Java web（六）：FilterListenerAJAX

文章目录

一、Filter
- 1.1 基本介绍
- 1.2 过滤器的执行流程
- 1.3 拦截路径配置
- 1.4 过滤器链
- 1.5 案例
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

Java web的三大组件：Servlet、Filter、Listener

一、Filter

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() {}@Overridepublic 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userHttpSession session = req.getSession();Object user = session.getAttribute("user");//3. 判断user是否为nullif(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、Listener

在这里插入图片描述
使用步骤：

实现ServletContextListener接口
添加WebListener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 {@Overrideprotected 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);}@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {this.doGet(request, response);}
}

register.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, IE5xhttp = 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 && 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 Axios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 */
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//# 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. getaxios({method:"get",url:"http://localhost:8080/ajax-demo/axiosServlet?username=zhangsan"}).then(function (resp) {alert(resp.data);})//2. postaxios({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 Fastjson

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。
Fastjson 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 Fastjson 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jsonvar 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 successif(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();@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// Object->JSONList<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);}@Overrideprotected 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();@Overrideprotected 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");}@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {this.doGet(request,response);}
}