Below I will share with you an example of using Ajax and Jquery to cooperate with the database to realize the secondary linkage of the drop-down box. It has a good reference value and I hope it will be helpful to everyone.
First we need to create a database and insert some data into it
We need two tables:
province: Province table
city: City table
as shown in the picture:
Then create the relevant table in java The entity class corresponds to it
Then, we can start the jdbc operation
public class ConnectionFactory {
private static String driver;
private static String url;
private static String user;
private static String password;
static {
Properties prop = new Properties();
//读取文件
try {
InputStream in = ConnectionFactory.class.getResourceAsStream("./jdbc.properties");
prop.load(in);
driver = prop.getProperty("jdbc.driver");
url = prop.getProperty("jdbc.url");
user = prop.getProperty("jdbc.user");
password = prop.getProperty("jdbc.password");
} catch (IOException e) {
e.printStackTrace();
}
}
/**
* 获取连接对象
* @return
*/
public static Connection getConnection(){
Connection conn = null;
try {
Class.forName(driver);
conn = DriverManager.getConnection(url, user, password);
} catch (Exception e) {
throw new RuntimeException(e);
}
return conn;
}
/**
* 关闭资源
* @param conn
* @param pstmt
* @param stmt
* @param rs
*/
public static void close(Connection conn,PreparedStatement pstmt,Statement stmt,ResultSet rs){
try {
if (conn != null) {
conn.close();
}
if (pstmt != null) {
pstmt.close();
}
if (stmt != null) {
stmt.close();
}
if (rs != null) {
rs.close();
}
} catch (SQLException e) {
throw new RuntimeException(e);
}
}First we can get all the provinces when the page is loaded The information, the SQL statement is as follows
Connection conn = null;
PreparedStatement pstmt = null;
Province province2 = null;
@Override
public ArrayList<Province> findAllPro() {
ResultSet rs = null;
ArrayList<Province> pros = null;
try {
String sql = "select id,place from province";
conn = ConnectionFactory.getConnection();
pstmt = conn.prepareStatement(sql);
pros = new ArrayList<Province>();
rs = pstmt.executeQuery();
while(rs.next()){
Province province = new Province();
province.setId(rs.getInt(1));
province.setPlace(rs.getString(2));
pros.add(province);
}
} catch (SQLException e) {
throw new RuntimeException(e);
}
return pros;
}Put the found data into the background and create a SelectedServlet class to receive the queried information about all provinces
response.setContentType("application/json;charset=utf-8");
response.setCharacterEncoding("utf-8");
request.setCharacterEncoding("utf-8");
//创建一个Place对象
ArrayList<Province> pros= new Place().findAllPro();
PrintWriter out = response.getWriter();
//将集合直接转换为Json对象
out.write(JSONArray.fromObject(pros).toString());A collection will be used here To convert Json objects, we need to import the following packages
Then we start writing the front page:
<body>
省份:<select id="province">
<option>--请选择省份--</option>
</select>
城市:<select id="city">
<option>--请选择城市--</option>
</select>
<br/><br/>
<span></span>
</body>Then the jQuery code is as follows: (Since I imported The jQuery version is relatively low, so the method used is getJSON instead of getJson)
$.getJSON("SelectedServlet",function(data,textStatus){
var provinces = data;
var res = "";
for(var i =0;i<provinces.length;i++){
<span style="white-space:pre"> </span>res += "<option>"+provinces[i].place+"</option>";
}
$("#province").append(res);
});This way, the data can be obtained when the page is loaded
Then Let's do linkage again. First, add a change event to the drop-down box, then obtain the selected information, and send the selected information to another CityServlet.
//下拉框改变时触发的事件
$("#province").change(function(){
var seled = $("option:selected").html();
$("span").html(seled);
$.getJSON("CityServlet",{
"province":encodeURI(encodeURI(seled))
},function(data){
$("#city").html("");
var citys = data;
var res = "";
for(var i = 0;i<citys.length;i++){
res += "<option>"+citys[i].place+"</option>";
}
$("#city").append(res);
});
});The server queries the obtained information through sql statements, and the SQL code As follows:
public ArrayList<City> findAllCityByPro(String name) {
ResultSet rs = null;
ArrayList<City> citys = null;
try {
//通过名字获得所有值
String sql = "select c.city_place from city c ,"
+ "province p where c.province_id = "
+ " (select id from province where place = '"+ name +"') "
+ " and c.province_id = p.id";
conn = ConnectionFactory.getConnection();
pstmt = conn.prepareStatement(sql);
citys = new ArrayList<City>();
System.out.println(sql);
rs = pstmt.executeQuery();
while(rs.next()){
City city = new City();
city.setPlace(rs.getString(1));
citys.add(city);
}
System.out.println(citys);
} catch (SQLException e) {
e.printStackTrace();
}
return citys;
}Send the queried data to the background. After receiving the data, the background converts it into a Json object and sends it to the front desk through the callback function. Then the front desk can directly obtain the data through events, and There is no need to jump to various pages, this is Ajax (Asynchronous Javascript And XML),
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("application/json;charset=utf-8");
response.setCharacterEncoding("utf-8");
request.setCharacterEncoding("utf-8");
// String proName = "浙江";
String proName = URLDecoder.decode(URLDecoder.decode(request.getParameter("province"), "utf-8"),
"utf-8");
ArrayList<City> citys= new Place().findAllCityByPro(proName);
PrintWriter out = response.getWriter();
out.write(JSONArray.fromObject(citys).toString());
}As for the code to display the page, it was also written in the jQuery statement earlier
The effect is as follows:
#The above is what I compiled for everyone. I hope it will be helpful to everyone in the future.
Related articles:
How to solve the niceScroll scroll bar misalignment problem in jQuery
How to implement the Baidu search interface in JS
How to implement the double-color ball function in JS
The above is the detailed content of Use Ajax and Jquery to implement secondary linkage of drop-down boxes. For more information, please follow other related articles on the PHP Chinese website!
Scrapy基于Ajax异步加载实现方法Jun 22, 2023 pm 11:09 PMScrapy是一个开源的Python爬虫框架，它可以快速高效地从网站上获取数据。然而，很多网站采用了Ajax异步加载技术，使得Scrapy无法直接获取数据。本文将介绍基于Ajax异步加载的Scrapy实现方法。一、Ajax异步加载原理Ajax异步加载：在传统的页面加载方式中，浏览器发送请求到服务器后，必须等待服务器返回响应并将页面全部加载完毕才能进行下一步操
Nginx中404页面怎么配置及AJAX请求返回404页面May 26, 2023 pm 09:47 PM404页面基础配置404错误是www网站访问容易出现的错误。最常见的出错提示：404notfound。404错误页的设置对网站seo有很大的影响，而设置不当，比如直接转跳主页等，会被搜索引擎降权拔毛。404页面的目的应该是告诉用户：你所请求的页面是不存在的，同时引导用户浏览网站其他页面而不是关掉窗口离去。搜索引擎通过http状态码来识别网页的状态。当搜索引擎获得了一个错误链接时，网站应该返回404状态码，告诉搜索引擎放弃对该链接的索引。而如果返回200或302状态码，搜索引擎就会为该链接建立索引
如何使用CakePHP中的AJAX？Jun 04, 2023 pm 08:01 PM作为一种基于MVC模式的PHP框架，CakePHP已成为许多Web开发人员的首选。它的结构简单，易于扩展，而其中的AJAX技术更是让开发变得更加高效。在本文中，将介绍如何使用CakePHP中的AJAX。什么是AJAX?在介绍如何在CakePHP中使用AJAX之前，我们先来了解一下什么是AJAX。AJAX是“异步JavaScript和XML”的缩写，是指一种在
ajax传递中文乱码怎么办Nov 15, 2023 am 10:42 AMajax传递中文乱码的解决办法：1、设置统一的编码方式；2、服务器端编码；3、客户端解码；4、设置HTTP响应头；5、使用JSON格式。详细介绍：1、设置统一的编码方式，确保服务器端和客户端使用相同的编码方式，通常情况下，UTF-8是一种常用的编码方式，因为它可以支持多种语言和字符集；2、服务器端编码，在服务器端，确保将中文数据以正确的编码方式进行编码，再传递给客户端等等。
jquery ajax报错403怎么办Nov 30, 2022 am 10:09 AMjquery ajax报错403是因为前端和服务器的域名不同而触发了防盗链机制，其解决办法：1、打开相应的代码文件；2、通过“public CorsFilter corsFilter() {...}”方法设置允许的域即可。
什么是ajax重构Jul 01, 2022 pm 05:12 PMajax重构指的是在不改变软件现有功能的基础上，通过调整程序代码改善软件的质量、性能，使其程序的设计模式和架构更合理，提高软件的扩展性和维护性；Ajax的实现主要依赖于XMLHttpRequest对象，由于该对象的实例在处理事件完成后就会被销毁，所以在需要调用它的时候就要重新构建。
在Laravel中如何通过Ajax请求传递CSRF令牌？Sep 10, 2023 pm 03:09 PMCSRF代表跨站请求伪造。CSRF是未经授权的用户冒充授权执行的恶意活动。Laravel通过为每个活动用户会话生成csrf令牌来保护此类恶意活动。令牌存储在用户的会话中。如果会话发生变化，它总是会重新生成，因此每个会话都会验证令牌，以确保授权用户正在执行任何任务。以下是访问csrf_token的示例。生成csrf令牌您可以通过两种方式获取令牌。通过使用$request→session()→token()直接使用csrf_token()方法示例<?phpnamespaceApp\Http\C
使用HTML5文件上传与AJAX和jQuerySep 13, 2023 am 10:09 AM当提交表单时，捕获提交过程并尝试运行以下代码片段来上传文件-//File1varmyFile=document.getElementById('fileBox').files[0];varreader=newFileReader();reader.readAsText(file,'UTF-8');reader.onload=myFunc;functionmyFunc(event){ varres
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
AI Hentai Generator
Generate AI Hentai for free.
Hot Article
Hot Tools
DVWA
Damn Vulnerable Web App (DVWA) is a PHP/MySQL web application that is very vulnerable. Its main goals are to be an aid for security professionals to test their skills and tools in a legal environment, to help web developers better understand the process of securing web applications, and to help teachers/students teach/learn in a classroom environment Web application security. The goal of DVWA is to practice some of the most common web vulnerabilities through a simple and straightforward interface, with varying degrees of difficulty. Please note that this software
Atom editor mac version download
The most popular open source editor
SecLists
SecLists is the ultimate security tester's companion. It is a collection of various types of lists that are frequently used during security assessments, all in one place. SecLists helps make security testing more efficient and productive by conveniently providing all the lists a security tester might need. List types include usernames, passwords, URLs, fuzzing payloads, sensitive data patterns, web shells, and more. The tester can simply pull this repository onto a new test machine and he will have access to every type of list he needs.
Dreamweaver Mac version
Visual web development tools
Zend Studio 13.0.1
Powerful PHP integrated development environment
