省市级联在web前端用户注册使用非常广泛。Ajax异步刷新省市级联。如图：选择不同的区，自动加载相应的街。
<TD class=field>位 置：</TD>
<TD>区：
<SELECT class=text name="district_id" id="district_id">
<option selected value="请选择">请选择</option>
<c:forEach var="district" items="${requestScope.district}">
<OPTION value="${district.id }">${district.district_name }</OPTION>
</c:forEach>
</SELECT>
<span id="street_span">
街：
<SELECT class=text name=street_id id='street_id'>
<c:forEach var='street' items='${sessionScope.street}'>
<OPTION value='${street.street_name}'>${street.street_name}</OPTION></c:forEach>
</SELECT> </span>
</TD>
</TR>
//核心代码（一定要导入jquery-1.8.3.js架包）
<script type="text/javascript">
//声明全局对象
var xmlhttp; //创建XMLHttpRequest对象
function createXMLHttpRequest(){ if(window.XMLHttpRequest){
xmlhttp=new XMLHttpRequest();
}else if(window.ActiveObject){
xmlhttp=new ActiveObject("Microsoft.XMLHTTP");
} }
function doAjax(url){
//初始化XMLHttpRequest
createXMLHttpRequest();
//判断对象是否初始化成功
if(xmlhttp!=null){//说明初始化正常
//请求服务器
xmlhttp.open("post",url,true);
//指定回调函数
xmlhttp.onreadystatechange=successresponse;
xmlhttp.send(null);
}
};
//指定回调函数
function successresponse(){
//判定响应状态
if(xmlhttp.readyState==4){
if(xmlhttp.status==200){
chuli(xmlhttp.responseText);
}
}
};
//初始化加载jQuery
window.onload=function(){
var count=$("#district_id option").length;
for(var i=0;i<count;i++){
if( $("#district_id ").get(0).options[i].selected == true && $("#district_id ").get(0).options[i].value=="请选择"){
$("#street_span").addClass("removeStreet_span");
};
};
};
/*ID选择器*/
$(document).ready(function() {
$("#district_id").change(function(){
var count=$("#district_id option").length;
for(var i=0;i<count;i++){
if( $("#district_id ").get(0).options[i].selected == true && $("#district_id ").get(0).options[i].value=="请选择"){
alert("请选择区");
$("#street_span").addClass("removeStreet_span");
}else if($("#district_id ").get(0).options[i].selected == true){
var district_value=$("#district_id").get(0).options[i].value;
$("#street_span").removeClass("removeStreet_span");
//请求异步刷新：以请求地址作为参数传递
doAjax("../SelectStreetServlet?id="+district_value);
};
};
});
}); function chuli(data){
var json = eval("("+data+")");
var txt = "";
for(var i = 0;i<json.jie.length;i++){
txt = txt+"<option value="+json.jie[i].name+">"+json.jie[i].name+"</option>";
}
$("#street_id").html(txt);
};
</script>
相应的com.msl.Servlet页面
package com.msl.Servlet; import java.io.IOException;
import java.io.Writer;
import java.util.Iterator;
import java.util.Set; import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; import org.hibernate.Session; import com.msl.HibernateUtil.HibernateUtil;
import com.msl.entity.District;
import com.msl.entity.Street; public class SelectStreetServlet extends HttpServlet { /**
*
*/
private static final long serialVersionUID = -3989943574735454346L; /**
* Destruction of the servlet. <br>
*/
public void destroy() {
System.out.println("servlet");
} /**
* The doGet method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request,response);
// response.setContentType("text/html");
// PrintWriter out = response.getWriter();
// out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
// out.println("<HTML>");
// out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>");
// out.println(" <BODY>");
// out.print(" This is ");
// out.print(this.getClass());
// out.println(", using the GET method");
// out.println(" </BODY>");
// out.println("</HTML>");
// out.flush();
// out.close();
} /**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// request.setCharacterEncoding("UTF-8");
// int id=Integer.parseInt(request.getParameter("id"));
//
// StreetBiz sz=new StreetBizImpl();
// List<Street> street=sz.selectStreet(id);
// int status=0;
// if(street.size()>0){
// status=1;
// }
// request.getSession().setAttribute("street", street);
// response.setContentType("text/html");
// response.setCharacterEncoding("UTF-8");
// PrintWriter out = response.getWriter();
// out.println(status);
// out.flush();
// out.close();
request.setCharacterEncoding("UTF-8");
response.setCharacterEncoding("UTF-8");
int id=Integer.parseInt(request.getParameter("id"));
Session session=HibernateUtil.getSession();
District dis=(District) session.get(District.class, id);
Set<Street> st=dis.getSet();
Iterator<Street> it=st.iterator();
StringBuffer s = new StringBuffer("{'jie':["); for(int j = 1;it.hasNext();j++){ Street s1 = it.next(); s.append("{'name':'"+s1.getStreet_name()+"'}"); if(j<st.size()){
s.append(",");
}
} s.append("]}"); Writer out = response.getWriter();
out.write(s.toString());
} /**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occurs
*/
public void init() throws ServletException {
System.out.println("servlet");
} }
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