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目录
  • 首先创建 city 和 province 类 给getter setter tostring 以及 构造方法 province类
  • city类
  • 创建 接口 provinceinfodao
  • 实例化对象provinceinfodaoimpl
  • 以及cityinfodao接口
  • cityinfodaoimpl实例化对象
  • findprovinceservlet
  • findcitypidservlet

我只写到了市剩下的区可以复制粘贴的很简单

所需要的jar包有

代码如下

创建数据库

create database provinces character  set utf8;
use provices; 

create table  province (
pid int primary key  auto_increment,
pname varchar(20)
);

insert into province values (null,"河南省");
insert into province values (null,"海南省");
insert into province values (null,"台湾省");
insert into province values (null,"山东省");
insert into province values (null,"河北省");
create table  city (
cid int primary key  auto_increment,
cname varchar(20),
pid int  
);
insert into city values(null,"漯河市",1);
insert into city values(null,"菏泽曹县",4);
insert into city values(null,"高雄市",3);
insert into city values(null,"保定",5);
insert into city values(null,"三亚市",2);

首先创建 city 和 province 类 给getter setter tostring 以及 构造方法 province类

package cn.hp.model;
public class province {
    private  int pid;
    private  string pname;
    public int getpid() {
        return pid;
    }
    public void setpid(int pid) {
        this.pid = pid;
    }
    public string getpname() {
        return pname;
    }
    public void setpname(string pname) {
        this.pname = pname;
    }
    @override
    public string tostring() {
        return "province{" +
                "pid=" + pid +
                ", pname='" + pname + '\'' +
                '}';
    }
    public province(int pid, string pname) {
        this.pid = pid;
        this.pname = pname;
    }
    public province() {
    }
}

city类

package cn.hp.model;
public class city {
    private  int cid;
    private string cname;
    private  int pid;
    public city() {
    }
    public int getcid() {
        return cid;
    }
    @override
    public string tostring() {
        return "city{" +
                "cid=" + cid +
                ", cname='" + cname + '\'' +
                ", pid=" + pid +
                '}';
    }
    public void setcid(int cid) {
        this.cid = cid;
    }
    public string getcname() {
        return cname;
    }
    public city(string cname, int pid) {
        this.cname = cname;
        this.pid = pid;
    }
    public void setcname(string cname) {
        this.cname = cname;
    }
    public int getpid() {
        return pid;
    }
    public void setpid(int pid) {
        this.pid = pid;
    }
    public city(int cid, string cname, int pid) {
        this.cid = cid;
        this.cname = cname;
        this.pid = pid;
    }
}

连接数据库

package cn.hp.util;
import java.sql.connection;
import java.sql.drivermanager;
import java.sql.sqlexception;
public class conndemo {
	private static string driver ="com.mysql.jdbc.driver";
	private static string url = "jdbc:mysql://localhost:3306/provinces?characterencoding=utf8";
	private static string user ="root";
	private static string pwd ="123456";
	public static connection conn;
	public static connection getconn() {
		try {
			class.forname(driver);
			conn = drivermanager.getconnection(url, user, pwd);
		} catch (exception e) {
			// todo auto-generated catch block
			e.printstacktrace();
		}
		return conn;
	}

	public static void getclose() {
		try {
			if (conn != null) {
				conn.close();
			}
		} catch (sqlexception e) {
			// todo auto-generated catch block
			e.printstacktrace();
		}
	}
	// �������ݿ�����
	public static void main(string[] args) {
		system.out.println(getconn());
		if (getconn()!=null) {
			system.out.println("���ӳɹ�");
		}
	}
}

创建 接口 provinceinfodao

package cn.hp.dao;
import cn.hp.model.province;
import java.util.list;
public interface provinceinfodao {
    public  list<province> findall();
}

实例化对象provinceinfodaoimpl

package cn.hp.dao;
import cn.hp.model.province;
import cn.hp.util.conndemo;
import java.sql.connection;
import java.sql.preparedstatement;
import java.sql.resultset;
import java.sql.sqlexception;
import java.util.arraylist;
import java.util.list;
public class provinceinfodaoimpl implements provinceinfodao {
    @override
    public list<province> findall() {
     connection conn=   conndemo.getconn();
     list<province> list= new arraylist<province>();
     string sql="select * from provice";
        try {
            preparedstatement ps= conn.preparestatement(sql);
          resultset rs=  ps.executequery();
          while (rs.next()){
              province p= new province();
              p.setpid(rs.getint(1));
              p.setpname(rs.getstring(2));
              list.add(p);
          }
        } catch (sqlexception e) {
            e.printstacktrace();
        }
        return list;
    }
}

以及cityinfodao接口

package cn.hp.dao;
import cn.hp.model.city;
import java.util.list;
public interface cityinfodao {
    public  list<city>findallcity(int pid);
}

cityinfodaoimpl实例化对象

package cn.hp.dao;
import cn.hp.model.city;
import cn.hp.model.province;
import cn.hp.util.conndemo;
import java.sql.connection;
import java.sql.preparedstatement;
import java.sql.resultset;
import java.sql.sqlexception;
import java.util.arraylist;
import java.util.list;
public class cityinfodaoimpl implements  cityinfodao {
    @override
    public list<city> findallcity(int pid) {
        connection conn=  conndemo.getconn();
        list<city> list= new arraylist<city>();
        string sql="select * from city where pid =?";
        try {
            preparedstatement ps= conn.preparestatement(sql);
            ps.setint(1,pid);
            resultset rs=  ps.executequery();
            while (rs.next()){
                city c= new city();
               c.setcid(rs.getint(1));
               c.setcname(rs.getstring(2));
               c.setpid(rs.getint(3));
                list.add(c);
            }
        } catch (sqlexception e) {
            e.printstacktrace();
        }
        return list;
    }
}

写servlet findprovinceservlet 以及findcitypidservlet

findprovinceservlet

package cn.hp.servlet;
import cn.hp.dao.provinceinfodao;
import cn.hp.dao.provinceinfodaoimpl;
import cn.hp.model.province;
import com.alibaba.fastjson.jsonobject;
import javax.servlet.servletexception;
import javax.servlet.annotation.webservlet;
import javax.servlet.http.httpservlet;
import javax.servlet.http.httpservletrequest;
import javax.servlet.http.httpservletresponse;
import java.io.ioexception;
import java.util.list;
@webservlet("/findprovince")
public class findprovinceservlet extends httpservlet {
    protected void dopost(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {
    }
    protected void doget(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {
        request.setcharacterencoding("utf-8");
        response.setcontenttype("text/html;charset=utf-8");
        provinceinfodao pid=new provinceinfodaoimpl();
        list<province> plist =pid.findall();
        response.getwriter().write(jsonobject.tojsonstring(plist));
    }
}

findcitypidservlet

package cn.hp.servlet;
import cn.hp.dao.cityinfodao;
import cn.hp.dao.cityinfodaoimpl;
import cn.hp.model.city;
import com.alibaba.fastjson.jsonobject;
import javax.servlet.servletexception;
import javax.servlet.annotation.webservlet;
import javax.servlet.http.httpservlet;
import javax.servlet.http.httpservletrequest;
import javax.servlet.http.httpservletresponse;
import java.io.ioexception;
import java.util.list;
@webservlet("/findcitybypid")
public class findcitybypidservlet extends httpservlet {
    protected void dopost(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {
    }
    protected void doget(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {
        request.setcharacterencoding("utf-8");
        response.setcontenttype("text/html;charset=utf-8");
        string id = request.getparameter("id");
        cityinfodao cid= new cityinfodaoimpl();
        list<city> clist  = cid.findallcity(integer.parseint(id));
        response.getwriter().write(jsonobject.tojsonstring(clist));

    }
}

最后是jsp页面

<%@ page contenttype="text/html;charset=utf-8" language="java" %>
<html>
  <head>
    <script src="js/jquery-3.6.0.js"></script>
    <title>$title$</title>
      <script>
          $(function () {
             $.ajax({
                 type:"get",
                 url:"findprovince",
                 datatype:"json",
                 success:function (data) {
                  var obj=  $("#province");
                  for (var i=0;i<data.length;i++){
                      // var  ob= "<option value='+data[i].pid+"'>"+data[i].pname+"</option>"
                      var  ob= "<option value='"+data[i].pid+"'>"+data[i].pname+"</option>"
                      obj.append(ob)
                     }
                 }
             })
          })
      </script>
  </head>
  <body>
   <select name="province" id="province">
     <option value="0">请选择</option>
   </select>省
   <select name="city" id="city">
     <option value="0">请选择</option>
   </select>市
   <select name="street" id="street">
     <option value="0">请选择</option>
   </select>区
  </body>
<script>
    $("#province").change(function () {
       $("#city option").remove();
       $.ajax({
           type:"get",
           url:"findcitybypid?id="+$("#province").val(),
           datatype: "json",
           success:function (data) {
               var obj=  $("#city");
               for (var i=0;i<data.length;i++){
                   var  ob= "<option value='"+data[i].cid+"'>"+data[i].cname+"</option>"
                   obj.append(ob)
               }
           }
       })
    });
</script>
</html>

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