练习: 省市联动(Ajax)
// 示例一:
china.xml (位于 src 目录下)
<?xml version="1.0" encoding="utf-8"?>
<china>
<province name="北京">
<city>东城区</city>
<city>西城区</city>
<city>宣武区</city>
<city>大兴区</city>
</province>
<province name="天津">
<city>河东区</city>
<city>河西区</city>
<city>南开区</city>
<city>大港区</city>
</province>
</china>
// Servlet
// ProvinceServlet
public class ProvinceSerlvet extends HttpServlet{
public void doGet(HttpServletRequest request,HttpServletResponse response)
throws ServletException, IOException{
// 处理编码问题
response.setContentType("text/html;charset=utf-8");
try{
// 解析 xml 文档
XMLReader reader = new XMLReader();
// 获取 xml 文档的输入流
InputStream input = this.getClass().getResourceAsStream("/china.xml");
Document doc = reader.read(input);
// 使用 XPath ,获取文档中 province 元素
List<Attribute> attrList = doc.selectNodes("//province/@name");
// 遍历集合,获取 province 元素中 name 属性的值
// 并保存到 StringBuilder 中
StringBuilder sb = new StringBuilder();
for(int i=0; i<attrList.size(); i++){
sb.append(attrList.get(i).getValue());
if(i < arrList.size() - 1){
sb.append(",");
}
}
// 响应
response.getWriter().print(sb);
}catch(Exception e){
throw new RuntimeException(e);
}
}
}
// CityServlet
public class CityServlet extends HttpServlet{
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException{
request.setCharacterEncoding("utf-8");
response.setContentType("text/xml;charset=utf-8");
try{
// 解析 xml
SAXReader reader = new SAXReader();
InputStream input = this.getClass().getResourceAsStream("/china.xml");
Document doc = reader.read(input);
// 获取请求参数
String pname = request.getParameter("pname");
// XPath 查询
Element ele = doc.selectSingleNode("//province/[@name='"+pname+"']");
// 把元素转换成字符串, org.dom4j.Node
String xmlStr = ele.asXML();
// 响应给客户端
response.getWriter().print(xmlStr);
} catch(Exception e){
throw new RuntimeException(e);
}
}
}
// index.jsp
<head>
<script type="text/javascript">
// 创建 XMLHttpRequest 对象, 处理浏览器差异
function createXMLHttpRequest(){
try{
return new XMLHttpRequest();
} catch(e){
try{
return new ActiveXObject("Msxml2.XMLHTTP");
}catch(e){
try{
return new ActiveXObject("Microsoft.XMLHTTP");
}catch(e){
throw e;
}
}
}
}
// 注册监听器
window.onload = function(){
// ajax 四步,请求 ProvinceServlet, 得到所有省份的名称
// 使用每个省份的名称创建一个 <option> 元素, 添加到 <select name="province"> 中
var xmlHttp = createXMLHttpRequest();
xmlHttp.open("GET","<c:url value='/ProvinceServlet'/>",true);
xmlHttp.send(null);
xmlHttp.onreadystatechange = function(){
if(xmlHttp.readyState == 4 && xmlHttp.status == 200){
var text = xmlHttp.responseText;
// 将字符串转换成数组
var arr = text.split(",");
for(var i=0, i<arr.length; i++){
// 创建 option 元素, 示例<option value="北京">北京</option>
var op = document.creatElement("option");
op.value = arr[i];
var textNode = document.createTextNode(arr[i]);
op.appendChild(textNode);
document.getElementById("p").appendChild(op);
}
}
};
// 给 <select name="province"> 添加改变监听器
// 使用选择的省份名称请求 CityServlet, 得到 <province> 元素(xml元素)!!!
// 获取 <province> 元素中所有的 city 元素, 遍历之! 获取每个 <city> 的文本内容, 即市名称
// 使用每个市名称创建 <option> 元素添加到 <select name="city">
var ele = document.getElementById("p");
ele.onchange = function(){
var xmlHttp = createXMLHttpRequest();
xmlHttp.open("POST","<c:url value='/CityServlet'/>",true);
xmlHttp.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
xmlHttp.send("pname="+this.value);
xmlHttp.onreadystatechange = function(){
if(xmlHttp.readyState == 4 && xmlHttp.status == 200){
// 清空 <option name="city"> 原有的内容
var citySelect = document.getElementById("c");
var optionEleList = citySelect.getElementsByTagName("option");
while(optionEleList.length > 1){
citySelect.removeChild(optionEleList[i]);
}
var doc = xmlHttp.responseXML;
// 获取所有的 city 元素
var cityEleList = doc.getElementsByTagName("city");
for(var i=0; i<cityEleList.length; i++){
var cityEle = cityEleList[i];
var cityName;
// 处理浏览器差异
if(window.addEventListener){
cityName = cityEle.textContent;
} else {
cityName = cityEle.text;
}
// 添加到 <select name="city"> 元素中
var op = document.createElement("op");
op.value = cityName;
var textNode = document.createTextNode(cityName);
op.appendChild(textNode);
citySelect.appendChild(op);
}
}
};
};
};
</script>
</head>
<body>
<h1>省市联动</h1>
<select name="province" id="p">
<option>===请选择省===</option>
</select>
<select name="city" id="c">
<option>===请选择市===</option>
</select>
</body>
// 升级版, JQuery 和 Ajax
<head>
<script type="text/javascript" src="<c:url value='/jquery/jquery-3.2.1.min.js'/>"></script>
<script type="text/javascript">
$(document).ready(function(){
$.ajax({
url:"<c:url value='/ProvinceServlet'/>",
success:function(data){
var arr = data.split(",");
$.each(arr,function(index,value){
$("#pv").append($("<option value='"+value+"'>"+value+"</option>"));
});
}
});
// 在 <select name="province"> 上注册事件
$("#pv").change(function(){
$("#c").empty();
$.ajax({
url:"<c:url value='/CityServlet'/>",
data:{pname:$("#pv").val()},
type:"POST",
success:function(data){
$.each($(data).find("city"), function(key,value){
$("#c").append(
$("<option value='"+value.textContent+"'>"+value.textContent+"</option>"
));
});
}
});
});
});
</script>
</head>
<body>
<h1>省市联动</h1>
<select name="province" id="pv">
<option>===请选择省===</option>
</select>
<select name="city" id="c">
<option>===请选择市===</option>
</select>
</body>
参考资料:
