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() {
    }

    @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、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 {
    @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>
<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, 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 && 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. 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 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);
    }
}