com中的代码.bjpowernode.ajax.servletMyRequestServlet
package com.bjpowernode.ajax.servlet;import com.alibaba.fastjson.JSON;import com.bjpowernode.ajax.bean.Area;import jakarta.servlet.ServletException;import jakarta.servlet.annotation.WebServlet;import jakarta.servlet.http.HttpServlet;import jakarta.servlet.http.HttpServletRequest;import jakarta.servlet.http.HttpServletResponse;import java.io.IOException;import java.sql.*;import java.util.ArrayList;import java.util.List;@WebServlet("/requestservlet")public class MyRequestServlet extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {//获得pcodestring pcode = request.getParameter("pcode");//连接数据库Conection conn = null;PreparedStatement ps = null;ResultSet rs = null;List list = new ArrayList<>();try (//注册驱动Classs.forName("com.mysql.cj.jdbc.Driver");// 连接String url = "jdbc:mysql://localhost:3306/bjpowernode?useUnicode=true&characterEncoding=UTF-8";String user = "root";String password = "lzl";conn = DriverManager.getConnection(url,user,password);//获取预编译对象String sql = "";if(pcode==null){sql="select code,name from t_area where pcode is null";ps = conn.prepareStatement(sql);}else{sql="select code,name from t_area where pcode = ?";ps = conn.prepareStatement(sql);ps.setString(1,pcode);}//执行rs = ps.executeQuery();///处理结果集whilele(rs.next()){String code = rs.getString("code");String name = rs.getString("name");Area a = new Area(code, name);list.add(a);///将包装好的javabean添加到集合} catch (Exception e) {e.printStackTrace();}finally {///关闭连接if(rs!=null){try {rs.close();} catch (SQLException e) {e.printStackTrace();}}if(ps!=null){try {ps.close();} catch (SQLException e) {e.printStackTrace();}}if(conn!=null){try {conn.close();} catch (SQLException e) {e.printStackTrace();}}}response.setContentType("text/json;charset=UTF-8");//集合转换为json格式的数组String json = JSON.toJSONString(list);// 响应JSON。response.getWriter().print(json);}}package com.bjpowernode.ajax.bean;//这是JavaBeanpublic class Area {private String code;private String name;public Area() {}public Area(String code, String name) {this.code = code;this.name = name;}public String getCode() {return code;}public void setCode(String code) {this.code = code;}public String getName() {return name;}public void setName(String name) {this.name = name;}}<!--做省市联动 --><!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><title>做省市联动</title></head><body><script type="text/javascript" src="/ajax/js/jquery-3.4.1.js"></script><script type="text/javascript">///在这里发送ajax请求$(function (){$.ajax({type:"get",url:"/ajax/requestservlet",data:"t="+new Date().getTime(),dataType:"json",async:true,success:function (jsonStr){// [{"code":"001", "name":"河北省"{"code":"002", "name":"河南省"} 我们自己设计了上述格式的json，希望服务器能给我们返回这样一个json格式的字符串。///第一种输出方式/*var html = "<option value=''>--请选择省份--</option>"for(var i = 0;i<jsonStr.length;i++){var Obj = jsonStr[i];html+="<option value='"+Obj.code+"'>"+Obj.name+"</option>"}$("#province").html(html)*////*var html = "<option value=''>--请选择省份--</option>"for(var i = 0;i<jsonStr.length;i++){var Obj = jsonStr[i];html+="<option value='"+Obj.code+"'>"+Obj.name+"</option>()//删除上次输出的旧数据$(”#province").empty();$("#province").append(html)*///第三种$(”#province").empty()var html="<option value=''>--请选择省份--</option>"$("#province").append(html);$.each(jsonStr,function (i,Obj){$("#province").append("<option value='"+Obj.code+"'>"+Obj.name+"</option>()})}//将change绑定到province，以改变事件(”#province").change(function (){//alert(111)//alert(this.value)///只要change发生，发送ajax请求$.ajax({type:"get",async:true,dataType:"json",data:"t="+new Date().getTime()+"&pcode="+this.value,url:"/ajax/requestservlet",success:function (jsonStr){// [{"code":"006", "name":"XXX"},{"code":"008", "name":"YYYY"}///第一个输出方式/*var html="<option value=''>--请选择城市--</option>"for(var i=0;i<jsonStr.length;i++){var Obj = jsonStr[i]html+="<option value='"+Obj.code+"'>"+Obj.name+"</option>"}$("#city").html(html);*////* var html="<option value=''>--请选择城市--</option>"for(var i=0;i<jsonStr.length;i++){var Obj = jsonStr[i]html+="<option value='"+Obj.code+"'>"+Obj.name+"</option>()//删除上次输出的旧数据$(”#city").empty();$("#city").append(html);*///第三种$(”#city").empty()var html="<option value=''>--请选择城市--</option>"$("#city").append(html);$.each(jsonStr,function (i,Obj){$("#city").append("<option value='"+Obj.code+"'>"+Obj.name+"</option>")}}}}}}}}})</script><select id="province"><!--<option value="">--请选择省份--</option><option value="001">河北省</option><option value="002">河南省</option>--></select><select id="city"></select></body></html>
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