Java web（六）：Filter&Listener&AJAX
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() {
}
@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
1.3 拦截路径配置
1.4 过滤器链
1.5 案例
二、Listener
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
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
欢迎注册
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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* Determine if an object is a Buffer
*
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*/
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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. 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
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 = " \n" +
" 序号 \n" +
" 品牌名称 \n" +
" 企业名称 \n" +
" 排序 \n" +
" 品牌介绍 \n" +
" 状态 \n" +
" 操作 \n" +
" ";
for (let i = 0; i < brands.length ; i++) {
let brand = brands[i];
tableData += "\n" +
" \n" +
" "+(i+1)+" \n" +
" "+brand.brandName+" \n" +
" "+brand.companyName+" \n" +
" "+brand.ordered+" \n" +
" "+brand.description+" \n" +
" "+brand.status+" \n" +
"\n" +
" 修改 删除 \n" +
" ";
}
// 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);
}
}