我正在尝试从mysql db填充国家/地区，州和城市，并将它们显示在home.jsp中作为预览，但我遇到了一些错误。
实际上我正在尝试用户注册表单
我有分配了外键和主键的国家/地区，州，城市表 我有3个文件index.jsp，RegistrationController.java，home.jsp用于显示
我只想知道如何在下面的场景中正确地下拉链接国家，城市，州 任何帮助和建议将不胜感激。
index.jsp代码
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<%@ page import="java.sql.*" %>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<script type="text/javascript" src="country-state-dropdown.js"></script>
<title>Registration</title>
<style>
th {
text-align: left
}
</style>
</head>
<body>
<fieldset >
<legend>Registration Form</legend>
<div class="ex">
<form action="RegistrationController" method="post"><!-- action="RegistrationController" -->
<table border="1" align="center" width="50%" cellpadding="5" cellspacing="6">
<tr>
<th>First Name</th>
<td><input type="text" width="auto" name="fn" ></td>
</tr>
<tr>
<th>Last Name</th>
<td><input type="text" name="ln"></td>
</tr>
<tr>
<th>Email</th>
<td><input type="email" name="e" ></td>
</tr>
<tr>
<th>Phone</th>
<td><input type="tel" name="p"></td>
</tr>
<tr>
<th>Gender</th>
<td>
<input type="radio" name="gender" id="male" value="Male">Male
<input type="radio" name="gender" id="female" value="Female">Female
</td>
</tr>
<tr>
<th>Address</th>
<td>
<textarea name="address"></textarea>
</td>
</tr>
<!-- <tr>
<th>Country</th>
<td>
<select name="country" id="countrySel" size="1">
<option value="" selected="selected">-- Select Country --</option>
</select>
</td>
</tr>
<tr>
<th>State</th>
<td>
<select name="state" id="stateSel" size="1">
<option value="" selected="selected">-- Select State --</option>
</select>
</td>
</tr>
<tr>
<th>City</th>
<td>
<select name="city"id="citySel" size="1">
<option value="" selected="selected">-- Select City --</option>
</select>
</td>
</tr>
<tr>
<th>Zip Code</th>
<td>
<select name="zip" id="zipSel" size="1">
<option value="" selected="selected">-- Select Zip --</option>
</select>
</td>
</tr> -->
<tr>
<th>Country</th>
<td>
<select name="country" id="country" onchange="this.form.submit();">
<option value="0">Select Country</option>
<%
try{
String Query="select * from country";
Class.forName("com.mysql.jdbc.Driver");
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/chiru","root","admin123");
Statement st = con.createStatement();
ResultSet rs=st.executeQuery(Query);
while(rs.next()){
%>
<option value="<%=rs.getInt("country_id")%>"
<%
if(request.getParameter("country")!=null)
{
if(rs.getInt("country_id")==Integer.parseInt(request.getParameter("country"))){
out.print("selected");
}
}
%>
><%=rs.getString("country_name")%></option>
<%
}
}catch (Exception ex){
ex.printStackTrace();
}
%>
</select>
</td>
</tr>
<tr>
<th >State</th>
<td>
<select name="state" id="state">
<option value="0">Select State</option>
<%
try{
String Query = "select * from state where country_id=?";
Class.forName("com.mysql.jdbc.Driver");
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/chiru","root","admin123");
PreparedStatement pst = con.prepareStatement(Query);
pst.setString(1, request.getParameter("country"));
ResultSet rs = pst.executeQuery();
while(rs.next()){
%>
<option value="<%=rs.getInt("state_id")%>"><%=rs.getString("state_name")%></option>
<%
}
}catch (Exception ex){
ex.printStackTrace();
}
%>
</select>
</td>
</tr>
<tr>
<th>Status</th>
<td>
<input type="radio" name="status" id="Active" value="Active">Active
<input type="radio" name="status" id="InActive" value="InActive">InActive<br>
</td>
</tr>
</table><br>
<input type="submit" value="Register" style=" margin-left: 45%; padding: 10px; width: auto; background-color:Crimson; color:Cornsilk" />
</form>
</div>
</fieldset>
</body>
</html>
RegistrationController.java代码
package com.registration;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/RegistrationController")
public class RegistrationController extends HttpServlet {
protected void doPost(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
res.setContentType("text/html");
PrintWriter out = res.getWriter();
String fname = req.getParameter("fn");
String lname = req.getParameter("ln");
String email = req.getParameter("e");
String phone = req.getParameter("p");
String sex = req.getParameter("gender");
String address= req.getParameter("address");
String status = req.getParameter("status");
String country = req.getParameter("country");
String state = req.getParameter("state");
/*String city = req.getParameter("city");
String zipcode = req.getParameter("zip");*/
if(fname.isEmpty()||lname.isEmpty()||email.isEmpty() ||
phone.isEmpty()||status.isEmpty()||address.isEmpty()|| country.isEmpty()||state.isEmpty()) //||city.isEmpty()||zipcode.isEmpty()
{
RequestDispatcher rd = req.getRequestDispatcher("index.jsp");
rd.include(req, res);
/*res.sendRedirect("index.jsp");*/
}
else
{
RequestDispatcher rd = req.getRequestDispatcher("home.jsp");
rd.forward(req, res);
/*res.sendRedirect("home.jsp");*/
}
// if(req.getParameter("registrationsuccess").equals("Submit")) {
// RequestDispatcher rd = req.getRequestDispatcher("home.jsp");
// req.setAttribute("message", "Your registration completed successfully !!");
// rd.forward(req, res);
// }
}
}
home.jsp进行预览
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<style>
table#nat {
width: 50%;
background-color: powderblue ;
}
</style>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Preview</title>
</head>
<body>
<%
String fname = request.getParameter("fn");
String lname = request.getParameter("ln");
String email = request.getParameter("e");
String phone = request.getParameter("p");
String sex = request.getParameter("gender");
String address = request.getParameter("address");
String status = request.getParameter("status");
String country = request.getParameter("country");
String state = request.getParameter("state");
/* String city = request.getParameter("city");
String zipcode = request.getParameter("zip"); */
%>
<fieldset>
<legend>Preview of User Data</legend>
<table id="nat" border="1" align="center" width="50%" cellpadding="5" cellspacing="6">
<tr>
<td>First Name</td>
<td><%= fname %></td>
</tr>
<tr>
<td>Last Name</td>
<td><%= lname %></td>
</tr>
<tr>
<td>Email</td>
<td><%= email %></td>
</tr>
<tr>
<td>Phone</td>
<td><%= phone %></td>
</tr>
<tr>
<td>Gender</td>
<td><%= sex%></td>
</tr>
<tr>
<td>Status</td>
<td><%= status%></td>
</tr>
<tr>
<td>Address</td>
<td><%= address %></td>
</tr>
<tr>
<td>Country</td>
<td><%= country%></td>
</tr>
<tr>
<td>State</td>
<td><%= state%></td>
</tr>
<%-- <tr>
<td>City</td>
<td><%= city%></td>
</tr>
<tr>
<td>Zip Code</td>
<td><%= zipcode%></td>
</tr> --%>
<tr>
<td><form action="index.jsp"><input type="submit" value="Go Back" style=" margin-top:18px; padding:10px; color: powderblue; background-color:Green"></form><br></td>
<td><form action="RegistrationSuccess.jsp"><input type= "submit" value="Submit" style= " padding:10px; color: powderblue; background-color:Green"></form></td>
</tr>
<!-- <tr>
<td>
</td>
</tr> -->
</table>