JQuery Ajax后台无刷新验证用户名重复，前台验证两次密码一致，后台创建并验证验证码

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

这里写图片描述

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https://v3.bootcss.com/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～