大伙应该在开发中遇到过这种情况，就是通过下拉框选择要显示的内容。如下图所示：
在没用到ajax技术时，我们可以使用两种方法来解决，一种就是选择后再次获得下拉框的数据，和显示的数据一起反映在页面上，这是最笨的方法，因为你选择多少次，下拉框的数据就要从数据库重复读取多少次。另外一种方法就是将页面分两桢，上桢是下拉框，下桢就是要读取的内容。这样做比第一种方法进步了不少，但是分桢对页面控制又有了要求。
使用Ajax正好结合了上面两种方法的优点。
下面就来看看我们是怎样实现的，我的实现平台是Struts+Spring+Hibernate，但与Ajax交道的也就是Struts，至于你后台怎样从数据库取得数据，就要看你的具体实现了：
JSP页面：
<%@ page language="java" import="java.util.*,com.wehave.oa.labourset.model.MBm" pageEncoding="gb2312"%>
<%@ taglib uri="struts-html" prefix="html" %>
<%@ taglib uri="struts-bean" prefix="bean" %>
<%@ taglib uri="struts-logic" prefix="logic" %>
<html>
<head>
<title>借阅信息</title>
<link rel="stylesheet" type="text/css" href="../css/table.css">
<link href="../css/style.css" rel="stylesheet" type="text/css">
<script src="../css/Alai_tc.js" language="JScript"></script>
<!-- html:javascript formName="lendingCartForm" method="validate"/-->
<script Language="JavaScript">
function btn_AddFolder() 
{
if(confirm("确定要归还吗？")){
//if(document.lendingCartForm.onsubmit()){
document.forms[0].submit();
//}
}
}
var req;
var dataDiv;
var dataTable;
var dataTableBody;
function Change_Select()
{
dataTableBody=document.getElementById("lendingcartDataBody");
dataTable=document.getElementById("lendingcartData");
dataDiv=document.getElementById("popup");
var zhi=document.getElementById('tbEngineFilereadId').value;
var url="returnBlueprintPage.go?method=getLendingCart&id="+zhi;
if(zhi=="0"){
alert("请选择您要察看的信息");
return;
}else{
if(window.XMLHttpRequest)
{
req=new XMLHttpRequest();
}else if(window.ActiveXObject)
{
req=new ActiveXObject("Microsoft.XMLHTTP");
}
if(req)
{
req.open("GET",url,true);
req.onreadystatechange=callback;
req.send(null);
}
}
}
function callback()
{
if(req.readyState == 4)
{
if(req.status == 200)
{
//alert(req.responseText);
document.getElementById("results").innerHTML=req.responseText;
}else{
alert("Not able to retrieve description"+req.statusText);
}
}
}
</script>
</head>
<body class="bodycolor" topmargin="0" leftmargin="0">
<html:form action="/updateLendingcarts" onsubmit="return validate(this)">
<table width="100%" background="../images/blank.gif" border="0" cellspacing="0" cellpadding="0">
<tr><td height="7" colspan="2"></td></tr>
<tr>
<td width="45%" height="23" align="left"><strong> <img src="../images/small/page_tools_bar.gif" width="13" height="13"><span class="css3 STYLE20"> 借阅信息</span></strong></td>
<td width="55%" align="right">
<img name="aa" src="../images/xin_gh.gif" width="51" height="19" alt="" align="absmiddle" onclick='btn_AddFolder()' style="cursor:hand">
<img name="aa" src="../images/xin_gb.gif" width="51" height="19" alt="" align="absmiddle" style="cursor:hand" onclick='javascript:window.close()'>
</td>
</tr>
</table>
<table width="100%" border="1" cellpadding="0" cellspacing="0" style="border-collapse: collapse; border-top-width: 0" bordercolor="#426EB4">
<tr>
<td width="30%" class="td1_a"><span class="STYLE1">请选择借阅号</span></td>
<td width="70%">
<html:select property="tbEngineFilereadId" onchange="Change_Select()" styleClass="SmallSelect">
<html:option value="0">请选择 </html:option>
<html:options collection="idlist" property="tbEngineFilereadId" labelProperty="tbEngineFilereadId"/>
</html:select>
</td>
</tr>
</table>
<div id="results"></div>
<INPUT TYPE="hidden" name="method" value="doUpdateLendingcarts">
</html:form>
</body>
</html>页面内容看上去很多，其实关键代码并不多：
首先我们的获得下拉框的数据，并在页面上反映出来：
<html:select property="tbEngineFilereadId" onchange="Change_Select()" styleClass="SmallSelect">
<html:option value="0">请选择 </html:option>
<html:options collection="idlist" property="tbEngineFilereadId" labelProperty="tbEngineFilereadId"/>
</html:select> 当选择下拉框时，就会触动"Change_Select()"事件：
var req;
var dataDiv;
var dataTable;
var dataTableBody;
function Change_Select()
{
dataTableBody=document.getElementById("lendingcartDataBody");
dataTable=document.getElementById("lendingcartData");
dataDiv=document.getElementById("popup");
var zhi=document.getElementById('tbEngineFilereadId').value;
var url="returnBlueprintPage.go?method=getLendingCart&id="+zhi;
if(zhi=="0"){
alert("请选择您要察看的信息");
return;
}else{
if(window.XMLHttpRequest)
{
req=new XMLHttpRequest();
}else if(window.ActiveXObject)
{
req=new ActiveXObject("Microsoft.XMLHTTP");
}
if(req)
{
req.open("GET",url,true);
req.onreadystatechange=callback;
req.send(null);
}
}
}
function callback()
{
if(req.readyState == 4)
{
if(req.status == 200)
{
//alert(req.responseText);
document.getElementById("results").innerHTML=req.responseText;
}else{
alert("Not able to retrieve description"+req.statusText);
}
}
} 这个js代码也不难，关键就在于"document.getElementById("results").innerHTML=req.responseText;"
我没有用JS来拼出页面，是考虑到页面的安全性问题，所以我采取了在后台拼出页面的做法。
最后看看action是怎样实现的：
/** *//**
* 根据借阅号获得借阅信息
*/
public ActionForward getLendingCart(
ActionMapping mapping,
ActionForm form,
HttpServletRequest req,
HttpServletResponse res){
String readID=(String)req.getParameter("id");
TbEngineFileread tef=lendingCartsService.getLendingCartbyID(readID);
MYhb yhb=lendingCartsService.getBM(tef.getTbEngineFilereadJyr());
String jyrname=yhb.getMYhbXm();
String jyrbmid=yhb.getMBm().getMBmBmbh();
String jyrbmname=yhb.getMBm().getMBmMc();
MYhb yhb1=lendingCartsService.getBM(tef.getTbEngineFilereadDjr());
String djrname=yhb1.getMYhbXm();
String djrbmid=yhb1.getMBm().getMBmBmbh();
String djrbmname=yhb1.getMBm().getMBmMc();
String date=tef.getTbEngineFilereadGetTime().substring(0,11);
String redate="";
if(tef.getTbEngineFilereadEndTime()!=null){
redate=tef.getTbEngineFilereadEndTime().substring(0,11);
}
res.setContentType("text/xml;charset=GB2312");
res.setHeader("Cache-Control","no-cache");
String xml="";
xml+="<table width='100%' border='1' cellpadding='0' cellspacing='0' style='border-collapse: collapse; border-top-width: 0' bordercolor='#426EB4'>";
xml+="<tbody>";
xml+="<tr>";
xml+="<td width='20%' class='td1_a'><span class='STYLE1'>档案分类ID</span></td>";
xml+="<td width='30%'>"+"<input type='text' name='tbEngineFilereadSortId' class='smallInput' size='15' maxlength='15' value="+tef.getTbEngineFilereadSortId()+" readonly='true'>"+"</td>";
xml+="<td width='20%' class='td1_a'><span class='STYLE1'>机械设备ID</span></td>";
xml+="<td width='30%'>"+"<input type='text' name='tbEngineFilereadEgineId' class='smallInput' size='15' maxlength='15' value="+tef.getTbEngineFilereadEgineId()+" readonly='true'>"+"</td>";
xml+="</tr>";
xml+="<tr>";
xml+="<td width='20%' class='td1_a'><span class='STYLE1'>蓝图ID</span></td>";
xml+="<td width='30%'>"+"<input type='text' name='tbEngineFilereadBluePrintId' class='smallInput' size='15' maxlength='15' value="+tef.getTbEngineFilereadBluePrintId()+" readonly='true'>"+"</td>";
xml+="<td width='20%' class='td1_a'><span class='STYLE1'>备注</span></td>";
xml+="<td width='30%'>"+"<input type='text' name='tbEngineFilereadMemo' class='smallInput' size='15' maxlength='15' value="+tef.getTbEngineFilereadMemo()+" >"+"</td>";
xml+="</tr>";
xml+="<tr>";
xml+="<td width='20%' class='td1_a'><span class='STYLE1'>借阅时间</span></td>";
xml+="<td width='30%'>"+"<input type='text' name='tbEngineFilereadGetTime' class='smallInput' size='15' maxlength='15' value="+date+" readonly='true'>"+"</td>";
xml+="<td width='20%' class='td1_a'><span class='STYLE1'>归还时间</span></td>";
xml+="<td width='30%'>";
xml+="<input type='text' name='tbEngineFilereadEndTime' class='smallInput' size='15' maxlength='15' value="+redate+">";
xml+="<img src='../js/date/img.gif' id='f_trigger_c' style='cursor: pointer; border: 1px solid red;' title='Date selector' onmouseover=\"this.style.background='red';\" onmouseout=\"this.style.background=''\" />";
xml+="<script type=\"text/javascript\"> ";
xml+="Calendar.setup({ inputField : \"tbEngineFilereadEndTime\", ifFormat : \"%Y-%m-%d\", button : \"f_trigger_c\", align : \"Tl\", singleClick : \"true\" });";
xml+="</"+"script>";
xml+="</td>";
xml+="</tr>";
xml+="<tr>";
xml+="<td width='20%' class='td1_a'><span class='STYLE1'>借阅人</span></td>";
xml+="<td width='30%'>"+"<input type='hidden' name='tbEngineFilereadJyr' value="+tef.getTbEngineFilereadJyr()+" >";
xml+="<input type='text' name='tbEngineFilereadJyrmc' class='smallInput' size='15' maxlength='15' value="+jyrname+" readonly='true'>"+"</td>";
xml+="<td width='20%' class='td1_a'><span class='STYLE1'>借阅人部门</span></td>";
xml+="<td width='30%'>"+"<input type='hidden' name='tbEngineFilereadJyrbm' value="+jyrbmid+" >";
xml+="<input type='text' name='tbEngineFilereadJyrbmmc' class='smallInput' size='15' maxlength='15' value="+jyrbmname+" readonly='true'>"+"</td>";
xml+="</tr>";
xml+="<tr>";
xml+="<td width='20%' class='td1_a'><span class='STYLE1'>登记人</span></td>";
xml+="<td width='30%'>"+"<input type='hidden' name='tbEngineFilereadDjr' value="+tef.getTbEngineFilereadDjr()+" >";
xml+="<input type='text' name='tbEngineFilereadDjrmc' class='smallInput' size='15' maxlength='15' value="+djrname+" readonly='true'>"+"</td>";
xml+="<td width='20%' class='td1_a'><span class='STYLE1'>登记人部门</span></td>";
xml+="<td width='30%'>"+"<input type='hidden' name='tbEngineFilereadDjrbm' value="+djrbmid+" >";
xml+="<input type='text' name='tbEngineFilereadDjrbmmc' class='smallInput' size='15' maxlength='15' value="+djrbmname+" readonly='true'>"+"</td>";
xml+="</tr>";
xml+="</tbody>";
xml+="</table>";
try {
res.getWriter().write(xml);
} catch (IOException e) {
// TODO 自动生成 catch 块
e.printStackTrace();
}
return null;
} 这段代码虽然长，但不难。
至此，从下拉框选取内容的示例就完成了。
posted on 2006-08-08 13:28
千山鸟飞绝 阅读(10888)
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Ajax