Struts+Ajax实现定时刷新Table内容，实现在线人员显示

本文链接：https://blog.youkuaiyun.com/snowsalt/article/details/1943979

Ajax代码如下：

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

<tr>

</td>

</tr>

<tr>

</tr>

<tr>

</tr>

<tr>

</tr>

<tr>

</tr>

<tr>

退出</strong>

</td>

</tr>

<tr>

</td>

</tr>

<tr>

<tr>

</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());

}