Struts+Ajax实现定时刷新Table内容，实现在线人员显示收藏
在开发在线收费系统时，因为考及时显示所有在线用户，所以采用了AJAX来实现，这是我的一点体会
Ajax代码如下：
<script language="JavaScript" type="">
var XMLHttpReq = false;
//创建XMLHttpRequest对象
function createXMLHttpRequest()...{
if(window.XMLHttpRequest)...{ //Mozilla浏览器
XMLHttpReq = new XMLHttpRequest();
}
else if(window.ActiveXObject)...{ //IE浏览器
try...{
XMLHttpReq = new ActiveXObject("Msxml2.XMLHTTP");
}catch(e)...{
try...{
XMLHttpReq = new ActiveXObject("Microsoft.XMLHTTP");
}catch(e)...{}
}
}
}
//发送请求函数
function sendRequest()...{
var url="handlerList.do"
createXMLHttpRequest(); //调用创建对象方法
XMLHttpReq.open("post",url,true);
XMLHttpReq.onreadystatechange = processResponse;//指定响应函数 调用
XMLHttpReq.setRequestHeader("If-Modified-Since","0");
XMLHttpReq.send(null);//发送请求
}
//处理返回信息函数
function processResponse()...{
if(XMLHttpReq.readyState==4)...{//代表服务器已经传回所有的信息，可以处理了
if(XMLHttpReq.status==200)...{ //信息已经成功返回,开始处理信息
updateTable();
setInterval("sendRequest()",10000);
}else //页面不正常
window.alert("您所请求的页面有异常。");
}
}
//更新table的内容
function updateTable()...{
clearTable();
var results=XMLHttpReq.responseXML.getElementsByTagName("handler");
for(var i=0;i<results.length;i++)...{
var name=results[i].childNodes[0].firstChild.nodeValue;
addTableRow(name);
}
}
//向table的行添加单元格
function addTableRow(name)...{
var table=document.getElementById("handlerList");
var row = table.insertRow(1);
var cell = row.insertCell(0);
cell.align="center";
cell.innerHTML="<strong>"+name+"</strong>";
}
//清除表格内容
function clearTable()...{
var table=document.getElementById("handlerList");
for(var i=table.rows.length-1;i>0;i--)
...{
table.deleteRow(i);
}
}
</script>
下面是JSP的内容
<body onload="sendRequest()">
<table width = "124" height="100%" border="0" cellspacing="0" background="../image/bak.jpg">
<tr>
<td height="39" align="center" valign="middle"><p align="center"><html:link forward="main"><strong>业务受理</strong></html:link></p>
</td>
</tr>
<tr>
<td height="36" align="center" valign="middle"><html:link forward="payMoney"><strong>业务处理</strong></html:link></td>
</tr>
<tr>
<td height="35" align="center" valign="middle"><html:link forward="query"><strong>业务查询</strong></html:link></td>
</tr>
<tr>
<td height="35" align="center" valign="middle"><html:link forward="update"><strong>资料修改</strong></html:link></td>
</tr>
<tr>
<td height="42" align="center" valign="middle"><strong><html:link href="admin.jsp">管理</html:link></strong></td>
</tr>
<tr>
<td height="34" align="center" valign="middle"><strong><br>
退出</strong>
</td>
</tr>
<tr>
<td height="21" align="center" valign="middle">
</td>
</tr>
<tr>
<td align="center" valign="middle">
<table id="handlerList" width="100%" height="20" border="0" cellpadding="0" cellspacing="0">
<tr>
<td align="center"><strong>在线人员：</strong></td>
</tr>
</table>
</td>
</tr>
</table>
</body>
handlerListAction内容如下
public ActionForward execute(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response) ...{
try ...{
request.setCharacterEncoding("GBK");
} catch (UnsupportedEncodingException e) ...{
// TODO Auto-generated catch block
e.printStackTrace();
}
response.setContentType("text/xml;charset=GBK");
response.setHeader("Cache-Control","no-cache");
ServletContext context=getServlet().getServletContext();
List list=(List)context.getAttribute("onlineHandler");
PrintWriter out = null;
try ...{
out = response.getWriter();
} catch (IOException e) ...{
// TODO Auto-generated catch block
e.printStackTrace();
}
String str="";
str="<?xml version="1.0" encoding="GBK"?>";
str+="<handlers>";
for(int i=0;i<list.size();i++)
...{
str+="<handler>";
Handler handler=(Handler)list.get(i);
str+="<name>"+handler.getHandlerName()+"</name>";
str+="</handler>";
}
str+="</handlers>";
out.println(str);
out.close();
return null;
}
为了实现对在线人员的统计
我在登陆的时候将登陆人员放入了ServletContext中，然后使用HttpSessionListenter来监视登陆用户情况
public class SessionListenter implements HttpSessionListener ...{
public SessionListenter()
...{}
public void sessionCreated(HttpSessionEvent arg0) ...{
// TODO Auto-generated method stub
System.out.println("Session监听启动了");
arg0.getSession().setMaxInactiveInterval(1*60);//设置Session的过期时间为1分钟
}
public void sessionDestroyed(HttpSessionEvent arg0) ...{
System.out.println("session释放启动了");
HttpSession session = arg0.getSession();
ServletContext ctx = session.getServletContext();
List list = (List)ctx.getAttribute("onlineHandler");
list.remove(session.getAttribute("handler"));
System.out.println("List的个数为:"+list.size());
}
Ajax代码如下：
<script language="JavaScript" type="">
var XMLHttpReq = false;
//创建XMLHttpRequest对象
function createXMLHttpRequest()...{
if(window.XMLHttpRequest)...{ //Mozilla浏览器
XMLHttpReq = new XMLHttpRequest();
}
else if(window.ActiveXObject)...{ //IE浏览器
try...{
XMLHttpReq = new ActiveXObject("Msxml2.XMLHTTP");
}catch(e)...{
try...{
XMLHttpReq = new ActiveXObject("Microsoft.XMLHTTP");
}catch(e)...{}
}
}
}
//发送请求函数
function sendRequest()...{
var url="handlerList.do"
createXMLHttpRequest(); //调用创建对象方法
XMLHttpReq.open("post",url,true);
XMLHttpReq.onreadystatechange = processResponse;//指定响应函数 调用
XMLHttpReq.setRequestHeader("If-Modified-Since","0");
XMLHttpReq.send(null);//发送请求
}
//处理返回信息函数
function processResponse()...{
if(XMLHttpReq.readyState==4)...{//代表服务器已经传回所有的信息，可以处理了
if(XMLHttpReq.status==200)...{ //信息已经成功返回,开始处理信息
updateTable();
setInterval("sendRequest()",10000);
}else //页面不正常
window.alert("您所请求的页面有异常。");
}
}
//更新table的内容
function updateTable()...{
clearTable();
var results=XMLHttpReq.responseXML.getElementsByTagName("handler");
for(var i=0;i<results.length;i++)...{
var name=results[i].childNodes[0].firstChild.nodeValue;
addTableRow(name);
}
}
//向table的行添加单元格
function addTableRow(name)...{
var table=document.getElementById("handlerList");
var row = table.insertRow(1);
var cell = row.insertCell(0);
cell.align="center";
cell.innerHTML="<strong>"+name+"</strong>";
}
//清除表格内容
function clearTable()...{
var table=document.getElementById("handlerList");
for(var i=table.rows.length-1;i>0;i--)
...{
table.deleteRow(i);
}
}
</script>
下面是JSP的内容
<body onload="sendRequest()">
<table width = "124" height="100%" border="0" cellspacing="0" background="../image/bak.jpg">
<tr>
<td height="39" align="center" valign="middle"><p align="center"><html:link forward="main"><strong>业务受理</strong></html:link></p>
</td>
</tr>
<tr>
<td height="36" align="center" valign="middle"><html:link forward="payMoney"><strong>业务处理</strong></html:link></td>
</tr>
<tr>
<td height="35" align="center" valign="middle"><html:link forward="query"><strong>业务查询</strong></html:link></td>
</tr>
<tr>
<td height="35" align="center" valign="middle"><html:link forward="update"><strong>资料修改</strong></html:link></td>
</tr>
<tr>
<td height="42" align="center" valign="middle"><strong><html:link href="admin.jsp">管理</html:link></strong></td>
</tr>
<tr>
<td height="34" align="center" valign="middle"><strong><br>
退出</strong>
</td>
</tr>
<tr>
<td height="21" align="center" valign="middle">
</td>
</tr>
<tr>
<td align="center" valign="middle">
<table id="handlerList" width="100%" height="20" border="0" cellpadding="0" cellspacing="0">
<tr>
<td align="center"><strong>在线人员：</strong></td>
</tr>
</table>
</td>
</tr>
</table>
</body>
handlerListAction内容如下
public ActionForward execute(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response) ...{
try ...{
request.setCharacterEncoding("GBK");
} catch (UnsupportedEncodingException e) ...{
// TODO Auto-generated catch block
e.printStackTrace();
}
response.setContentType("text/xml;charset=GBK");
response.setHeader("Cache-Control","no-cache");
ServletContext context=getServlet().getServletContext();
List list=(List)context.getAttribute("onlineHandler");
PrintWriter out = null;
try ...{
out = response.getWriter();
} catch (IOException e) ...{
// TODO Auto-generated catch block
e.printStackTrace();
}
String str="";
str="<?xml version="1.0" encoding="GBK"?>";
str+="<handlers>";
for(int i=0;i<list.size();i++)
...{
str+="<handler>";
Handler handler=(Handler)list.get(i);
str+="<name>"+handler.getHandlerName()+"</name>";
str+="</handler>";
}
str+="</handlers>";
out.println(str);
out.close();
return null;
}
为了实现对在线人员的统计
我在登陆的时候将登陆人员放入了ServletContext中，然后使用HttpSessionListenter来监视登陆用户情况
public class SessionListenter implements HttpSessionListener ...{
public SessionListenter()
...{}
public void sessionCreated(HttpSessionEvent arg0) ...{
// TODO Auto-generated method stub
System.out.println("Session监听启动了");
arg0.getSession().setMaxInactiveInterval(1*60);//设置Session的过期时间为1分钟
}
public void sessionDestroyed(HttpSessionEvent arg0) ...{
System.out.println("session释放启动了");
HttpSession session = arg0.getSession();
ServletContext ctx = session.getServletContext();
List list = (List)ctx.getAttribute("onlineHandler");
list.remove(session.getAttribute("handler"));
System.out.println("List的个数为:"+list.size());
}