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Using AJAX to implement user name detection (JavaScript method)

Source: Internet
Author: User
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1<%@ page language= "java" contenttype= "text/html; Charset=utf-8 "2pageencoding= "UTF-8"%>3<! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 transitional//en" "HTTP://WWW.W3.ORG/TR/HTML4/LOOSE.DTD" >456<meta http-equiv= "Content-type" content= "text/html; Charset=utf-8 ">7<title>insert title here</title>89<script type= "Text/javascript" >Ten var req; One function Check () A { -var url = "Checkuser?uname=" + document.getElementById ("uname"). Value; -     if(window. XMLHttpRequest) the     { -req =NewXMLHttpRequest (); -     } -     Else if(window. ActiveXObject) { +req =NewActiveXObject ("Microsoft.XMLHTTP"); -     }        +Req.open ("GET", URL,true); AReq.onreadystatechange =Show; atReq.send (NULL); -Alert ("HHHH"); - } - function Show () { -     if(Req.readystate = = 4) { -         if(Req.status = = 200) { indocument.getElementById ("Info"). innerhtml=Req.responsetext; -         } to     } + } -</script> the<body> *<table> $<tr><td> username </td><td><input type= "text" id= "uname" ></td></tr>Panax Notoginseng<tr><td><input type= "button" onclick= "Check ()" value= "Detect user" ></td><td><div id= " Info "></div> </td></tr> -</table> the</body> +
1  PackageJavastudy;2 3 Importjava.io.IOException;4 Importjavax.servlet.ServletException;5 ImportJavax.servlet.annotation.WebServlet;6 ImportJavax.servlet.http.HttpServlet;7 Importjavax.servlet.http.HttpServletRequest;8 ImportJavax.servlet.http.HttpServletResponse;9 Ten /** One * Servlet Implementation class CheckUser A  */ -@WebServlet ("/checkuser") -  Public classCheckUserextendsHttpServlet { the     Private Static Final LongSerialversionuid = 1L; -         -     /** -      * @seeHttpservlet#httpservlet () +      */ -      PublicCheckUser () { +         Super(); A         //TODO auto-generated Constructor stub at     } -  -     /** -      * @seeHttpservlet#doget (httpservletrequest request, httpservletresponse response) -      */ -     protected voidDoget (HttpServletRequest request, httpservletresponse response)throwsservletexception, IOException { in         //TODO auto-generated Method Stub -String uname=request.getparameter ("uname"); toString[] names={"Zhang", "Yang", "Wang"}; +         Booleanflag=true; -          for(intI =0;i<names.length;i++) the         { *             if(Names[i].equals (uname)) $             {Panax Notoginsengflag=false; -                  Break; the             } +              A         } theResponse.setcharacterencoding ("Utf-8"); +         if(flag==false) -         { $Response.getwriter (). println ("The user name is registered!!!"); $         } -         Else -         { theResponse.getwriter (). println ("Registered success!!! "); -         }Wuyi //response.getwriter (). Append ("Served at:"). Append (Request.getcontextpath ()); the     } -  Wu     /** -      * @seeHttpservlet#dopost (httpservletrequest request, httpservletresponse response) About      */ $     protected voidDoPost (HttpServletRequest request, httpservletresponse response)throwsservletexception, IOException { -         //TODO auto-generated Method Stub - doget (request, response); -     } A  +}
Using AJAX to implement user name detection (JavaScript method)

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