目录

1、 AJAX

1.1 概述

AJAX (Asynchronous JavaScript And XML)：异步的 JavaScript 和 XML。

1.1.1 作用

  1. 与服务器进行数据交换

    • 使用JSP

      • 浏览器发送请求Servlet
      • Servlet调用完业务逻辑层之后，将数据存储到Request域对象中
      • 转发到对应JSP进行展示（将JSP作为视图）

    • 使用AJAX：AJAX可以给服务器发送请求，并获取服务器响应的数据

      使用AJAX+HTML替换JSP

      • 浏览器发送请求Servlet
      • Servlet调用完业务逻辑层后将数据通过AJAX直接响应回给浏览器页面
      • 页面使用HTML来进行数据展示

  2. 异步交互

    • 可以在不重新加载整个页面的情况下，与服务器交换数据并更新部分网页的技术，如：搜索联想、用户名是否可用校验，点击关注，点击收藏，等等…

1.1.2 同步和异步

  • 同步发送请求的过程

    • 客户端访问服务器
    • 服务器处理客户端请求
    • 服务器返回处理结果到客户端
    • 客户端进行其他请求

  • 异步发送请求的过程：不用等待服务器端

    • 客户端访问服务器
    • 服务器处理客户端请求（期间客户端可进行其他操作）
    • 服务器返回处理结果到客户端
    • 客户端进行其他请求

1.2 快速入门

1.2.1 服务端实现

  • 编写Servlet

    package priv.dandelion.controller.servlet;

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;

@WebServlet("/ajaxDemo")
public class AjaxDemo extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 响应数据
        resp.getWriter().write("hello ajax~");
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req, resp);
    }
}

1.2.2 客户端实现

  • 步骤说明

    1. 创建xhttp核心对象
    2. 建立连接
    3. 发送请求
    4. 获取响应

  • 完整代码

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>AJAX-demo1</title>
</head>
<body>

<script>

    // 创建核心对象
    var xhttp;
    if (window.XMLHttpRequest) {
        xhttp = new XMLHttpRequest();
    } else {
        // code for IE6, IE5
        xhttp = new ActiveXObject("Microsoft.XMLHTTP");
    }

    // 建立连接（包含第三个参数，为true是异步，默认异步，此处省略）
    xhttp.open("GET", "http://localhost:8080/ajax-demo/ajaxDemo");

    // 发送请求
    xhttp.send();

    // 获取响应，监听到onreadystatechange就绪状态事件，事件发生变化时执行函数
    xhttp.onreadystatechange = function() {
        // this.readyState == 4 表示请求发送结束且响应就绪，this.status == 200表示成功收到响应
        if (this.readyState == 4 && this.status == 200) {
            // 通过 this.responseText 可以获取到服务端响应的数据
            alert(this.responseText);
        }
    };

</script>

</body>
</html>

1.3 案例

1.3.1 需求

  • 用户注册功能

  • 在用户名输入框失去焦点时，校验该用户名是否存在，并在页面中给出提示

1.3.2 分析

  • 前端

    1. 给用户名输入框绑定光标失去焦点事件onblur
    2. 发送ajax请求，携带username参数

  • 后端

    1. 接收用户名
    2. 调用service查询User
    3. 返回标记

1.3.2 后端实现

  • 环境准备

    • 依赖

      <?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>priv.dandelion</groupId>
    <artifactId>ajax-demo</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>war</packaging>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>

    <dependencies>
        <!-- junit单元测试依赖 -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.11</version>
            <scope>test</scope>
        </dependency>
        <!--mybatis 依赖-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.5</version>
        </dependency>
        <!--mysql 驱动-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.46</version>
        </dependency>
        <!-- 添加slf4j日志api -->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>1.7.20</version>
        </dependency>
        <!-- 添加logback-classic依赖 -->
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>1.2.3</version>
        </dependency>
        <!-- 添加logback-core依赖 -->
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-core</artifactId>
            <version>1.2.3</version>
        </dependency>
        <!-- servlet依赖 -->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>3.1.0</version>
            <scope>provided</scope>
        </dependency>
        <!-- JSP依赖 -->
        <dependency>
            <groupId>javax.servlet.jsp</groupId>
            <artifactId>jsp-api</artifactId>
            <version>2.2</version>
            <scope>provided</scope>
        </dependency>
        <!-- JSTL依赖 -->
        <dependency>
            <groupId>jstl</groupId>
            <artifactId>jstl</artifactId>
            <version>1.2</version>
        </dependency>
        <!-- JSTL标准标签库依赖 -->
        <dependency>
            <groupId>taglibs</groupId>
            <artifactId>standard</artifactId>
            <version>1.1.2</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <!-- tomcat插件 -->
                <groupId>org.apache.tomcat.maven</groupId>
                <artifactId>tomcat7-maven-plugin</artifactId>
                <version>2.2</version>
            </plugin>
        </plugins>
    </build>

</project>

    • SQL

      -- 删除tb_user表
drop table if exists tb_user;
-- 创建用户表
CREATE TABLE tb_user(
	id int primary key auto_increment,
	username varchar(20) unique,
	password varchar(32)
);

-- 添加数据
INSERT INTO tb_user(username,password) values('zhangsan','123'),('lisi','234');

SELECT * FROM tb_user;

    • 静态页面

      • CSS

        * {
    margin: 0;
    padding: 0;
    list-style-type: none;
}
.reg-content{
    padding: 30px;
    margin: 3px;
}
a, img {
    border: 0;
}

body {
    background-image: url("../imgs/reg_bg_min.jpg") ;
    text-align: center;
}

table {
    border-collapse: collapse;
    border-spacing: 0;
}

td, th {
    padding: 0;
    height: 90px;

}
.inputs{
    vertical-align: top;
}

.clear {
    clear: both;
}

.clear:before, .clear:after {
    content: "";
    display: table;
}

.clear:after {
    clear: both;
}

.form-div {
    background-color: rgba(255, 255, 255, 0.27);
    border-radius: 10px;
    border: 1px solid #aaa;
    width: 424px;
    margin-top: 150px;
    margin-left:1050px;
    padding: 30px 0 20px 0px;
    font-size: 16px;
    box-shadow: inset 0px 0px 10px rgba(255, 255, 255, 0.5), 0px 0px 15px rgba(75, 75, 75, 0.3);
    text-align: left;
}

.form-div input[type="text"], .form-div input[type="password"], .form-div input[type="email"] {
    width: 268px;
    margin: 10px;
    line-height: 20px;
    font-size: 16px;
}

.form-div input[type="checkbox"] {
    margin: 20px 0 20px 10px;
}

.form-div input[type="button"], .form-div input[type="submit"] {
    margin: 10px 20px 0 0;
}

.form-div table {
    margin: 0 auto;
    text-align: right;
    color: rgba(64, 64, 64, 1.00);
}

.form-div table img {
    vertical-align: middle;
    margin: 0 0 5px 0;
}

.footer {
    color: rgba(64, 64, 64, 1.00);
    font-size: 12px;
    margin-top: 30px;
}

.form-div .buttons {
    float: right;
}

input[type="text"], input[type="password"], input[type="email"] {
    border-radius: 8px;
    box-shadow: inset 0 2px 5px #eee;
    padding: 10px;
    border: 1px solid #D4D4D4;
    color: #333333;
    margin-top: 5px;
}

input[type="text"]:focus, input[type="password"]:focus, input[type="email"]:focus {
    border: 1px solid #50afeb;
    outline: none;
}

input[type="button"], input[type="submit"] {
    padding: 7px 15px;
    background-color: #3c6db0;
    text-align: center;
    border-radius: 5px;
    overflow: hidden;
    min-width: 80px;
    border: none;
    color: #FFF;
    box-shadow: 1px 1px 1px rgba(75, 75, 75, 0.3);
}

input[type="button"]:hover, input[type="submit"]:hover {
    background-color: #5a88c8;
}

input[type="button"]:active, input[type="submit"]:active {
    background-color: #5a88c8;
}
.err_msg{
    color: red;
    padding-right: 170px;
}
#password_err,#tel_err{
    padding-right: 195px;
}

#reg_btn{
    margin-right:50px; width: 285px; height: 45px; margin-top:20px;
}

#checkCode{
    width: 100px;
}

#changeImg{
    color: aqua;
}

      • HTML

        <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>欢迎注册</title>
    <link href="css/register.css" rel="stylesheet">
</head>
<body>

<div class="form-div">
    <div class="reg-content">
        <h1>欢迎注册</h1>
        <span>已有帐号？</span> <a href="login.html">登录</a>
    </div>
    <form id="reg-form" action="#" method="get">

        <table>

            <tr>
                <td>用户名</td>
                <td class="inputs">
                    <input name="username" type="text" id="username">
                    <br>
                    <span id="username_err" class="err_msg" style="display: none">用户名不太受欢迎</span>
                </td>

            </tr>

            <tr>
                <td>密码</td>
                <td class="inputs">
                    <input name="password" type="password" id="password">
                    <br>
                    <span id="password_err" class="err_msg" style="display: none">密码格式有误</span>
                </td>
            </tr>


            <tr>
                <td>验证码</td>
                <td class="inputs">
                    <input name="checkCode" type="text" id="checkCode">
                    <img src="imgs/a.jpg">
                    <a href="#" id="changeImg">看不清？</a>
                </td>
            </tr>

        </table>

        <div class="buttons">
            <input value="注 册" type="submit" id="reg_btn">
        </div>
        <br class="clear">
    </form>

</div>
</body>
</html>

    • 数据库

      • 核心配置文件

        <?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <!--起别名-->
    <typeAliases>
        <package name="priv.dandelion.entity"/>
    </typeAliases>

    <environments default="development">
        <environment id="development">
            <!-- 采用JDBC的事务管理方式 -->
            <transactionManager type="JDBC"/>
            <!-- 数据库连接信息 -->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <!-- value的值一定不能换行，一定！一定！不能换行 -->
                <property name="url" value="jdbc:mysql:///db1?useSSL=false&amp;useUnicode=true&amp;characterEncoding=utf-8&amp;useServerPrepStmts=true"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
    <!-- 扫描mapper，加载SQL映射文件 -->
    <mappers>
        <package name="priv.dandelion.dao"/>
    </mappers>
</configuration>

      • Mapper映射文件

        <?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="priv.dandelion.dao.UserMapper">
</mapper>

    • 工具类

      • 获取SqlSessionFactory

        package priv.dandelion.utils;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.IOException;
import java.io.InputStream;

public class SqlSessionFactoryUtils {

    // 提升作用域，用于再方法内进行返回
    private static SqlSessionFactory sqlSessionFactory;

    // 静态代码块会随着类的加载自动执行且只执行一次
    static {
        String resource = "mybatis-config.xml";
        InputStream inputStream = null;
        try {
            inputStream = Resources.getResourceAsStream(resource);
        } catch (IOException e) {
            e.printStackTrace();
        }
        sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    }

    public static SqlSessionFactory getSqlSessionFactory() {
        return sqlSessionFactory;
    }

}

      • 重编码ISO-8859-1为UTF-8

        package priv.dandelion.utils;

import java.nio.charset.StandardCharsets;

public class ReEncoding {

    public static String reEncodingToUtf8(String str) {
        // 使用ISO-8859-1编码将乱码字符编回二进制码，得到其字节数组
        byte[] bytes = str.getBytes(StandardCharsets.ISO_8859_1);
        // 将字节数组使用UTF-8重新编码
        return new String(bytes, StandardCharsets.UTF_8);
    }
}

      • 验证码生成

        package priv.dandelion.utils;

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Arrays;
import java.util.Random;

/**
 * 生成验证码工具类
 */
public class CheckCodeUtil {

    public static final String VERIFY_CODES = "123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    private static Random random = new Random();



    /**
     * 输出随机验证码图片流,并返回验证码值（一般传入输出流，响应response页面端，Web项目用的较多）
     *
     * @param width 图片宽度
     * @param height 图片高度
     * @param os 输出流
     * @param verifySize 验证码长度
     * @return String
     * @throws IOException
     */
    public static String outputVerifyImage(int width, int height, OutputStream os, int verifySize) throws IOException {
        String verifyCode = generateVerifyCode(verifySize);
        outputImage(width, height, os, verifyCode);
        return verifyCode;
    }

    /**
     * 使用系统默认字符源生成验证码
     *
     * @param verifySize 验证码长度
     * @return
     */
    public static String generateVerifyCode(int verifySize) {
        return generateVerifyCode(verifySize, VERIFY_CODES);
    }

    /**
     * 使用指定源生成验证码
     *
     * @param verifySize 验证码长度
     * @param sources    验证码字符源
     * @return
     */
    public static String generateVerifyCode(int verifySize, String sources) {
        // 未设定展示源的字码，赋默认值大写字母+数字
        if (sources == null || sources.length() == 0) {
            sources = VERIFY_CODES;
        }
        int codesLen = sources.length();
        Random rand = new Random(System.currentTimeMillis());
        StringBuilder verifyCode = new StringBuilder(verifySize);
        for (int i = 0; i < verifySize; i++) {
            verifyCode.append(sources.charAt(rand.nextInt(codesLen - 1)));
        }
        return verifyCode.toString();
    }

    /**
     * 生成随机验证码文件,并返回验证码值 (生成图片形式，用的较少)
     *
     * @param w
     * @param h
     * @param outputFile
     * @param verifySize
     * @return
     * @throws IOException
     */
    public static String outputVerifyImage(int w, int h, File outputFile, int verifySize) throws IOException {
        String verifyCode = generateVerifyCode(verifySize);
        outputImage(w, h, outputFile, verifyCode);
        return verifyCode;
    }



    /**
     * 生成指定验证码图像文件
     *
     * @param w
     * @param h
     * @param outputFile
     * @param code
     * @throws IOException
     */
    public static void outputImage(int w, int h, File outputFile, String code) throws IOException {
        if (outputFile == null) {
            return;
        }
        File dir = outputFile.getParentFile();
        //文件不存在
        if (!dir.exists()) {
            //创建
            dir.mkdirs();
        }
        try {
            outputFile.createNewFile();
            FileOutputStream fos = new FileOutputStream(outputFile);
            outputImage(w, h, fos, code);
            fos.close();
        } catch (IOException e) {
            throw e;
        }
    }

    /**
     * 输出指定验证码图片流
     *
     * @param w
     * @param h
     * @param os
     * @param code
     * @throws IOException
     */
    public static void outputImage(int w, int h, OutputStream os, String code) throws IOException {
        int verifySize = code.length();
        BufferedImage image = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
        Random rand = new Random();
        Graphics2D g2 = image.createGraphics();
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

        // 创建颜色集合，使用java.awt包下的类
        Color[] colors = new Color[5];
        Color[] colorSpaces = new Color[]{Color.WHITE, Color.CYAN,
                Color.GRAY, Color.LIGHT_GRAY, Color.MAGENTA, Color.ORANGE,
                Color.PINK, Color.YELLOW};
        float[] fractions = new float[colors.length];
        for (int i = 0; i < colors.length; i++) {
            colors[i] = colorSpaces[rand.nextInt(colorSpaces.length)];
            fractions[i] = rand.nextFloat();
        }
        Arrays.sort(fractions);
        // 设置边框色
        g2.setColor(Color.GRAY);
        g2.fillRect(0, 0, w, h);

        Color c = getRandColor(200, 250);
        // 设置背景色
        g2.setColor(c);
        g2.fillRect(0, 2, w, h - 4);

        // 绘制干扰线
        Random random = new Random();
        // 设置线条的颜色
        g2.setColor(getRandColor(160, 200));
        for (int i = 0; i < 20; i++) {
            int x = random.nextInt(w - 1);
            int y = random.nextInt(h - 1);
            int xl = random.nextInt(6) + 1;
            int yl = random.nextInt(12) + 1;
            g2.drawLine(x, y, x + xl + 40, y + yl + 20);
        }

        // 添加噪点
        // 噪声率
        float yawpRate = 0.05f;
        int area = (int) (yawpRate * w * h);
        for (int i = 0; i < area; i++) {
            int x = random.nextInt(w);
            int y = random.nextInt(h);
            // 获取随机颜色
            int rgb = getRandomIntColor();
            image.setRGB(x, y, rgb);
        }
        // 添加图片扭曲
        shear(g2, w, h, c);

        g2.setColor(getRandColor(100, 160));
        int fontSize = h - 4;
        Font font = new Font("Algerian", Font.ITALIC, fontSize);
        g2.setFont(font);
        char[] chars = code.toCharArray();
        for (int i = 0; i < verifySize; i++) {
            AffineTransform affine = new AffineTransform();
            affine.setToRotation(Math.PI / 4 * rand.nextDouble() * (rand.nextBoolean() ? 1 : -1), (w / verifySize) * i + fontSize / 2, h / 2);
            g2.setTransform(affine);
            g2.drawChars(chars, i, 1, ((w - 10) / verifySize) * i + 5, h / 2 + fontSize / 2 - 10);
        }

        g2.dispose();
        ImageIO.write(image, "jpg", os);
    }

    /**
     * 随机颜色
     *
     * @param fc
     * @param bc
     * @return
     */
    private static Color getRandColor(int fc, int bc) {
        if (fc > 255) {
            fc = 255;
        }
        if (bc > 255) {
            bc = 255;
        }
        int r = fc + random.nextInt(bc - fc);
        int g = fc + random.nextInt(bc - fc);
        int b = fc + random.nextInt(bc - fc);
        return new Color(r, g, b);
    }

    private static int getRandomIntColor() {
        int[] rgb = getRandomRgb();
        int color = 0;
        for (int c : rgb) {
            color = color << 8;
            color = color | c;
        }
        return color;
    }

    private static int[] getRandomRgb() {
        int[] rgb = new int[3];
        for (int i = 0; i < 3; i++) {
            rgb[i] = random.nextInt(255);
        }
        return rgb;
    }

    private static void shear(Graphics g, int w1, int h1, Color color) {
        shearX(g, w1, h1, color);
        shearY(g, w1, h1, color);
    }

    private static void shearX(Graphics g, int w1, int h1, Color color) {

        int period = random.nextInt(2);

        boolean borderGap = true;
        int frames = 1;
        int phase = random.nextInt(2);

        for (int i = 0; i < h1; i++) {
            double d = (double) (period >> 1)
                    * Math.sin((double) i / (double) period
                    + (6.2831853071795862D * (double) phase)
                    / (double) frames);
            g.copyArea(0, i, w1, 1, (int) d, 0);
            if (borderGap) {
                g.setColor(color);
                g.drawLine((int) d, i, 0, i);
                g.drawLine((int) d + w1, i, w1, i);
            }
        }

    }

    private static void shearY(Graphics g, int w1, int h1, Color color) {

        int period = random.nextInt(40) + 10; // 50;

        boolean borderGap = true;
        int frames = 20;
        int phase = 7;
        for (int i = 0; i < w1; i++) {
            double d = (double) (period >> 1)
                    * Math.sin((double) i / (double) period
                    + (6.2831853071795862D * (double) phase)
                    / (double) frames);
            g.copyArea(i, 0, 1, h1, 0, (int) d);
            if (borderGap) {
                g.setColor(color);
                g.drawLine(i, (int) d, i, 0);
                g.drawLine(i, (int) d + h1, i, h1);
            }

        }

    }
}

    • 实体类

      • User

        package priv.dandelion.entity;

public class User {
    private Integer id;
    private String username;
    private String password;

    public User(Integer id, String username, String password) {
        this.id = id;
        this.username = username;
        this.password = password;
    }

    public User() {
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}

  • 编码

    • Dao

      • UserMapper

        package priv.dandelion.dao;

import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;
import priv.dandelion.entity.User;

import java.util.List;

public interface UserMapper {
    @Select("select * from tb_user where username = #{name}")
    public User selectByName(@Param("name") String name);
}

    • Service

      • UserService

        package priv.dandelion.service;

import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import priv.dandelion.dao.UserMapper;
import priv.dandelion.entity.User;
import priv.dandelion.utils.SqlSessionFactoryUtils;

public class UserService {

    private SqlSessionFactory factory = SqlSessionFactoryUtils.getSqlSessionFactory();

    public boolean selectUsername(String username) {
        // 获取SqlSession
        SqlSession sqlSession = factory.openSession(true);
        // 获取UserMapper
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        // 调用dao
        User user = mapper.selectByName(username);
        // 释放资源
        sqlSession.close();
        return user != null;
    }

}

    • Controller - Servlet

      • 用户名是否存在

        package priv.dandelion.controller.servlet;

import priv.dandelion.service.UserService;
import priv.dandelion.utils.ReEncoding;

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;

@WebServlet("/selectUsername")
public class SelectUsernameServlet extends HttpServlet {

    UserService service = new UserService();

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 接收用户名
        String username = req.getParameter("username");
        // 调用Service查询User
        boolean flag = service.selectUsername(username);
        // 响应标记
        resp.getWriter().write("" + flag);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req, resp);
    }
}

      • 展示验证码

        package priv.dandelion.controller.servlet;

import priv.dandelion.utils.CheckCodeUtil;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
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.io.IOException;

/**
 * 验证码展示，并存储到Session
 */
@WebServlet("/checkCode")
public class CheckCodeServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 存储验证码图片到本地
        // OutputStream fos = new FileOutputStream("d://check-code.jpg");

        // 使用Response字节输出流获取验证码
        ServletOutputStream outputStream = resp.getOutputStream();
        String checkCode = CheckCodeUtil.outputVerifyImage(100, 50, outputStream, 4);

        // 将验证码存储到Session中
        HttpSession session = req.getSession();
        session.setAttribute("checkCodeGenerate", checkCode);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req, resp);
    }
}

1.3.3 前端实现

  • 步骤说明

    1. 给用户名输入框绑定光标失去事件onblur
    2. 发送Ajax请求，携带username参数
    3. 处理响应

  • JS代码

    • 检验用户名是否存在

      // 给用户名输入框绑定发失去焦点事件
document.getElementById("username").onblur = function () {
    // 发送ajax请求
    // 获取用户名的值
    var username = this.value;

    // 创建核心对象
    var xhttp;
    if (window.XMLHttpRequest) {
        xhttp = new XMLHttpRequest();
    } else {
        // code for IE6, IE5
        xhttp = new ActiveXObject("Microsoft.XMLHTTP");
    }
    // 建立连接
    xhttp.open("GET", "http://localhost:8080/ajax-demo/selectUsername?username="+username);
    // 发送请求
    xhttp.send();

    // 获取响应
    xhttp.onreadystatechange = function() {
        if (this.readyState == 4 && this.status == 200) {
            //判断
            if(this.responseText == "true"){
                //用户名存在，显示提示信息，清除style中的display的none
                document.getElementById("username_err").style.display = '';
            }else {
                //用户名不存在，清除提示信息，设置style中的display为none，不显示
                document.getElementById("username_err").style.display = 'none';
            }
        }
    };
}

    • 验证码刷新

      // 验证码刷新
document.getElementById("changeImg").onclick = function () {
    // 图片路径已经被缓存，需要在后面加参数进行刷新，为保证多次刷新，可以以时间毫秒数作为参数
    document.getElementById("checkCodeImg").src = "/filter_demo/checkCode?"+new Date().getMilliseconds();
}

2、 Axios异步框架

Axios 对原生的AJAX进行封装，简化书写。

Axios官网是：https://www.axios-http.cn

2.1 基本使用

  • 引入Axios 的JavaScript文件

    <script src="js/axios-0.18.0.js"></script>

  • 发送请求并获取响应

    axios({})为发送请求部分，.then(function (resp){});为回调函数，使用resp.data可以获取到返回的结果

    • get

      axios({
    method:"get",
    url:"http://localhost:8080/ajax-demo1/aJAXDemo1?username=zhangsan"
}).then(function (resp){
    alert(resp.data);
})

    • post

      axios({
    method:"post",
    url:"http://localhost:8080/ajax-demo1/aJAXDemo1",
    data:"username=zhangsan"
}).then(function (resp){
    alert(resp.data);
});

2.2 快速入门

2.2.1 后端实现

package priv.dandelion.controller.servlet;

import priv.dandelion.utils.ReEncoding;

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;

@WebServlet("/axiosDemo")
public class AxiosDemo extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 响应数据
        String username = req.getParameter("username");
        resp.getWriter().write("hello "+ username + " axios get~");
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String username = req.getParameter("username");
        resp.getWriter().write("hello "+ username + " axios post~");
    }
}

2.2.2 前端实现

<script src="js/axios-0.18.0.js"></script>

<script>
    // // get
    // axios({
    //     method: "get",
    //     url: "http://localhost:8080/ajax-demo/axiosDemo?username=zhangsan"
    // }).then(function (resp) {
    //     alert(resp.data);
    // })

    // post
    axios({
        method: "post",
        url: "http://localhost:8080/ajax-demo/axiosDemo",
        data:"username=zhangsan"
    }).then(function (resp) {
        alert(resp.data);
    })
</script>

2.3 请求方法别名

  • 为了方便起见， Axios 已经为所有支持的请求方法提供了别名。如下：

    • get 请求 ： axios.get(url[,config])

    • delete 请求 ： axios.delete(url[,config])

    • head 请求 ： axios.head(url[,config])

    • options 请求 ： axios.option(url[,config])

    • post 请求：axios.post(url[,data[,config])

    • put 请求：axios.put(url[,data[,config])

    • patch 请求：axios.patch(url[,data[,config])

  • get举例

    axios.get("http://localhost:8080/ajax-demo/axiosServlet?username=zhangsan").then(function (resp) {
    alert(resp.data);
})

  • post举例

    axios.post("http://localhost:8080/ajax-demo/axiosServlet","username=zhangsan").then(function (resp) {
    alert(resp.data);
})

3、 JSON

概念：JavaScript Object Notation。JavaScript 对象表示法

3.1 概述

  • JSON和JS定义对象格式的区别

    • JavaScript

      {
	name:"zhangsan",
	age:23,
	city:"北京"
}

    • JSON

      {
	"name":"zhangsan",
	"age":23,
	"city":"北京"
}

3.2 JSON基础语法

3.2.1 定义格式

  • 基本定义格式

    var 变量名 = '{"key":value,"key":value,...}';

  • value的数据类型

    • 数字（整数或浮点数）
    • 字符串（使用双引号括起来）
    • 逻辑值（true或者false）
    • 数组（在方括号中）
    • 对象（在花括号中）
    • null

  • value的数据类型示例

    var jsonStr = '{"name":"zhangsan","age":23,"addr":["北京","上海","西安"]}'

3.2.2 代码格式

  • 将JSON和JavaScript对象的相互转化

    • parse(str) ：将 JSON串转换为 js 对象。使用方式是： var jsObject = JSON.parse(jsonStr);
    • stringify(obj) ：将 js 对象转换为 JSON 串。使用方式是：var jsonStr = JSON.stringify(jsObject)

  • 代码演示

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>JSON-demo</title>
</head>
<body>
<script>
    // 定义JSON字符串
    var jsonStr = '{"name":"zhangsan","age":23,"addr":["北京","上海","西安"]}'
    alert(jsonStr);

    // 将 JSON 字符串转为 JS 对象
    let jsObject = JSON.parse(jsonStr);
    alert(jsObject)
    alert(jsObject.name)
    // 将 JS 对象转换为 JSON 字符串
    let jsonStr2 = JSON.stringify(jsObject);
    alert(jsonStr2)
</script>
</body>
</html>

3.2.3 发送异步请求携带数据

  • js 提供的 JSON 对象我们只需要了解一下即可。因为 axios 会自动对 js 对象和 JSON 串进行想换转换。
  • 发送异步请求时，如果请求参数是 JSON 格式，那请求方式必须是 POST。因为 JSON 串需要放在请求体中。

  • 使用 axios 发送请求时，如果要携带复杂的数据时都会以 JSON 格式进行传递

    提前定义一个 js 对象，用来封装需要提交的参数，然后使用 JSON.stringify(js对象) 转换为 JSON 串，再将该 JSON 串作为 axios 的 data 属性值进行请求参数的提交

    var jsObject = {name:"张三"};

axios({
    method:"post",
    url:"http://localhost:8080/ajax-demo/axiosServlet",
    data: JSON.stringify(jsObject)
}).then(function (resp) {
    alert(resp.data);
})

  • axios 会自动将 js 对象转换为 JSON 串进行提交

var jsObject = {name:"张三"};

axios({
    method:"post",
    url:"http://localhost:8080/ajax-demo/axiosServlet",
    data:jsObject  //这里 axios 会将该js对象转换为 json 串的
}).then(function (resp) {
    alert(resp.data);
})

3.3 JSON串和Java对象的相互转换

Fastjson 是阿里巴巴提供的一个Java语言编写的高性能功能完善的 JSON 库，是目前Java语言中最快的 JSON 库，可以实现 Java 对象和 JSON 字符串的相互转换。

3.3.1 Fastjson 使用

  • 依赖

    <!-- JSON串和Java对象的相互转换 -->
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>1.2.62</version>
</dependency>

  • Java对象转JSON

    String jsonStr = JSON.toJSONString(obj);

  • JSON转Java对象

    User user = JSON.parseObject(jsonStr, User.class);

3.3.2 代码演示

public class FastJsonDemo {

    public static void main(String[] args) {
        // 将Java对象转为JSON字符串
        User user = new User();
        user.setId(1);
        user.setUsername("zhangsan");
        user.setPassword("123");

        String jsonString = JSON.toJSONString(user);
        System.out.println(jsonString);//{"id":1,"password":"123","username":"zhangsan"}


        // 将JSON字符串转为Java对象
        User u = JSON.parseObject("{\"id\":1,\"password\":\"123\",\"username\":\"zhangsan\"}", User.class);
        System.out.println(u);
    }
}

4、 案例

4.1 需求和方案

  • 需求

    • 使用AJAX+JSON完成品牌数据的查询和添加

  • 方案

    • 查询所有

      1. 页面加载完成后发送异步请求，获取数据列表
      2. controller调用service进行查询
      3. service查询到List集合，返回给controller
      4. controller将List转换为JSON
      5. 将JSON串使用Response写回页面
      6. 遍历字符串数据，展示表格

    • 添加数据

      1. 点击添加按钮跳转到添加信息页面

      2. 输入内容点击提交，将数据封装为JSON格式，使用AJAX发送异步请求到后端

      3. 后端接收数据后反序列化JSON数据

        由于前端提交的是 json 格式的数据，所以我们不能使用 request.getParameter() 方法获取请求参数

        • 如果提交的数据格式是 username=zhangsan&age=23 ，后端就可以使用 request.getParameter() 方法获取
        • 如果提交的数据格式是 json，后端就需要通过 request 对象获取输入流，再通过输入流读取数据

      4. 将获取到的JSON对象转换为Brand对象

      5. 调用Service的add()发明合法添加数据

      6. 将JSON数据返回给浏览器

4.2 查询所有功能

4.2.1 环境准备

  • SQL

    -- 删除tb_brand表
drop table if exists tb_brand;
-- 创建tb_brand表
create table tb_brand
(
    -- id 主键
    id           int primary key auto_increment,
    -- 品牌名称
    brand_name   varchar(20),
    -- 企业名称
    company_name varchar(20),
    -- 排序字段
    ordered      int,
    -- 描述信息
    description  varchar(100),
    -- 状态：0：禁用  1：启用
    status       int
);
-- 添加数据
insert into tb_brand (brand_name, company_name, ordered, description, status)
values ('三只松鼠', '三只松鼠股份有限公司', 5, '好吃不上火', 0),
       ('华为', '华为技术有限公司', 100, '华为致力于把数字世界带入每个人、每个家庭、每个组织，构建万物互联的智能世界', 1),
       ('小米', '小米科技有限公司', 50, 'are you ok', 1);

  • 实体类

    package priv.dandelion.entity;

public class Brand {
    // id 主键
    private Integer id;
    // 品牌名称
    private String brandName;
    // 企业名称
    private String companyName;
    // 排序字段
    private Integer ordered;
    // 描述信息
    private String description;
    // 状态：0：禁用  1：启用
    private Integer status;

    public Brand() {
    }

    public Brand(Integer id, String brandName, String companyName, Integer ordered, String description, Integer status) {
        this.id = id;
        this.brandName = brandName;
        this.companyName = companyName;
        this.ordered = ordered;
        this.description = description;
        this.status = status;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getBrandName() {
        return brandName;
    }

    public void setBrandName(String brandName) {
        this.brandName = brandName;
    }

    public String getCompanyName() {
        return companyName;
    }

    public void setCompanyName(String companyName) {
        this.companyName = companyName;
    }

    public Integer getOrdered() {
        return ordered;
    }

    public void setOrdered(Integer ordered) {
        this.ordered = ordered;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public Integer getStatus() {
        return status;
    }

    public void setStatus(Integer status) {
        this.status = status;
    }

    @Override
    public String toString() {
        return "Brand{" +
                "id=" + id +
                ", brand_name='" + brandName + '\'' +
                ", company_name='" + companyName + '\'' +
                ", ordered=" + ordered +
                ", description='" + description + '\'' +
                ", status=" + status +
                '}';
    }
}

  • MyBatis核心配置文件

    <?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <!--起别名-->
    <typeAliases>
        <package name="priv.dandelion.entity"/>
    </typeAliases>

    <environments default="development">
        <environment id="development">
            <!-- 采用JDBC的事务管理方式 -->
            <transactionManager type="JDBC"/>
            <!-- 数据库连接信息 -->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <!-- value的值一定不能换行，一定！一定！不能换行 -->
                <property name="url" value="jdbc:mysql:///db1?useSSL=false&amp;useUnicode=true&amp;characterEncoding=utf-8&amp;useServerPrepStmts=true"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
    <!-- 扫描mapper，加载SQL映射文件 -->
    <mappers>
        <package name="priv.dandelion.dao"/>
    </mappers>
</configuration>

  • Mapper映射文件

    <?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="priv.dandelion.dao.BrandMapper">

    <!-- 解决数据库与实体类命名不一致问题 -->
    <resultMap id="brandResultMap" type="brand">
        <result column="brand_name" property="brandName"></result>
        <result column="company_name" property="companyName"></result>
    </resultMap>

</mapper>

  • Mapper接口

    package priv.dandelion.dao;

import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.ResultMap;
import org.apache.ibatis.annotations.Select;
import priv.dandelion.entity.Brand;

import java.util.List;


public interface BrandMapper {

    @ResultMap("brandResultMap")
    @Select("select * from tb_brand")
    List<Brand> selectAll();

    @Insert("insert into tb_brand " +
            "values(null, #{brandName}, #{companyName}, " +
            "#{ordered}, #{description}, #{status})")
    void addBrand(Brand brand);
}

  • 工具类 - 获取SqlSession工厂

    package priv.dandelion.utils;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.IOException;
import java.io.InputStream;

public class SqlSessionFactoryUtils {

    // 提升作用域，用于再方法内进行返回
    private static SqlSessionFactory sqlSessionFactory;

    // 静态代码块会随着类的加载自动执行且只执行一次
    static {
        String resource = "mybatis-config.xml";
        InputStream inputStream = null;
        try {
            inputStream = Resources.getResourceAsStream(resource);
        } catch (IOException e) {
            e.printStackTrace();
        }
        sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    }

    public static SqlSessionFactory getSqlSessionFactory() {
        return sqlSessionFactory;
    }

}

  • Service

    package priv.dandelion.service;

import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import priv.dandelion.dao.BrandMapper;
import priv.dandelion.entity.Brand;
import priv.dandelion.utils.SqlSessionFactoryUtils;

import java.util.List;

public class BrandService {
    SqlSessionFactory sqlSessionFactory = SqlSessionFactoryUtils.getSqlSessionFactory();

    public List<Brand> selectAll() {
        SqlSession sqlSession = sqlSessionFactory.openSession();
        BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);
        List<Brand> brands = mapper.selectAll();
        sqlSession.close();
        return brands;
    }

    public void addBrand(Brand brand) {
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);
        mapper.addBrand(brand);
        sqlSession.close();
    }
}

4.2.2 后端实现

  • Servlet

    package priv.dandelion.controller.servlet;

import com.alibaba.fastjson.JSON;
import priv.dandelion.entity.Brand;
import priv.dandelion.service.BrandService;

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.List;

@WebServlet("/selectAll")
public class SelectAllServlet extends HttpServlet {

    BrandService service = new BrandService();

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 调用service 查询
        List<Brand> brands = service.selectAll();
        // 将集合序列化为JSON数据
        String jsonString = JSON.toJSONString(brands);
        // 响应数据
        // 处理中文数据
        resp.setContentType("text/json;charset=utf-8");
        resp.getWriter().write(jsonString);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req, resp);
    }
}

4.2.3 前端实现

  • 引入JS文件

    <script src="js/axios-0.18.0.js"></script>

  • 监听监听页面加载完成事件，在页面加载完成后发送AJAX异步请求

    // 当页面加载完成后发送AJAX请求
window.onload = function () {
    // 发送AJAX请求
    axios({
        method:"get",
        url:"http://localhost:8080//brand-demo-ajax/selectAll"
    }).then(function (resp) {
        // 获取数据
        let brands = resp.data;

        // 表格数据
        let tableData = "<tr>\n" +
            "        <th>序号</th>\n" +
            "        <th>品牌名称</th>\n" +
            "        <th>企业名称</th>\n" +
            "        <th>排序</th>\n" +
            "        <th>品牌介绍</th>\n" +
            "        <th>状态</th>\n" +
            "        <th>操作</th>\n" +
            "    </tr>";

        for (let i = 0; i < brands.length; i++) {
            let brand = brands[i];
            // 对表格数据进行拼接
            tableData += "<tr align=\"center\">\n" +
                "        <td>" + (i + 1) + "</td>\n" +
                "        <td>" + brand.brandName + "</td>\n" +
                "        <td>" + brand.companyName + "</td>\n" +
                "        <td>" + brand.ordered + "</td>\n" +
                "        <td>" + brand.destination + "</td>\n" +
                "        <td>" + brand.status + "</td>\n" +
                "\n" +
                "        <td><a href=\"#\">修改</a> <a href=\"#\">删除</a></td>\n" +
                "    </tr>"
        }

        // 设置表格对象
        document.getElementById("brandTable").innerHTML = tableData;
    })
}

  • 整体页面

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<a href="addBrand.html"><input type="button" value="新增"></a><br>
<hr>
<table id="brandTable" border="1" cellspacing="0" width="100%">

</table>

<script src="js/axios-0.18.0.js"></script>

<script>
    // 当页面加载完成后发送AJAX请求
    window.onload = function () {
        // 发送AJAX请求
        axios({
            method:"get",
            url:"http://localhost:8080//brand-demo-ajax/selectAll"
        }).then(function (resp) {
            // 获取数据
            let brands = resp.data;

            // 表格数据
            let tableData = "<tr>\n" +
                "        <th>序号</th>\n" +
                "        <th>品牌名称</th>\n" +
                "        <th>企业名称</th>\n" +
                "        <th>排序</th>\n" +
                "        <th>品牌介绍</th>\n" +
                "        <th>状态</th>\n" +
                "        <th>操作</th>\n" +
                "    </tr>";

            for (let i = 0; i < brands.length; i++) {
                let brand = brands[i];
                // 对表格数据进行拼接
                tableData += "<tr align=\"center\">\n" +
                    "        <td>" + (i + 1) + "</td>\n" +
                    "        <td>" + brand.brandName + "</td>\n" +
                    "        <td>" + brand.companyName + "</td>\n" +
                    "        <td>" + brand.ordered + "</td>\n" +
                    "        <td>" + brand.destination + "</td>\n" +
                    "        <td>" + brand.status + "</td>\n" +
                    "\n" +
                    "        <td><a href=\"#\">修改</a> <a href=\"#\">删除</a></td>\n" +
                    "    </tr>"
            }

            // 设置表格对象
            document.getElementById("brandTable").innerHTML = tableData;
        })
    }
</script>

</body>
</html>

4.3 添加品牌功能

4.3.1 后端实现

  • Servlet部分

    package priv.dandelion.controller.servlet;

import com.alibaba.fastjson.JSON;
import priv.dandelion.entity.Brand;
import priv.dandelion.service.BrandService;

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.BufferedReader;
import java.io.IOException;

@WebServlet("/add")
public class AddBrandServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        BrandService service = new BrandService();

        // 前端发送为JSON数据，不能使用request.getParameter接收数据

        // 接收前端发送的JSON数据
        BufferedReader reader = req.getReader();
        String params = reader.readLine();

        // 将JSON字符串反序列化为Java对象
        Brand brand = JSON.parseObject(params, Brand.class);

        // 调用Service进行添加
        service.addBrand(brand);
        
        // 响应成功标识
        resp.getWriter().write("success");
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req, resp);
    }
}

4.3.2 前端实现

  • 导入JS

    <script src="js/axios-0.18.0.js"></script>

  • 给提交按钮绑定单击事件，并发送AJAX异步请求到服务器

    // 给按钮绑定单击事件
document.getElementById("btn").onclick = function () {
    // 将表单转换为JSON串
    var formData = {
        brandName:"",
        companyName:"",
        ordered:"",
        description:"",
        status:"",
    };

    // 获取表单数据
    formData.brandName = document.getElementById("brandName").value;
    formData.companyName = document.getElementById("companyName").value;
    formData.description = document.getElementById("description").value;
    formData.ordered = document.getElementById("ordered").value;

    // 获取单选的较为特殊，和单选的性质有关
    let status = document.getElementsByName("status");
    for (let i = 0;i < status.length; i++) {
        if (status[i].checked) {
            formData = status[i].value;
        }
    }
    alert(formData);

    // 发送AJAX请求
    axios({
        method:"post",
        url:"http://localhost:8080//brand-demo-ajax/add",
        data:formData
    }).then(function (resp) {
        alert(resp.data);
        // 判断响应数据是否为success
        if (resp.data == "success") {
            // 重定向到查询所有页面
            location.href = "http://localhost:8080//brand-demo-ajax/brand.html";
        }
    })
}

  • 完整代码

    <!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>添加品牌</title>
</head>
<body>
<h3>添加品牌</h3>
<form action="" method="post">
    品牌名称：<input id="brandName" name="brandName"><br>
    企业名称：<input id="companyName" name="companyName"><br>
    排序：<input id="ordered" name="ordered"><br>
    描述信息：<textarea rows="5" cols="20" id="description" name="description"></textarea><br>
    状态：
    <input type="radio" name="status" value="0">禁用
    <input type="radio" name="status" value="1">启用<br>

    <input type="button" id="btn" value="提交">
</form>

<script src="js/axios-0.18.0.js"></script>

<script>
    // 给按钮绑定单击事件
    document.getElementById("btn").onclick = function () {
        // 将表单转换为JSON串
        var formData = {
          brandName:"",
          companyName:"",
          ordered:"",
          description:"",
          status:"",
        };

        // 获取表单数据
        formData.brandName = document.getElementById("brandName").value;
        formData.companyName = document.getElementById("companyName").value;
        formData.description = document.getElementById("description").value;
        formData.ordered = document.getElementById("ordered").value;

        // 获取单选的较为特殊，和单选的性质有关
        let status = document.getElementsByName("status");
        for (let i = 0;i < status.length; i++) {
            if (status[i].checked) {
                formData = status[i].value;
            }
        }
        alert(formData);

        // 发送AJAX请求
        axios({
            method:"post",
            url:"http://localhost:8080//brand-demo-ajax/add",
            data:formData
        }).then(function (resp) {
            alert(resp.data);
            // 判断响应数据是否为success
            if (resp.data == "success") {
                // 重定向到查询所有页面
                location.href = "http://localhost:8080//brand-demo-ajax/brand.html";
            }
        })
    }
</script>

</body>
</html>

额外说明：

该部分代码略显臃肿，但是该示例的目的主要是对AJAX、Axios以及JSON相关知识点的整理和演示，后续通过前端框架可以大大简化该部分代码。