ajax与json实现省市二级联动

最新推荐文章于 2020-12-18 11:20:14 发布

popingcrazy

最新推荐文章于 2020-12-18 11:20:14 发布

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CC 4.0 BY-SA版权

文章标签： json ajax import database string exception

本文链接：https://blog.youkuaiyun.com/popingcrazy/article/details/7303735

jsp页面

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
    <base href="<%=basePath%>">

    <title>My JSP 'index.jsp' starting page</title>
   <meta http-equiv="pragma" content="no-cache">
   <meta http-equiv="cache-control" content="no-cache">
   <meta http-equiv="expires" content="0">
   <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
   <meta http-equiv="description" content="This is my page">
   
   <script language="javascript" src="${pageContext.request.contextPath}/js/xmlHttp.js"></script>
<script language="javascript">
function submit(){
   if(document.getElementById('province').options[document.getElementById('province').selectedIndex].value==0){
    alert("请选择省份");
    return false;
   }else{
     createXmlhttp();

      xmlHttp.onreadystatechange= function (){
           if(xmlHttp.readyState==4){
            if(xmlHttp.status==200){
             var json=new Object();
             json=eval("("+xmlHttp.responseText+")");
             //清空上次的记录
             while(document.getElementById('city').options.length>0){
              document.getElementById('city').options.remove(0);
             }
             //动态添加数据
             for(var i=0;i<json.province.length;i++){
              var o=document.createElement('OPTION');
              o.text=json.province[i].city;
              o.value=json.province[i].city;
              document.getElementById('city').add(o);
             }
            }
           }
          }
    xmlHttp.open("post","./servlet/ActionServlet",true);
    xmlHttp.setRequestHeader("Content-Type","application/x-www-form-urlencoded;charset=UTF-8");

    xmlHttp.send("province="+document.getElementById('province').options[document.getElementById('province').selectedIndex].value);
    return true;
   }
}

</script>
</head>

<body>
<select name="province" id="province" onchange="return submit()">
   <option value="0">
    选择省份
   </option>
   <option value="北京">
    北京
   </option>
   <option value="河北 ">
    河北
   </option>
</select>

<select name="city" id="city">
</select>

</body>
</html>
后台页面

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.ResultSet;
import java.sql.SQLException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import cn.csdn.hr.util.Database;

public class ActionServlet extends HttpServlet {

/**
   * @author lixiansheng
   */
   private static final long serialVersionUID = 1L;

public void doGet(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {

this.doPost(request, response);
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {
System.out.println("dopost");
response.setContentType("text/html;charset=utf-8");
request.setCharacterEncoding("utf-8");
PrintWriter out = response.getWriter();
//获取参数
String province=request.getParameter("province");
System.out.println(province);
//查询数据库
System.out.println("asdasd");
Database db=new Database();

ResultSet rs=db.selectDB(province);
//组织JSON字符字面量
StringBuffer info=new StringBuffer();
//JSON格式开始
info.append("{province:[");
try {
   while(rs.next()){
    System.out.println(rs.getString("city"));
    info.append("{city:'");
    info.append(rs.getString("city"));
    info.append("'},");
   }
   //去掉最后那个逗号
   info.delete(info.length()-1,info.length());
   //JSON格式结尾
   info.append("]}");
   rs.close();
   db.closeDB();
} catch (SQLException e) {
   e.printStackTrace();
}
System.out.println(info.toString());
//返回JSON给客户端
out.print(info.toString());
out.flush();
out.close();
}
}

database 数据库连接包
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class Database {
private Connection conn=null;
private PreparedStatement pstmt = null;
private ResultSet rs = null;
private final String URL="jdbc:mysql://localhost:3306/java?user=root&password=1234";

public Database(){
try{
   Class.forName("com.mysql.jdbc.Driver").newInstance();
   this.conn=DriverManager.getConnection(this.URL);
}catch(Exception e){
   e.printStackTrace();
}
}

public ResultSet selectDB(String province){
String sql="select * from address where province=?";
try {
   pstmt = this.conn.prepareStatement(sql);
   pstmt.setString(1,province);
   rs = pstmt.executeQuery();
} catch (SQLException e) {
   e.printStackTrace();
}
return rs;
}

public void closeDB() {
try {
   if (rs != null)
    rs.close();
   if (pstmt != null)
    pstmt.close();
   if (conn != null)
    conn.close();
} catch (Exception e) {
   e.printStackTrace();
}
}
}
在数据库中创建province与city即可