Check whether the username is unique (instance Code) and the AJAX application instance is used for ajax application instances.
The following code is displayed:
The following is a simple example to check whether the user name is unique (directly refer to the Code ):
Front-End Interface:
<% @ Page language = "java" contentType = "text/html; charset = GB18030" pageEncoding = "GB18030" %> <! DOCTYPE html PUBLIC "-// W3C // dtd html 4.01 Transitional // EN "" http://www.w3.org/TR/html4/loose.dtd "> <Html>AJAX file:
<Script language = "javascript"> function createRequest (url) {http_request = false; if (window. XMLHttpRequest) {// non-IE browser http_request = new XMLHttpRequest (); // create XMLHttpRequest object} else if (window. activeXObject) {// IE browser try {http_request = new ActiveXObject ("Msxml2.XMLHTTP"); // create an XMLHttpRequest object} catch (e) {try {http_request = new ActiveXObject ("Microsoft. XMLHTTP "); // create an XMLHttpRequest object} c Atch (e) {}} if (! Http_request) {alert ("You cannot create an XMLHttpRequest object instance! "); Return false;} http_request.onreadystatechange = getResult; // call the return result processing function http_request.open ('get', url, true ); // create a connection with the server: http_request.send (null); // send a request to the server} function getResult () {if (http_request.readyState = 4) {// determine the Request status if (http_request.status = 200) {// if the request is successful, process the returned result document. getElementById ("toolTip "). innerHTML = http_request.responseText; // you can specify the document content. getElementById ("toolTip "). st Yle. display = "block"; // display prompt box} else {// The request page has an error alert ("the page you requested has an error! ") ;}} Function checkUser (userName) {if (userName. value =" ") {alert (" Enter your userName! "); UserName. focus (); return;} else {createRequest ('checkuser. jsp? User = '+ userName. value) ;}</script>Jsp file:
In this example, the database is not connected, but the registered user is simply represented by an array.
<% @ Page language = "java" import = "java. util. * "pageEncoding =" GB18030 "%> <% String [] userList = {" Tomorrow technology "," mr "," mrsoft "," wgh "}; // create a one-dimensional array String user = new String (request. getParameter ("user "). getBytes ("ISO-8859-1"), "GB18030"); // get the username Arrays. sort (userList); // sorts the array int result = Arrays. binarySearch (userList, user); // search for an array if (result>-1) {out. println ("sorry, this user name has been registered! "); // Output detection result} else {out. println (" congratulations, this user name is not registered! "); // Output detection result }%>Summary
The above section describes how to check whether the user name of an AJAX application instance is unique (the instance Code). I hope it will help you. If you have any questions, please leave a message for me, the editor will reply to you in a timely manner. Thank you very much for your support for the help House website!
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