Java web（六）：Filter&Listener&AJAX

本文介绍: 过滤器可以把对资源的请求拦截下来，从而实现一些特殊的功能。过滤器一般完成一些通用的操作：权限控制、统一编码处理、敏感字符处理等实现Fi lte r 接口添加We bFi lte r 注解，并配置拦截路径实现doFi lter方法@We bFilt er(“/*”) // 拦截所有页面@Ov err ide// 1.当出现以下资源可以放行//判断访问资源路径是否和登录注册相关// 获取当前访问的资源路径//循环判断//找到了//放行//break;return;

文章 目录

一、Filter
二、Listener
三、AJAX
- 3.1 快速入门
- 3.2 Axios异步框架
四、 JSON
- 4.1 JSON基础语法
- 4.2 Fastjson
五、案例JSON+Axios+Servlet

Jav a web的三大组件：Serv let、Filt er、Li ste n er

一、Filt er

1.1 基本 介绍

过滤器可以把对资源的请求拦截下来，从而实现一些特殊的功能。过滤器一般完成一些通用的操作：权限控制、统一编码处理、敏感字符处理等

使用步骤：

实现Filter接口
添加WebFilter注解，并配置拦截路径
实现doFilter方法

@WebFilter("/*") // 拦截所有页面
public class LoginFilter implements Filter {
    public void init(FilterConfig config) throws ServletException {
    }

    public void destroy() {
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws ServletException, IOException {
        HttpServletRequest req = (HttpServletRequest) request;
        // 1.当出现以下资源可以放行
        //判断访问资源路径是否和登录注册相关
        String[] urls = {"/login.jsp","/imgs/","/css/","/loginServlet","/register.jsp","/registerServlet","/checkCodeServlet"};
        // 获取当前访问的资源路径
        String url = req.getRequestURL().toString();

        //循环判断
        for (String u : urls) {
            if(url.contains(u)){
                //找到了
                //放行
                chain.doFilter(request, response);
                //break;
                return;
            }
        }

        //2. 判断session中是否有user
        HttpSession session = req.getSession();
        Object user = session.getAttribute("user");

        //3. 判断user是否为null
        if(user != null){
            // 登录过了
            //放行
            chain.doFilter(request, response);
        }else {
            // 没有登陆，存储提示信息，跳转到登录页面
            
            req.setAttribute("login_msg","您尚未登陆！");
            req.getRequestDispatcher("/login.jsp").forward(req,response);
        }
    }
}

1.2 过滤器的执行 流程

在这里插入图片描述

1.3 拦截路径配置

在这里插入图片描述

1.4 过滤器链

在这里插入图片描述

1.5 案例

二、Liste ner

在这里插入图片描述
使用步骤：

实现ServletCon textListe ner接口
添加WebListe ner注解
实现接口方法

三、AJAX

3.1 快速 入门

在这里插入图片描述

SelectUserServlet.java

@WebServlet("/selectUserServlet")
public class SelectUserServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1. 接收用户名
        String username = request.getParameter("username");
        //2. 调用service查询User对象
        boolean flag = true;
        //3. 响应标记
        response.getWriter().write("" + flag);
    }

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

register.html

<!DOCTYPE html&gt;
<html lang="en"&gt;
<head&gt;
    <meta charset="UTF-8"&gt;
    <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">用户名已存在</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>

<script>

    //1. 给用户名输入框绑定 失去焦点事件
    document.getElementById("username").onblur = function () {
        //2. 发送ajax请求
        // 获取用户名的值
        var username = this.value;

        //2.1. 创建核心对象
        var xhttp;
        if (window.XMLHttpRequest) {
            xhttp = new XMLHttpRequest();
        } else {
            // code for IE6, IE5
            xhttp = new ActiveXObject("Microsoft.XMLHTTP");
        }
        //2.2. 发送请求
        xhttp.open("GET", "http://localhost:8080/ajax-demo/selectUserServlet?username="+username);
        xhttp.send();

        //2.3. 获取响应
        xhttp.onreadystatechange = function() {
            if (this.readyState == 4 &amp;&amp; this.status == 200) {
                //alert(this.responseText);
                //判断
                if(this.responseText == "true"){
                    //用户名存在，显示提示信息
                    document.getElementById("username_err").style.display = '';
                }else {
                    //用户名不存在 ，清楚提示信息
                    document.getElementById("username_err").style.display = 'none';
                }
            }
        };

    }

</script>
</body>
</html>

3.2 Ax ios 异步 框架

Axios对AJAX的代码进行封装，简化代码书写。

axios-0.18.0.js

/* axios v0.18.0 | (c) 2018 by Matt Zabriskie */
!function(e,t){"object"==typeof exports&amp;&amp;"object"==typeof module?module.exports=t():"function"==typeof define&amp;&amp;define.amd?define([],t):"object"==typeof exports?exports.axios=t():e.axios=t()}(this,function(){return function(e){function t(r){if(n[r])return n[r].exports;var o=n[r]={exports:{},id:r,loaded:!1};return e[r].call(o.exports,o,o.exports,t),o.loaded=!0,o.exports}var n={};return t.m=e,t.c=n,t.p="",t(0)}([function(e,t,n){e.exports=n(1)},function(e,t,n){"use strict";function r(e){var t=new s(e),n=i(s.prototype.request,t);return o.extend(n,s.prototype,t),o.extend(n,t),n}var o=n(2),i=n(3),s=n(5),u=n(6),a=r(u);a.Axios=s,a.create=function(e){return r(o.merge(u,e))},a.Cancel=n(23),a.CancelToken=n(24),a.isCancel=n(20),a.all=function(e){return Promise.all(e)},a.spread=n(25),e.exports=a,e.exports.default=a},function(e,t,n){"use strict";function r(e){return"[object Array]"===R.call(e)}function o(e){return"[object ArrayBuffer]"===R.call(e)}function i(e){return"undefined"!=typeof FormData&amp;&amp;e instanceof FormData}function s(e){var t;return t="undefined"!=typeof ArrayBuffer&amp;&amp;ArrayBuffer.isView?ArrayBuffer.isView(e):e&&e.buffer&&e.buffer instanceof ArrayBuffer}function u(e){return"string"==typeof e}function a(e){return"number"==typeof e}function c(e){return"undefined"==typeof e}function f(e){return null!==e&&"object"==typeof e}function p(e){return"[object Date]"===R.call(e)}function d(e){return"[object File]"===R.call(e)}function l(e){return"[object Blob]"===R.call(e)}function h(e){return"[object Function]"===R.call(e)}function m(e){return f(e)&&h(e.pipe)}function y(e){return"undefined"!=typeof URLSearchParams&&e instanceof URLSearchParams}function w(e){return e.replace(/^s*/,"").replace(/s*$/,"")}function g(){return("undefined"==typeof navigator||"ReactNative"!==navigator.product)&&("undefined"!=typeof window&&"undefined"!=typeof document)}function v(e,t){if(null!==e&&"undefined"!=typeof e)if("object"!=typeof e&&(e=[e]),r(e))for(var n=0,o=e.length;n<o;n++)t.call(null,e[n],n,e);else for(var i in e)Object.prototype.hasOwnProperty.call(e,i)&&t.call(null,e[i],i,e)}function x(){function e(e,n){"object"==typeof t[n]&&"object"==typeof e?t[n]=x(t[n],e):t[n]=e}for(var t={},n=0,r=arguments.length;n<r;n++)v(arguments[n],e);return t}function b(e,t,n){return v(t,function(t,r){n&&"function"==typeof t?e[r]=E(t,n):e[r]=t}),e}var E=n(3),C=n(4),R=Object.prototype.toString;e.exports={isArray:r,isArrayBuffer:o,isBuffer:C,isFormData:i,isArrayBufferView:s,isString:u,isNumber:a,isObject:f,isUndefined:c,isDate:p,isFile:d,isBlob:l,isFunction:h,isStream:m,isURLSearchParams:y,isStandardBrowserEnv:g,forEach:v,merge:x,extend:b,trim:w}},function(e,t){"use strict";e.exports=function(e,t){return function(){for(var n=new Array(arguments.length),r=0;r<n.length;r++)n[r]=arguments[r];return e.apply(t,n)}}},function(e,t){function n(e){return!!e.constructor&&"function"==typeof e.constructor.isBuffer&&e.constructor.isBuffer(e)}function r(e){return"function"==typeof e.readFloatLE&&"function"==typeof e.slice&&n(e.slice(0,0))}/*!
 * Determine if an object is a Buffer
 *
 * @author   Feross Aboukhadijeh <https://feross.org>
 * @license  MIT
 */
    e.exports=function(e){return null!=e&&(n(e)||r(e)||!!e._isBuffer)}},function(e,t,n){"use strict";function r(e){this.defaults=e,this.interceptors={request:new s,response:new s}}var o=n(6),i=n(2),s=n(17),u=n(18);r.prototype.request=function(e){"string"==typeof e&&(e=i.merge({url:arguments[0]},arguments[1])),e=i.merge(o,{method:"get"},this.defaults,e),e.method=e.method.toLowerCase();var t=[u,void 0],n=Promise.resolve(e);for(this.interceptors.request.forEach(function(e){t.unshift(e.fulfilled,e.rejected)}),this.interceptors.response.forEach(function(e){t.push(e.fulfilled,e.rejected)});t.length;)n=n.then(t.shift(),t.shift());return n},i.forEach(["delete","get","head","options"],function(e){r.prototype[e]=function(t,n){return this.request(i.merge(n||{},{method:e,url:t}))}}),i.forEach(["post","put","patch"],function(e){r.prototype[e]=function(t,n,r){return this.request(i.merge(r||{},{method:e,url:t,data:n}))}}),e.exports=r},function(e,t,n){"use strict";function r(e,t){!i.isUndefined(e)&&i.isUndefined(e["Content-Type"])&&(e["Content-Type"]=t)}function o(){var e;return"undefined"!=typeof XMLHttpRequest?e=n(8):"undefined"!=typeof process&&(e=n(8)),e}var i=n(2),s=n(7),u={"Content-Type":"application/x-www-form-urlencoded"},a={adapter:o(),transformRequest:[function(e,t){return s(t,"Content-Type"),i.isFormData(e)||i.isArrayBuffer(e)||i.isBuffer(e)||i.isStream(e)||i.isFile(e)||i.isBlob(e)?e:i.isArrayBufferView(e)?e.buffer:i.isURLSearchParams(e)?(r(t,"application/x-www-form-urlencoded;charset=utf-8"),e.toString()):i.isObject(e)?(r(t,"application/json;charset=utf-8"),JSON.stringify(e)):e}],transformResponse:[function(e){if("string"==typeof e)try{e=JSON.parse(e)}catch(e){}return e}],timeout:0,xsrfCookieName:"XSRF-TOKEN",xsrfHeaderName:"X-XSRF-TOKEN",maxContentLength:-1,validateStatus:function(e){return e>=200&&e<300}};a.headers={common:{Accept:"application/json, text/plain, */*"}},i.forEach(["delete","get","head"],function(e){a.headers[e]={}}),i.forEach(["post","put","patch"],function(e){a.headers[e]=i.merge(u)}),e.exports=a},function(e,t,n){"use strict";var r=n(2);e.exports=function(e,t){r.forEach(e,function(n,r){r!==t&&r.toUpperCase()===t.toUpperCase()&&(e[t]=n,delete e[r])})}},function(e,t,n){"use strict";var r=n(2),o=n(9),i=n(12),s=n(13),u=n(14),a=n(10),c="undefined"!=typeof window&&window.btoa&&window.btoa.bind(window)||n(15);e.exports=function(e){return new Promise(function(t,f){var p=e.data,d=e.headers;r.isFormData(p)&&delete d["Content-Type"];var l=new XMLHttpRequest,h="onreadystatechange",m=!1;if("undefined"==typeof window||!window.XDomainRequest||"withCredentials"in l||u(e.url)||(l=new window.XDomainRequest,h="onload",m=!0,l.onprogress=function(){},l.ontimeout=function(){}),e.auth){var y=e.auth.username||"",w=e.auth.password||"";d.Authorization="Basic "+c(y+":"+w)}if(l.open(e.method.toUpperCase(),i(e.url,e.params,e.paramsSerializer),!0),l.timeout=e.timeout,l[h]=function(){if(l&&(4===l.readyState||m)&&(0!==l.status||l.responseURL&&0===l.responseURL.indexOf("file:"))){var n="getAllResponseHeaders"in l?s(l.getAllResponseHeaders()):null,r=e.responseType&&"text"!==e.responseType?l.response:l.responseText,i={data:r,status:1223===l.status?204:l.status,statusText:1223===l.status?"No Content":l.statusText,headers:n,config:e,request:l};o(t,f,i),l=null}},l.onerror=function(){f(a("Network Error",e,null,l)),l=null},l.ontimeout=function(){f(a("timeout of "+e.timeout+"ms exceeded",e,"ECONNABORTED",l)),l=null},r.isStandardBrowserEnv()){var g=n(16),v=(e.withCredentials||u(e.url))&&e.xsrfCookieName?g.read(e.xsrfCookieName):void 0;v&&(d[e.xsrfHeaderName]=v)}if("setRequestHeader"in l&&r.forEach(d,function(e,t){"undefined"==typeof p&&"content-type"===t.toLowerCase()?delete d[t]:l.setRequestHeader(t,e)}),e.withCredentials&&(l.withCredentials=!0),e.responseType)try{l.responseType=e.responseType}catch(t){if("json"!==e.responseType)throw t}"function"==typeof e.onDownloadProgress&&l.addEventListener("progress",e.onDownloadProgress),"function"==typeof e.onUploadProgress&&l.upload&&l.upload.addEventListener("progress",e.onUploadProgress),e.cancelToken&&e.cancelToken.promise.then(function(e){l&&(l.abort(),f(e),l=null)}),void 0===p&&(p=null),l.send(p)})}},function(e,t,n){"use strict";var r=n(10);e.exports=function(e,t,n){var o=n.config.validateStatus;n.status&&o&&!o(n.status)?t(r("Request failed with status code "+n.status,n.config,null,n.request,n)):e(n)}},function(e,t,n){"use strict";var r=n(11);e.exports=function(e,t,n,o,i){var s=new Error(e);return r(s,t,n,o,i)}},function(e,t){"use strict";e.exports=function(e,t,n,r,o){return e.config=t,n&&(e.code=n),e.request=r,e.response=o,e}},function(e,t,n){"use strict";function r(e){return encodeURIComponent(e).replace(/%40/gi,"@").replace(/%3A/gi,":").replace(/%24/g,"$").replace(/%2C/gi,",").replace(/%20/g,"+").replace(/%5B/gi,"[").replace(/%5D/gi,"]")}var o=n(2);e.exports=function(e,t,n){if(!t)return e;var i;if(n)i=n(t);else if(o.isURLSearchParams(t))i=t.toString();else{var s=[];o.forEach(t,function(e,t){null!==e&&"undefined"!=typeof e&&(o.isArray(e)?t+="[]":e=[e],o.forEach(e,function(e){o.isDate(e)?e=e.toISOString():o.isObject(e)&&(e=JSON.stringify(e)),s.push(r(t)+"="+r(e))}))}),i=s.join("&")}return i&&(e+=(e.indexOf("?")===-1?"?":"&")+i),e}},function(e,t,n){"use strict";var r=n(2),o=["age","authorization","content-length","content-type","etag","expires","from","host","if-modified-since","if-unmodified-since","last-modified","location","max-forwards","proxy-authorization","referer","retry-after","user-agent"];e.exports=function(e){var t,n,i,s={};return e?(r.forEach(e.split("n"),function(e){if(i=e.indexOf(":"),t=r.trim(e.substr(0,i)).toLowerCase(),n=r.trim(e.substr(i+1)),t){if(s[t]&&o.indexOf(t)>=0)return;"set-cookie"===t?s[t]=(s[t]?s[t]:[]).concat([n]):s[t]=s[t]?s[t]+", "+n:n}}),s):s}},function(e,t,n){"use strict";var r=n(2);e.exports=r.isStandardBrowserEnv()?function(){function e(e){var t=e;return n&&(o.setAttribute("href",t),t=o.href),o.setAttribute("href",t),{href:o.href,protocol:o.protocol?o.protocol.replace(/:$/,""):"",host:o.host,search:o.search?o.search.replace(/^?/,""):"",hash:o.hash?o.hash.replace(/^#/,""):"",hostname:o.hostname,port:o.port,pathname:"/"===o.pathname.charAt(0)?o.pathname:"/"+o.pathname}}var t,n=/(msie|trident)/i.test(navigator.userAgent),o=document.createElement("a");return t=e(window.location.href),function(n){var o=r.isString(n)?e(n):n;return o.protocol===t.protocol&&o.host===t.host}}():function(){return function(){return!0}}()},function(e,t){"use strict";function n(){this.message="String contains an invalid character"}function r(e){for(var t,r,i=String(e),s="",u=0,a=o;i.charAt(0|u)||(a="=",u%1);s+=a.charAt(63&t>>8-u%1*8)){if(r=i.charCodeAt(u+=.75),r>255)throw new n;t=t<<8|r}return s}var o="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";n.prototype=new Error,n.prototype.code=5,n.prototype.name="InvalidCharacterError",e.exports=r},function(e,t,n){"use strict";var r=n(2);e.exports=r.isStandardBrowserEnv()?function(){return{write:function(e,t,n,o,i,s){var u=[];u.push(e+"="+encodeURIComponent(t)),r.isNumber(n)&&u.push("expires="+new Date(n).toGMTString()),r.isString(o)&&u.push("path="+o),r.isString(i)&&u.push("domain="+i),s===!0&&u.push("secure"),document.cookie=u.join("; ")},read:function(e){var t=document.cookie.match(new RegExp("(^|;\s*)("+e+")=([^;]*)"));return t?decodeURIComponent(t[3]):null},remove:function(e){this.write(e,"",Date.now()-864e5)}}}():function(){return{write:function(){},read:function(){return null},remove:function(){}}}()},function(e,t,n){"use strict";function r(){this.handlers=[]}var o=n(2);r.prototype.use=function(e,t){return this.handlers.push({fulfilled:e,rejected:t}),this.handlers.length-1},r.prototype.eject=function(e){this.handlers[e]&&(this.handlers[e]=null)},r.prototype.forEach=function(e){o.forEach(this.handlers,function(t){null!==t&&e(t)})},e.exports=r},function(e,t,n){"use strict";function r(e){e.cancelToken&&e.cancelToken.throwIfRequested()}var o=n(2),i=n(19),s=n(20),u=n(6),a=n(21),c=n(22);e.exports=function(e){r(e),e.baseURL&&!a(e.url)&&(e.url=c(e.baseURL,e.url)),e.headers=e.headers||{},e.data=i(e.data,e.headers,e.transformRequest),e.headers=o.merge(e.headers.common||{},e.headers[e.method]||{},e.headers||{}),o.forEach(["delete","get","head","post","put","patch","common"],function(t){delete e.headers[t]});var t=e.adapter||u.adapter;return t(e).then(function(t){return r(e),t.data=i(t.data,t.headers,e.transformResponse),t},function(t){return s(t)||(r(e),t&&t.response&&(t.response.data=i(t.response.data,t.response.headers,e.transformResponse))),Promise.reject(t)})}},function(e,t,n){"use strict";var r=n(2);e.exports=function(e,t,n){return r.forEach(n,function(n){e=n(e,t)}),e}},function(e,t){"use strict";e.exports=function(e){return!(!e||!e.__CANCEL__)}},function(e,t){"use strict";e.exports=function(e){return/^([a-z][a-zd+-.]*:)?///i.test(e)}},function(e,t){"use strict";e.exports=function(e,t){return t?e.replace(//+$/,"")+"/"+t.replace(/^/+/,""):e}},function(e,t){"use strict";function n(e){this.message=e}n.prototype.toString=function(){return"Cancel"+(this.message?": "+this.message:"")},n.prototype.__CANCEL__=!0,e.exports=n},function(e,t,n){"use strict";function r(e){if("function"!=typeof e)throw new TypeError("executor must be a function.");var t;this.promise=new Promise(function(e){t=e});var n=this;e(function(e){n.reason||(n.reason=new o(e),t(n.reason))})}var o=n(23);r.prototype.throwIfRequested=function(){if(this.reason)throw this.reason},r.source=function(){var e,t=new r(function(t){e=t});return{token:t,cancel:e}},e.exports=r},function(e,t){"use strict";e.exports=function(e){return function(t){return e.apply(null,t)}}}])});
//# sourceMappingURL=axios.min.map

使用步骤：

引入 axios.js 文件

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

使用axios发送请求并获取响应结果

<script>
	// 第一种方式
    //1. get
   axios({
        method:"get",
        url:"http://localhost:8080/ajax-demo/axiosServlet?username=zhangsan"
    }).then(function (resp) {
        alert(resp.data);
    })


    //2. post
    axios({
        method:"post",
        url:"http://localhost:8080/ajax-demo/axiosServlet",
        data:"username=zhangsan"
    }).then(function (resp) {
        alert(resp.data);
    })

	// 也可以这么写
	var jsObject = {name:"zhangsan"};
    axios({
        method:"post",
        url:"http://localhost:8080/ajax-demo/axiosServlet",
        data:jsObject
    }).then(function (resp) {
        alert(resp.data);
    })
	
	// 第二种方式
 	axios.get("http://localhost:8080/ajax-demo/axiosServlet?username=zhangsan").then(function (resp) {
        alert(resp.data);
    })

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

    
</script>

四、 JSON

4.1 JSON基础语法

在这里插入图片描述

4.2 Fast json

Fast json 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。
Fast json 使用也是比较简单的，分为以下三步完成

导入坐标

<dependency>
	<groupId>com.alibaba</groupId>
	<artifactId>fastjson</artifactId>
	<version>1.2.62</version>
</dependency>

Java对象转JSON

String jsonStr = JSON.toJSONString(obj);

将 Java 对象转换为 JSON 串，只需要使用 Fast json 提供的 JSON 类中的 toJSONString() 静态方法即可。

JSON字符串转Java对象

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

将 json 转换为 Java 对象，只需要使用 Fastjson 提供的 JSON 类中的 parseObject() 静态方法即可。

五、案例JSON+Axios+Servlet

使用JSON+Axios完成查看全部数据和添加数据

brand.html 显示数据

<!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%">
    <tr>
        <th>序号</th>
        <th>品牌名称</th>
        <th>企业名称</th>
        <th>排序</th>
        <th>品牌介绍</th>
        <th>状态</th>
        <th>操作</th>
    </tr>
    <tr align="center">
        <td>1</td>
        <td>三只松鼠</td>
        <td>三只松鼠</td>
        <td>100</td>
        <td>三只松鼠，好吃不上火</td>
        <td>启用</td>
        <td><a href="#">修改</a> <a href="#">删除</a></td>
    </tr>

    <tr align="center">
        <td>2</td>
        <td>优衣库</td>
        <td>优衣库</td>
        <td>10</td>
        <td>优衣库，服适人生</td>
        <td>禁用</td>

        <td><a href="#">修改</a> <a href="#">删除</a></td>
    </tr>

    <tr align="center">
        <td>3</td>
        <td>小米</td>
        <td>小米科技有限公司</td>
        <td>1000</td>
        <td>为发烧而生</td>
        <td>启用</td>

        <td><a href="#">修改</a> <a href="#">删除</a></td>
    </tr>
</table>

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

<script>
    //1. 当页面加载完成后，发送ajax请求
    window.onload = function () {
        //2. 发送ajax请求
        axios({
            method:"get",
            url:"http://localhost:8080/ajax-demo/selectAllServlet"
        }).then(function (resp) {
            //获取数据
            let brands = resp.data;
            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];

                tableData += "n" +
                    "    <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.description+"</td>n" +
                    "        <td>"+brand.status+"</td>n" +
                    "n" +
                    "        <td><a href="#">修改</a> <a href="#">删除</a></td>n" +
                    "    </tr>";
            }

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



</script>


</body>
</html>

addBrand.html 添加数据

<!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>
    //1. 给按钮绑定单击事件
    document.getElementById("btn").onclick = function () {
        // 将表单数据转为json
        var formData = {
            brandName:"",
            companyName:"",
            ordered:"",
            description:"",
            status:"",
        };
        // 获取表单数据
        let brandName = document.getElementById("brandName").value;
        // 设置数据
        formData.brandName = brandName;

        // 获取表单数据
        let companyName = document.getElementById("companyName").value;
        // 设置数据
        formData.companyName = companyName;

        // 获取表单数据
        let ordered = document.getElementById("ordered").value;
        // 设置数据
        formData.ordered = ordered;

        // 获取表单数据
        let description = document.getElementById("description").value;
        // 设置数据
        formData.description = description;

        let status = document.getElementsByName("status");
        for (let i = 0; i < status.length; i++) {
            if(status[i].checked){
                //
                formData.status = status[i].value ;
            }
        }

        console.log(formData);
        //2. 发送ajax请求
        axios({
            method:"post",
            url:"http://localhost:8080/ajax-demo/addServlet",
            data:formData
        }).then(function (resp) {
            // 判断响应数据是否为 success
            if(resp.data == "success"){
                location.href = "http://localhost:8080/ajax-demo/brand.html";
            }
        })
    }

</script>
</body>
</html>

SelectAllServelt.java

@WebServlet("/selectAllServlet")
public class SelectAllServelt extends HttpServlet {
    private BrandService brandService = new BrandService();
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // Object->JSON
        List<Brand> brands = brandService.selectAll();
        String s = JSON.toJSONString(brands);
        // 解决中文乱码
        response.setContentType("text/json;charset=utf-8");
        // 响应数据
        response.getWriter().write(s);
    }

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

AddServlet.java

@WebServlet("/addServlet")
public class AddServlet extends HttpServlet {
    private BrandService brandService = new BrandService();
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1. 接收数据,request.getParameter 不能接收json的数据
       /* String brandName = request.getParameter("brandName");
        System.out.println(brandName);*/

        // 获取请求体数据
        BufferedReader br = request.getReader();
        String params = br.readLine();

        // 将JSON字符串转为Java对象
        Brand brand = JSON.parseObject(params, Brand.class);


        //2. 调用service 添加
        brandService.add(brand);

        //3. 响应成功标识
        response.getWriter().write("success");

    }

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