Index. jsp
<% @ Page contenttype = "text/html; charset = GBK" %> <br/> <! Doctype HTML public "-// W3C // dtd html 4.01 transitional // en"> <br/> <HTML> <br/> <pead> <br/> <title> check.html </title> </P> <p> <meta http-equiv = "keywords" content = "keyword1, keyword2, keyword3 "> <br/> <meta http-equiv =" Description "content =" this is my page "> </P> <p> <! -- <LINK rel = "stylesheet" type = "text/CSS" href = ". /styles.css "mce_href =" styles.css "> --> </P> <p> </pead> <br/> <MCE: Script Type =" text/JavaScript "> <! -- <Br/> var http_request = false; <br/> function send_request (URL) {// initialization, specify the processing function, and send the request function <br/> http_request = false; <br/> // start to initialize the XMLHTTPRequest object <br/> If (window. XMLHttpRequest) {// Mozilla Browser <br/> http_request = new XMLHttpRequest (); <br/> If (http_request.overridemimetype) {// set the mime Category <br/> http_request.overridemimetype ('text/xml'); <br/>}< br/> else if (window. activexobject) {// IE Browser <br/> try {<br/> http_request = new activexobject ("msxml2.xmlhttp"); <br/>} catch (E) {<br/> try {<br/> http_request = new activexobject ("Microsoft. XMLHTTP "); <br/>}catch (e) {}< br/>}< br/> If (! Http_request) {// exception. An error occurred while creating the object instance. <br/> window. alert ("the XMLHTTPRequest object instance cannot be created. "); <br/> return false; <br/>}< br/> http_request.onreadystatechange = processrequest; <br/> // determine the request sending method and URL, and whether to execute the following code synchronously <br/> http_request.open ("get", URL, true ); <br/> http_request.send (null); <br/>}< br/> // function for processing returned information <br/> function processrequest () {<br/> If (http_request.readystate = 4) {// judge the object status <br/> If (http_re Quest. status = 200) {// information returned successfully. Start to process the information <br/> alert (http_request.responsetext ); <br/>} The else {// page is abnormal <br/> alert ("the page you requested has an exception. "); <Br/>}< br/> function usercheck () {<br/> var F = document. form1; <br/> var username = f. username. value; <br/> If (username = "") {<br/> window. alert ("the user name can not be null! "); <Br/> F. username. focus (); <br/> return false; <br/>}< br/> else {<br/> send_request ('check1. JSP? Username = '+ username); <br/>}</P> <p> // --> </MCE: SCRIPT> <br/> <body> <br/> <form name = "form1" Action = "" method = "Post"> <br/> User Name: <input type = "text" name = "username" value = ""> <br/> <input type = "button" name = "check" value = "check" onclick = "usercheck () "> <br/> <input type =" Submit "name =" Submit "value =" Submit "> <br/> </form> <br/> </body> <br/> </ptml> <br/> This article is from the csdn blog, reprinted please indicate the source: http://blog.csdn.net/sunrisefe/archive/2006/01/16/580474.aspx
Check1.jsp
<% @ Page contenttype = "text/html; charset = gb2312 "Language =" Java "errorpage =" "%> <br/> <% <br/> string username = request. getparameter ("username"); <br/> If ("educhina ". equals (username) <br/>{< br/> out. print ("the user name has been registered. Please change to another user name. "); <Br/>}< br/> else <br/>{< br/> out. Print (" the user name has not been used. You can continue. "); <Br/>}< br/> %>
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