" required><span id="user-exists" class="glyphicon form-control-feedback"></span></div><p id="username-help" class="help-block"></p></div><div class="form-group"><label for="password" class="control-label col-md-2">密码:</label><div class="col-md-6 "><input type="password" class="form-control" id="password" name="password" required></div></div><div class="form-group"><label for="password2" class="control-label col-md-2">确认密码:</label><div class="col-md-6 has-feedback" id="password2-box"><input type="password" class="form-control" id="password2" name="password2" required><span id="miss-matching" class="glyphicon form-control-feedback"></span></div><p id="password2-help" class="help-block"></p></div><div class="form-group"><label for="identify" class="col-md-2 control-label">验证码:</label><div class="col-md-2"><input type="text" class="form-control" id="identify" name="identify" required></div><img id="identify-code"></div><div class="form-group"><div class="col-md-6 col-md-push-2"><input type="submit" class="btn btn-info" value="提交"></div></div></fieldset></form></div></div></div><script>$(function () {/*这个可以防止浏览器后退时候图片不刷新*/$("#identify-code").prop("src", "/IdentifyingCodeServlet?" + new Date().getTime());let $form = $("form");/*点击框自动清空内容*/$form.on("click", ":input[type!=submit]", function () {$(this).prop("value", "");});/*添加勾这个图标*/function addOK(box, span) {span.removeClass("glyphicon-remove");box.removeClass("has-error");span.addClass("glyphicon-ok");box.addClass("has-success");}/*添加×这个图标*/function addRemove(box, span) {span.removeClass("glyphicon-ok");box.removeClass("has-success");span.addClass("glyphicon-remove");box.addClass("has-error");}/*两次密码验证*/$("#password2,#password").blur(function () {let password = $("#password").val();let password2 = $("#password2").val();let $missmatchingSpan = $("#miss-matching");let $password2Box = $("#password2-box");let $password2Help = $("#password2-help");if (password.trim() === "" || password2.trim() === "" || password2 !== password) {addRemove($password2Box, $missmatchingSpan);$password2Help.html("两次密码不一致");} else {addOK($password2Box, $missmatchingSpan);$password2Help.html("");}});/*ajax验证后台用户名是否存在*/$("#username").blur(function () {let username = $("#username").val().trim();if (username !== "") {$.ajax({url: "RegisterValidateServlet",type: "post",data: {username: username},dataType: "text",success: function (data) {let $usernameBox = $("#username-box");let $userExistsSpan = $("#user-exists");let $usernameHelp = $("#username-help");if (data === "exists") {addRemove($usernameBox, $userExistsSpan);$usernameHelp.html("用户名已存在");} else {addOK($usernameBox, $userExistsSpan);$usernameHelp.html("用户名可以用");}},error: function (error) {alert(error);}})}});/*点击生成新的验证码*/$("#identify-code").click(function () {$(this).prop("src", "/IdentifyingCodeServlet?" + new Date().getTime());});})</script></body></html>
由于这些代码都是自己想到的，肯定有更好的写法，比如用JQuery框架等，由于我是想从事后端的，就不在这上纠结了。图标是由官网来的，上面有教学，可以看下这里是地址/components/，起步中有响应的bootstrap 渲染教程，也可以学习一下哈。ajax是很好的异步技术，是肯定要懂的。加上时间戳能够让浏览器不用缓存，发送新的请求。
后台
验证码Servlet
package web.controller;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;import java.awt.*;import java.awt.image.BufferedImage;import java.io.IOException;import java.util.Random;@WebServlet(name = "IdentifyingCodeServlet")public class IdentifyingCodeServlet extends HttpServlet {protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {}protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {BufferedImage bfi = new BufferedImage(80, 25, BufferedImage.TYPE_INT_RGB);Graphics2D graphics = (Graphics2D) bfi.getGraphics();// 设置背景色graphics.setColor(Color.WHITE);graphics.fillRect(0, 0, 80, 25);// 设置边框graphics.setColor(Color.BLACK);graphics.drawRect(0, 0, 80 - 1, 25 - 1);String str = drawRandomNum(graphics);System.out.println(str);HttpSession session = request.getSession();session.setAttribute("identifyCode", str);drawPoint(bfi);drawInfluencedLine(graphics);response.setHeader("Expires", "-1");response.setHeader("Cache-Control", "no-cache");response.setHeader("Cache-Control", "no-store");response.setHeader("Pragma", "no-cache");response.setHeader("content-type", "image/jpeg");ImageIO.write(bfi, "jpg", response.getOutputStream());}// 画上点private void drawPoint(BufferedImage bfi) {int area = (int) (0.02 * 80 * 25);for (int i = 0; i < area; ++i) {int x = (int) (Math.random() * 80);int y = (int) (Math.random() * 25);bfi.setRGB(x, y, (int) (Math.random() * 255));}}private void drawInfluencedLine(Graphics2D g) {//设置验证码中的干扰线for (int i = 0; i < 3; i++) {Random random = new Random();//随机获取干扰线的起点和终点int xstart = random.nextInt(80);int ystart = random.nextInt(25);int xend = random.nextInt(80);int yend = random.nextInt(25);g.setColor(new Color(random.nextInt(255), random.nextInt(255), random.nextInt(255)));g.drawLine(xstart, ystart, xend, yend);}}// 生成随机数旋转后写入private String drawRandomNum(Graphics2D g) {char[] chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890".toCharArray();Random random = new Random();int index;StringBuilder builder = new StringBuilder();for (int i = 0; i < 4; i++) {// 从字符数组中获得随机字符index = random.nextInt(chars.length);String value = chars[index] + "";// 设置随机字符的颜色g.setColor(new Color(random.nextInt(255), random.nextInt(255), random.nextInt(255)));// 字体格式Font font = new Font(null, Font.BOLD, 20);g.setFont(font);//生成-30~30之间的数字int dgree = random.nextInt(60) - 30;//旋转g.rotate(dgree * Math.PI / 180, i * 20 + 2, 23);// 写入字符g.drawString(value, i * 20 + 2, 20);// 把画笔再转回去,免得影响下次的弧度g.rotate(-dgree * Math.PI / 180, i * 20 + 2, 23);builder.append(value);}return builder.toString();}}
验证码里面比较重要的就是，缓存的设置了，验证码这种及时性的需要禁止浏览器缓存，保证它的及时刷新。再加上前台的时间戳，就能够保证了。
简单验证Servlet
package web.controller;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 java.io.IOException;import java.util.Enumeration;@WebServlet(name = "web.controller.RegisterValidateServlet")public class RegisterValidateServlet extends HttpServlet {protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doGet(request, response);}protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {request.setCharacterEncoding("UTF-8");response.setCharacterEncoding("UTF-8");response.setContentType("text/html;charset=UTF-8");String username = "123";String user = request.getParameter("username");String identifyCode = request.getParameter("identify");if (identifyCode != null) {String identifySession = (String) request.getSession().getAttribute("identifyCode");if (identifyCode.equals(identifySession)) {request.setAttribute("message", "注册成功");request.getRequestDispatcher("/message.jsp").forward(request, response);}}if (user.equals(username)) {response.getWriter().write("exists");}}}
待改进之处
如果有坏人自己写个html，把前台脚本都删掉，这个时候就需要后台的验证前台的两次密码相同处理不好，第一次输入密码的时候不应该有错误框。前台的复杂验证未实现，可以用正则表达式。总结
本次学习，一在练习bootstrap 和简单的JQuery，ajax，虽然以后从事后端，java代码熟悉。但是这些前台的东西，还是要了解的，不然你看着那个很丑的表格不难受吗？对吧。现在的知识很多，但是能慢慢学习的人却很少，所以 从什么时候开始学都不晚，我现在马上大四了，还在servlet+jsp期间，框架还没学，但是我相信只有把基础打牢，才能走得更远。共勉～
