Javaweb StageAjax have you used it before? A brief introduction to Ajax = Asynchronous JavaScript and XML. AJAX is a technique for creating fast, Dynamic Web pages. AJAX enables Web pages to be updated asynchronously by exchanging small amounts of data in the background with the server. This means that you can update a part of a webpage without reloading the entire page. Traditional Web pages (without AJAX) if you need to update the content, you must reload the entire page surface. There are many examples of applications that use AJAX: Sina Weibo, Google maps, happy net, and more. Can ajax do asynchronous requests? You can. Ajax requests are asynchronous by default. If you want to synchronize async to False, the default is true if it is Jquery $.ajax ({url: some.php, Async: false,success : function () {}}), if it is a native Jsxmlhttp.open ("POST", Url,false); A website If there are a large number of people landing access. Then there will be a lot of sessions, if you are the programmer what to do. The session is saved in memory by default, memory resource is precious, the session data volume is high, the memory utilization is higher, the following scheme solves the session memory storage problem: 1, can set the session timeout time, reached the time-out session automatically empty < Session-config><session-timeout>20</session-timeout></session-config>2, Serialize data from session to hard disk 3, do not use session, using cookies (this method has a security problem) jsp What are the built-in objects? What are the roles? Page,pagecontext,request,response,session,application,out,config, Exceptionpage refers to a reference to an object that the JSP is translated into a servlet. The PageContext object can be used to obtain the other 8 built-in objects, and can also be used as a domain-scoped object for the JSP. The value stored in PageContext is the current page's scope of action The request represents the requested object, which can be used to obtain information about the client or to use as a domain object, and the data saved with the request is valid for the requested scope. The session represents a conversation that can be used to save the user's private information, which can also be used as a domain object, the data saved with session is valid at a session scope application: Represents the entire application scope, and the data saved using this object is valid throughout the Web application. Response is a response object that represents the response data from the server to the browser. Out:jspwriter is an object that is used to output content to a page: refers to the object that ServletConfig uses to obtain the configuration of the servlet after the JSP is translated into a servlet. Exception: Set iserrorpage= in the page " True ", ready to use, is a reference to the Throwable. The error message used to get the page. What is a cookie? What is the difference between a session and a cookie? A cookie is a session technology that saves a user's information to a browser object. Sessions are also session technology that saves session information to the server's object. Session is cookie-based use of cookies to write back to the browser jsessionid.
Java Basic Concept collection
