//后台Java servlet中将从数据库中数据封装成XML
PrintWriter out = response.getWriter();
response.setContentType("text/xml;charset=GBK"

;
response.setHeader("Cache-Control", "no-cache"

;
out.println("<response>"

;
Iterator iter = allRoom.iterator();
while (iter.hasNext()) {
name = (String) iter.next();
out.println("<room>" + name + "</room>"

;
}
// 获取信息
BookinfoT info = (BookinfoT) bookInfo.get(0);
SimpleDateFormat sdf = new SimpleDateFormat("HH:mm"

;
for (int i = 0; i < bookInfo.size(); i++) {
out.println("<time>" + sdf.format(info.getBkStarttime())
+"-"+sdf.format(info.getBkEndtime())+ "</time"

;
out.println("<purpose>" + info.getBkPurpose() + "</purpose>"

;
}
// 获取上午会议室
iter = amUnuseroom.iterator();
while (iter.hasNext()) {
name = (String) iter.next();
out.println("<amUnusedRoom>" + name + "</amUnusedRoom>"

;
}
iter = pmUnuserroom.iterator();
// 获取下午会议室
while (iter.hasNext()) {
name = (String) iter.next();
out.println("<pmUnusedRoom>" + name + "</pmUnusedRoom>"

;
}
out.println("</response>"

;
allRoom = null;
bookInfo = null;
amUnuseroom = null;
pmUnuserroom = null;
service = null;
out.close();
//前台接收代码
var length=XMLData.getElementsByTagName("time").length;
length=xmlHttp.responseXML.getElementsByTagName("amUnusedRoom").length;
length=xmlHttp.responseXML.getElementsByTagName("pmUnusedRoom").length;
//请问为什么三个length的值都为0?