树型菜单可以说是项目中应用最为广泛的运用。以前无论使用微软控件的树型，还是比较优秀的阿赖树型，都是将数据全部读出，然后再分级显示。这样如果数据量大，那么第一次显示将需要客户等待很长一段时间，降低了客户的体验度。如今使用ajax，事情变得简单了。
此运用参考了《征服web2.0开发技术详解》的例子。
我使用的平台是struts+spring+hibernate，但与ajax打交道的也就是struts。我无法将整个代码贴出来，因此把重要的前台ajax代码贴出来，至于后台的代码就看你自己所使用的技术了。
1、jsp页面
<%
@ page language
=
"
java
"
contentType
=
"
text/html; charset=GB2312
"
import
=
"
java.util.*,com.wehave.oa.cecontract.model.TbJyhtflb
"
%>
<
html
>
<
head
>
<
title
>
Insert title here
</
title
>
<
link rel
=
"
stylesheet
"
href
=
"
../css/tree.css
"
>
<
script type
=
"
text/javascript
"
src
=
"
../js/tree_ajax.js
"
></
script
>
<
script type
=
"
text/javascript
"
src
=
"
../js/tree_htfl.js
"
></
script
>
<
script languge
=
"
javascript
"
>
function ShowDetail(ID,NAME,FLAG)
{
window.parent.right.location
=
"
getContract.go?method=doGetContract&folderID=
"
+
ID
+
"
&&folderName=
"
+
NAME
+
"
&&flag=
"
+
FLAG;
}
</
script
>
</
head
>
<
body bgcolor
=
"
#F6F9FF
"
>
<
tbody
>
<
table cellpadding
=
"
0
"
cellspacing
=
"
0
"
width
=
"
300
"
>
<
div id
=
"
load
"
style
=
"
display:none
"
>
<
img src
=
"
../images/tree_loading.gif
"
>
Loading data..
</
div
>
<
ul
class
=
"
tree
"
>
<%
List treeList
=
(List)request.getAttribute(
"
treefolder
"
);
Iterator it
=
treeList.iterator();
while
(it.hasNext())
{
out.println(it.next().toString());
}
%>
</
table
>
</
tbody
>
</
body
>
</
html
>
2、js代码
function showHide( id )
{
var el= document.getElementById( id );
var bExpand = true;
var images = el.getElementsByTagName("IMG");
if (images[0].src.indexOf("tree_minus.gif")!=-1)
{
bExpand = false;
images[0].src="../images/tree_plus.gif";
}else{
images[0].src="../images/tree_minus.gif";
}
var subs=el.lastChild;
if(bExpand)
subs.style.display="block";
else
subs.style.display="none";
}
function getSubTree( id ,submitURL)
{
var submitURL=submitURL
postXmlHttp( submitURL, 'parseSubTree("'+id+'")' ,'load("'+id+'")');
}
function parseSubTree(id)
{
var el= document.getElementById( id );
var ulElmt= document.createElement("UL");
ulElmt.innerHTML=_xmlHttpRequestObj.responseText;
el.appendChild(ulElmt);
var images = el.getElementsByTagName("IMG");
images[0].setAttribute("src", "../images/tree_minus.gif");
images[0].setAttribute("onclick", new Function("showHide('"+id+"')"));
var aTag = el.getElementsByTagName("A");
aTag[0].setAttribute("onclick", new Function("showHide('"+id+"')"));
var loadDiv= document.getElementById( "load" );
loadDiv.style.display="none";
}
function load(id)
{
var loadDiv= document.getElementById( "load" );
loadDiv.style.display="block";
}
var _postXmlHttpProcessPostChangeCallBack;
var _xmlHttpRequestObj;
var _loadingFunction;
function postXmlHttp( submitUrl, callbackFunc ,loadFunc)
{
_postXmlHttpProcessPostChangeCallBack = callbackFunc;
_loadingFunction = loadFunc;
if(window.createRequest)
{
try{
_xmlHttpRequestObj=window.createRequest();
_xmlHttpRequestObj.open('POST',submitUrl,true);
_xmlHttpRequestObj.onreadystatechange=postXmlHttpProcessPostChange;
_xmlHttpRequestObj.send();
}
catch(ee){}
}
else if(window.XMLHttpRequest)
{
_xmlHttpRequestObj=new XMLHttpRequest();
_xmlHttpRequestObj.overrideMimeType('text/xml');
_xmlHttpRequestObj.open('POST',submitUrl,true);
_xmlHttpRequestObj.onreadystatechange=postXmlHttpProcessPostChange;
_xmlHttpRequestObj.send("");
}
else if(window.ActiveXObject)
{
_xmlHttpRequestObj=new ActiveXObject("Microsoft.XMLHTTP");
_xmlHttpRequestObj.open('POST',submitUrl,true);
_xmlHttpRequestObj.onreadystatechange=postXmlHttpProcessPostChange;
_xmlHttpRequestObj.send();
}
};
function postXmlHttpProcessPostChange( )
{
if( _xmlHttpRequestObj.readyState==4)
{
if(_xmlHttpRequestObj.status==200){
setTimeout( _postXmlHttpProcessPostChangeCallBack, 2 );
}else{
alert(_xmlHttpRequestObj.status);
}
}
if ( _xmlHttpRequestObj.readyState==1 )
{
setTimeout( _loadingFunction, 2 );
}
} 3、action代码
/** *//**
* 展开第一层目录
*/
public ActionForward doGetFolderList(
ActionMapping mapping,
ActionForm form,
HttpServletRequest req,
HttpServletResponse res){
List list = treeCatalogService.getChildren("0");
List TreeFolder=new ArrayList();
Iterator it=list.iterator();
while(it.hasNext()){
TbJyhtflb htfl=(TbJyhtflb)it.next();
String s=treeCatalogService.renderTreeViewAjax(htfl);
TreeFolder.add(s);
}
req.setAttribute("treefolder",TreeFolder);
return mapping.findForward("foldertree");
}
/** *//**
* 展开下级目录
*/
public ActionForward doGetSubFolderList(
ActionMapping mapping,
ActionForm form,
HttpServletRequest req,
HttpServletResponse res){
String parentID = req.getParameter("parentID"); //获得id的值
if (parentID!=null&&!parentID.equals("")){ //如果不为null和空
res.setContentType("text/html;charset=GB2312");
List list = treeCatalogService.getChildren(parentID);
Iterator it=list.iterator();
try {
PrintWriter out= res.getWriter();
while(it.hasNext()){
TbJyhtflb htfl=(TbJyhtflb)it.next();
out.println(treeCatalogService.renderTreeViewAjax(htfl));
}
out.close();
}catch(Exception e){
e.printStackTrace();
}
}
return null;
} 4、service层代码
/** *//**
* 函数说明：展开目录
* 参数说明： 目录对象
* 返回值：展开目录的HTML代码
*/
public String renderTreeViewAjax(TbJyhtflb htfl) {
StringBuffer content = new StringBuffer();
String ID=htfl.getTbJyhtflbZlId();
String NAME=htfl.getTbJyhtflbMc();
String FLAG=htfl.getTbJyhtflbLb();
content.append("<li id='"+ID+"'>");
if (treeCatalogDAO.canExpand(ID))
content.append("<img src=../images/tree_plus.gif onClick=\"getSubTree('"+ID+"')\">");
else
content.append("<img src=../images/tree_blank.gif>");
content.append("<img src=../images/tree_folder.gif><a href=\"javascript:ShowDetail('"+ID+"','"+NAME+"','"+FLAG+"')\"");
if (treeCatalogDAO.canExpand(ID)){
String submitURL="getFolderList.go?method=doGetSubFolderList&parentID="+ID;
content.append(" onClick=\"getSubTree('"+ID+"',submitURL)\"");
}
content.append(">"+NAME+"</a>");
content.append("</li>");
return content.toString();
} 代码基本就是这样了，希望对大家有用。