想来有利有弊，不知怎么权衡，求有经验的大侠指导
一般都是后台直接拼接好JSON格式返回，页面解析。
给你看个例子：
<%@ page language="java" contentType="text/html; charset=GB18030"
pageEncoding="GB18030"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=GB18030">
<title>四级联动下拉列表选中值保持不变</title>
<style type="text/css">
div #tip {
font:consolas normal 20px;
color:blue;
}
</style>
<裤握局script type="text/javascript" src="js/jquery-1.4.4.min.js"></script>
<script type="胡让text/javascript">
$(function() {
$("#province").change(function() {
if ($("#province").val() == '0') {
$("#city").html('');
$("#county").html('');
$("#town").html('');
return;
}
$("#tip").append("<span>请求Ajax获取城市...<br></span>");
$.get("ajax.do",
{type:'1',
value:$("#province").val(),
time:new Date()
},function(data) {
$("#tip").append("<span>"+$("#province").val()+"下城市信息获取成功<br></span>");
$("#city").html('<option value="0" selected="selected">请选择一个市</option>');
var pros = eval(data);
for (var i=0;i<pros.length;i++) {
var cityName = pros[i].name;
var cityValue = pros[i].value;
var opt = $("<option value='" + cityValue + "'>"+cityName+"</option>");
$("#city").append(opt);
}
});
});
$("#city").change(function() {
$("#tip").append("<span>请求Ajax获取县...<br></span>");
if ($("#city").val() == '0') {
$("#county").html('');
$("#town").html('');
return;
}
$.get("ajax.do",
{type:'2',
value:$("#city").val(),
time:new Date()
},function(data) {
$("#tip").append("<span>"+$("#city").val()+"下县的信息获取成功<br></span>");
$("#county").html('<option value="0" selected="selected"皮纤>请选择一个县</option>');
var pros = eval(data);
for (var i=0;i<pros.length;i++) {
var countyName = pros[i].name;
var countyValue = pros[i].value;
var opt = $("<option value='" + countyValue + "'>"+countyName+"</option>");
$("#county").append(opt);
}
});
});
$("#county").change(function() {
$("#tip").append("<span>请求Ajax获取镇...<br></span>");
if ($("#county").val() == '0') {
$("#town").html('');
return;
}
$.get("ajax.do",
{type:'3',
value:$("#county").val(),
time:new Date()
},function(data) {
$("#tip").append("<span>"+$("#county").val()+"下镇的信息获取成功<br></span>");
$("#town").html('');
var pros = eval(data);
for (var i=0;i<pros.length;i++) {
var townName = pros[i].name;
var townValue = pros[i].value;
var opt = $("<option value='" + townValue + "'>"+townName+"</option>");
$("#town").append(opt);
}
});
});
});
</script>
</head>
<body>
省：<select id="province">
<option value="0" selected="selected">请选择一个省</option>
<option value="hubei">
湖北</option>
</select>
市：<select id="city"></select>
县：<select id="county"></select>
镇：<select id="town"></select>
<div id="tip"></div>
</body>
</html>
package com.servlet.ajax;
import java.io.IOException;import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class AjaxServlet
*/
@WebServlet("/ajax.do")
public class AjaxServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* Default constructor.
*/
public AjaxServlet() {
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request, response);
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
String type = request.getParameter("type");
String value = request.getParameter("value");
PrintWriter pw = response.getWriter();
System.out.println(type);
if ("1".equals(type) && value != null && !"".equals(value)) { // 根据省获取市
// 这里可以从数据库获取
if ("hubei".equals(value)) {
StringBuilder citys = new StringBuilder();
citys.append("[");
citys.append("{name:'武汉',value:'hubei001'},");
citys.append("{name:'襄阳',value:'hubei002'}");
citys.append("]");
System.out.println(citys.toString());
pw.print(citys.toString());
}
}
else if ("2".equals(type) && value != null && !"".equals(value)) { // 根据省获取县
// 这里可以从数据库获取
StringBuilder countries = new StringBuilder();
if ("hubei001".equals(value)) {
countries.append("[");
countries.append("{name:'AAA县',value:'wuhan001'},");
countries.append("{name:'BBB县',value:'wuhan002'},");
countries.append("{name:'CCC县',value:'wuhan003'}");
countries.append("]");
}
else if ("hubei002".equals(value)) {
countries.append("[");
countries.append("{name:'南漳县',value:'xiangyang001'},");
countries.append("{name:'古城县',value:'xiangyang002'}");
countries.append("]");
}
System.out.println(countries.toString());
pw.print(countries.toString());
}
else if ("3".equals(type) && value != null && !"".equals(value)) {
StringBuilder towns = new StringBuilder();
if ("wuhan001".equals(value)) {
towns.append("[");
towns.append("{name:'AAA镇',value:'wuhan001'},");
towns.append("{name:'BBB镇',value:'wuhan002'},");
towns.append("{name:'CCC镇',value:'wuhan003'}");
towns.append("]");
}
else if ("wuhan002".equals(value)) {
towns.append("[");
towns.append("{name:'CCC镇',value:'wuhan001'},");
towns.append("{name:'DDD镇',value:'wuhan002'},");
towns.append("{name:'EEE镇',value:'wuhan003'}");
towns.append("]");
}
else if ("wuhan003".equals(value)) {
towns.append("[");
towns.append("{name:'FFF镇',value:'wuhan001'},");
towns.append("{name:'GGG镇',value:'wuhan002'}");
towns.append("]");
}
else if ("xiangyang001".equals(value)) {
towns.append("[");
towns.append("{name:'WWW镇',value:'wuhan001'},");
towns.append("{name:'RRR镇',value:'wuhan002'}");
towns.append("]");
}
else if ("xiangyang002".equals(value)) {
towns.append("[");
towns.append("{name:'XXX镇',value:'wuhan001'},");
towns.append("{name:'YYY镇',value:'wuhan002'}");
towns.append("]");
}
System.out.println(towns.toString());
pw.print(towns.toString());
}
}
}
返回JSON数据吧,然后用JS进行拼接字符串到Document中
建议json用来传输数据，然后在前台进行拼接显示
1、后台程序生成json数据，不用拼接直接返回
2、ajax接收数据后，调用js解析json数据，可以利用jquery.parseJSON()方法解析
3、解察郑析之悄没答后启慧得到obj对象，然后可以直接obj.name这样获取对象属性
4、用html代码拼接
示例：
var obj = jQuery.parseJSON('{"name":"John","age":"20"}');
比如拼接为表格的tr
html = "<tr><td>" + obj.name + "</td><td>" + obj.age + "</td></tr>";
建议后台！js兼容性不好！