限制打开的标签数量 [英] Restriction on number of opened tabs
问题描述
网页上有一些链接。
点击右键，可以选择在新标签页中打开链接（浏览器选项）。
On right click there is option of 'open link in new tab'(browser option).
我想限制用户不要打开两个标签？
我该怎么做？
I want to restrict user for not opening more that two tabs? How can i do this?
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<ul>
<li><a href="http://localhost:8080/struts_tab/abcForm1.action" oncontextmenu="return false;"><span>First Click[Right Click disabled]</span></a></li>
<li><a href="http://localhost:8080/struts_tab/defForm2.action"><span>Second clieck[Not more than 2 tabs]</span></a></li>
</ul>
</body>
</html>
推荐答案
您不能从限制用户打开一个新选项卡。
（这让我想起没有按钮，没有地址栏，但仍然响应退格和其他事件的旧弹出窗口）
You can't restrict the user from opening a new tab.
(This reminds me the old pop-ups with no buttons, no address bar, but still responding to backspace and other events)
然而，您可以让您的应用识别打开第三个标签的尝试，并加载不同的结果，例如错误消息，例如：
You can however make your app recognize the attempt of opening a third tab, and load a different result like an error message, for example:
达到最大打开标签限制。请同时使用不超过两个选项卡。 关闭此标签
为此，您可以使用 HTML5 sessionStorage 。
注意：网络存储（ sessionStorage 和 localStorage ）。
To do this, you can use HTML5 sessionStorage.
Note: Web Storage (sessionStorage and localStorage) is supported on every browser nowadays.
sessionStorage
这是一个全局对象（
sessionStorage）维护一个在页面会话期间可用的存储区域
。只要浏览器处于打开状态，页面会话
就会持续，并且会在页面
重新加载和恢复后继续存在。 在新标签页或新窗口中打开页面将导致
a新会话启动。
sessionStorage
This is a global object (
sessionStorage) that maintains a storage area that's available for the duration of the page session. A page session lasts for as long as the browser is open and survives over page reloads and restores. Opening a page in a new tab or window will cause a new session to be initiated.
然后你可以
-
如果在sessionStorage中不存在，在JSP中生成一个唯一的令牌，并把它放在sessionStorage中，
if not present in sessionStorage, generate an unique token in JSP, and put it in sessionStorage,
$(function(){
// Read the ID. If it's null, this is a new tab:
// generate the ID and store it for later.
var tabId = sessionStorage.getItem("tabId");
if (tabId == null){
tabId = Math.random();
sessionStorage.putItem("tabId",tabId);
}
将其发回行动
send it back to the action
// Add the ID to the form (as hidden field),
// so it will be posted back in next submission.
$('<input>').attr('type' , 'hidden')
.attr('name' , 'tabId')
.attr('value' , tabId)
.appendTo('form');
});
，可能是BaseAction中的setter，其他操作的extendend，以及<$ c读取$ c> prepare（），或在拦截器中好多了;
, maybe to a setter in a BaseAction, extendend by the other actions, and read by prepare(), or much better in an Interceptor;
将它放入集合检查它不包含两个元素，否则返回错误结果，应该全局映射：
put it in a collection checking that it doesn't contain already two elements, otherwise return the error result, that should be mapped globally:
public String intercept(ActionInvocation actionInvocation) throws Exception {
Action action = (Action) actionInvocation.getAction();
if(action instanceof LimitedTabsAware){ //interface to identify special actions
ActionContext context = actionInvocation.getInvocationContext();
Map<String, String[]> request = ((HttpServletRequest)
context.get(StrutsStatics.HTTP_REQUEST)).getParameterMap();
if (request.containsKey("tabId")){
String tabId = (String) request.get("tabId")[0];
List<String> openTabs = context.getSession().get("OPEN_TABS_KEY");
if (openTabs.contains(tabId)){
return actionInvocation.invoke();
} else if (openTabs.size()>=2){
return "tabLimitExceeded"; // global result
} else {
openTabs.add(tabId);
context.getSession().put("OPEN_TABS_KEY", openTabs);
return actionInvocation.invoke();
}
} else {
throw new IllegalArgumentException("There is no tabId in this request.");
}
} else {
return actionInvocation.invoke();
}
}
然后你应该找到一种方法来识别标签何时关闭（释放一个广告位），或者：
Then you should find a way to recognize when a tab get closed (to free one slot), by either:
- 优化集合中元素的有效期（如果您暂时不使用标签，则会话过期，等等必须在集合中执行令牌）
- 否则，放置 javascript AJAX计时器在您的页面中（例如，每30秒），将
keep-alive信号发送到动作以刷新元素的有效性。如果标签关闭，则不再发送信号。
- timizing the period of validity of the elements in your collection (if you don't use a tab for some time, the session expires, and so must do the token in the collection)
- otherwise, putting a javascript AJAX timer in your page (eg. every 30 seconds), that send a
keep-alivesignal to an action to refresh the validity of the element. If the tab get closed, the signal is not sent anymore.
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