【JavaWeb-Ajax】网站 --- 通过省份 id 获取省份信息（通过Ajax实现局部刷新）
网站实现功能：
- 通过输入省份编号，应用 Ajax 向服务端（tomcat服务器）发送请求，在服务端从数据库中取出对应信息打回客户端浏览器，局部刷新页面，来获取省份信息（省份名称，省份简称，省份的省会）。
网站结构：
网站预览：
建表语句：
CREATE TABLE `pro` (
`id` int NOT NULL AUTO_INCREMENT,
`name` varchar(255) DEFAULT NULL,
`jiancheng` varchar(255) DEFAULT NULL,
`shenghui` varchar(255) DEFAULT NULL,
PRIMARY KEY (`id`)
);
INSERT INTO `pro` VALUES ('1','河北','冀','石家庄');
INSERT INTO `pro` VALUES ('2','山西','晋','太原市');
INSERT INTO `pro` VALUES ('3','内蒙古','蒙','呼和浩特市');
INSERT INTO `pro` VALUES ('4','辽宁','辽','沈阳');
INSERT INTO `pro` VALUES ('5','江苏','苏','南京');
INSERT INTO `pro` VALUES ('6','浙江','浙','杭州');
INSERT INTO `pro` VALUES ('7','安徽','皖','合肥');
INSERT INTO `pro` VALUES ('8','福建','闽','福州');
INSERT INTO `pro` VALUES ('9','江西','赣','南昌');
index.jsp（网站欢迎资源文件）：
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>$Title$</title>
<%--js代码--%>
<script type="text/javascript">
//定义函数，用来将json中的“value”（省份名称，简称，省份省会）输出到对应的三个文本框中
function callBack(josn) {
document.getElementById("provinceName").value = josn.provinceName;
document.getElementById("provinceJianCheng").value = josn.jianCheng;
document.getElementById("provinceShengHui").value = josn.shengHui;
}
function search() {
//1、创建异步对象
var xmlHttp = new XMLHttpRequest();
//2、绑定事件
xmlHttp.onreadystatechange = function () {
//异步对象把从服务端接受过来的数据处理完 且 网络请求成功 时，执行if内代码
if (xmlHttp.readyState == 4 && xmlHttp.status == 200) {
//通过 xmlHttp.responseText 属性来获取服务端返回的数据
var data = xmlHttp.responseText;
//eval函数，可以将字符串转换为json对象（不重要，不用细研究此函数）
var josnObj = eval("(" + data + ")");
//调用callBack，将jsonObj中的几个“value”写入到对应文本框中
callBack(josnObj);
}
};
//3、初始异步对象的请求参数
//获取provinceId文本框的值
var provinceId = document.getElementById("provinceId").value;
//发送请求（将省份id参数送到服务端）
xmlHttp.open("get", "queryProvinceMessage?provinceId=" + provinceId, true);
//4、发送请求
xmlHttp.send();
}
</script>
</head>
<body>
<p>通过省份ID来获取省份信息</p>
<table>
<tr>
<td>省份编号：</td>
<td>
<input type="text" id="provinceId">
<input type="button" value="搜索" onclick="search()">
</td>
</tr>
<tr>
<td>省份名称：</td>
<td><input type="text" id="provinceName"></td>
</tr>
<tr>
<td>省份简称：</td>
<td><input type="text" id="provinceJianCheng"></td>
</tr>
<tr>
<td>省会名称：</td>
<td><input type="text" id="provinceShengHui"></td>
</tr>
</table>
</body>
</html>
com.burnyouth.util.JdbcUtil（JDBC工具类）：
package com.burnyouth.util;
import java.sql.*;
public class JdbcUtil {
static {
try {
Class.forName("com.mysql.cj.jdbc.Driver");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
private JdbcUtil() {
}
public static Connection getConnection() throws SQLException {
return DriverManager.getConnection("jdbc:mysql://localhost:3306/burning_youth"
, "root", "888");
}
public static void close(Connection connection, Statement statement, ResultSet resultSet) {
if (resultSet != null) {
try {
resultSet.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (statement != null) {
try {
statement.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (connection != null) {
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
com.burnyouth.entity.Province（省份实体类）：
package com.burnyouth.entity;
public class Province {
private Integer provinceId;
private String provinceName;
private String jianCheng;
private String shengHui;
public Province() {
}
public Province(Integer provinceId, String provinceName, String jianCheng, String shengHui) {
this.provinceId = provinceId;
this.provinceName = provinceName;
this.jianCheng = jianCheng;
this.shengHui = shengHui;
}
public Integer getProvinceId() {
return provinceId;
}
public void setProvinceId(Integer provinceId) {
this.provinceId = provinceId;
}
public String getProvinceName() {
return provinceName;
}
public void setProvinceName(String provinceName) {
this.provinceName = provinceName;
}
public String getJianCheng() {
return jianCheng;
}
public void setJianCheng(String jianCheng) {
this.jianCheng = jianCheng;
}
public String getShengHui() {
return shengHui;
}
public void setShengHui(String shengHui) {
this.shengHui = shengHui;
}
}
com.burnyouth.dao.ProvinceDao（连接数据库，进行查询操作并返回数据）：
package com.burnyouth.dao;
import com.burnyouth.entity.Province;
import com.burnyouth.util.JdbcUtil;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
public class ProvinceDao {
public ProvinceDao() {
}
/**
* 通过省份id来获取省份信息
* @param provinceId 省份id
* @return Province对象
*/
public Province queryProvinceById(Integer provinceId) {
Connection connection = null;
PreparedStatement ps = null;
ResultSet resultSet = null;
Province province = null;
try {
connection = JdbcUtil.getConnection();
String sql = "select * from pro where id=?";
ps = connection.prepareStatement(sql);
ps.setInt(1, provinceId);
resultSet = ps.executeQuery();
if (resultSet.next()) {
Integer id = resultSet.getInt("id");
String provinceName = resultSet.getString("name");
String jianCheng = resultSet.getString("jiancheng");
String shengHui = resultSet.getString("shenghui");
province = new Province(id, provinceName, jianCheng, shengHui);
}
} catch (SQLException var10) {
var10.printStackTrace();
} finally {
JdbcUtil.close(connection, ps, resultSet);
}
return province;
}
}
xml：
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="https://jakarta.ee/xml/ns/jakartaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="https://jakarta.ee/xml/ns/jakartaee https://jakarta.ee/xml/ns/jakartaee/web-app_5_0.xsd"
version="5.0">
<servlet>
<servlet-name>QueryProvinceMessageServlet</servlet-name>
<servlet-class>com.burnyouth.controller.QueryProvinceMessageServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>QueryProvinceMessageServlet</servlet-name>
<url-pattern>/queryProvinceMessage</url-pattern>
</servlet-mapping>
</web-app>
com.burnyouth.controller.QueryProvinceMessageServlet（根据请求参数中的省份id，返回对应的 json 格式的省份信息）：
package com.burnyouth.controller;
import com.burnyouth.dao.ProvinceDao;
import com.burnyouth.entity.Province;
import com.fasterxml.jackson.databind.ObjectMapper;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
public class QueryProvinceMessageServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String josn = "";
PrintWriter out = null;
ProvinceDao dao = new ProvinceDao();
//获取省份id参数
String provinceId = req.getParameter("provinceId");
//当省份id不为null 且省份id不为空字符串 时，执行if内代码
if (provinceId != null && provinceId.trim().length() > 0) {
//通过【dao】连接数据库，获取省份信息，并返回具体的省份类
Province province = dao.queryProvinceById(Integer.valueOf(provinceId));
//将字符串转换为json格式的字符串
ObjectMapper objectMapper = new ObjectMapper();
josn = objectMapper.writeValueAsString(province);
}
//使浏览器以正确的编译器读取返回的信息
resp.setContentType("application/json;charset=utf-8");
//获取输出流
out = resp.getWriter();
//返回信息
out.print(josn);
//刷新通道
out.flush();
//关闭通道
out.close();
}
}
