ajax--An example of whether a user name exists asynchronously

Last Update:2017-02-28 Source: Internet

Author: User

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When you register a user on any Web site, you will check to see if the user already exists. A long time ago the process was to submit all the data to the server side for verification, obviously the user experience in this way is very bad; then with Ajax, with asynchronous interaction, when the user loses the user name to fill out other information, Ajax sends the information to the server to check if the username has been registered, This way, if the user name already exists, you can give a hint without waiting for the user to submit all the data. This approach greatly improves the user experience.
regist.jsp

Copy Code code as follows:

<%@ 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>

<script type= "Text/javascript" >

var xmlHttp;

//Create Ajax core Objects XMLHttpRequest

function Createxmlhttp () {

if (window. XMLHttpRequest) {

xmlHttp = new XMLHttpRequest ();

}else{

xmlHttp = new ActiveXObject ("Microsoft.XMLHTTP");

}

}

function Checkusername (username) {

createxmlhttp ();

//sets the request to get, sets the URL for the request, and sets it to be submitted asynchronously

Xmlhttp.open ("Get", "checkservlet?username=" +username,true);

//Copy the method address to the onReadyStateChange attribute

//Similar to phone number

Xmlhttp.onreadystatechange = Checkusernamecallback ();

//Send setup information to Ajax engine

xmlhttp.send (NULL);

}

function Checkusernamecallback () {

//ajax engine status for Success

if (xmlhttp.readystate = = 4) {

//http protocol status is successful

if (xmlhttp.status = = 200) {

var text = Xmlhttp.responsetext;

if (Text = = "true") {

document.getElementById ("msg"). InnerHTML = "This user name already exists and cannot be used!" ";

}else{

document.getElementById ("msg"). InnerHTML = "This user name can be used";

}

}

}

}

</script>

</head>

<body>

<form action= "regist.jsp" method= "POST" >

Username: <input type= "text" name= "username" onblur= "checkusername (this.value)" ><span id= "MSG" ></span ><br/>

Password: <input type= "password" name= "password" ><br/>

<input type= "Submit" value= "registered" >

<input type= "reset" value= "reset" >

</form>

</body>

</html>

Checkservlet.java

Copy Code code as follows:

public class Checkservlet extends HttpServlet {
private static final long serialversionuid = 1L;
public static final String dbdriver = "Com.microsoft.sqlserver.jdbc.SQLServerDriver";
public static final String Dburl = "Jdbc:sqlserver://localhost:1433;databasename=bbs";
public static final String dbuser = "sa";
public static final String dbpass = ' pass ';

Public Checkservlet () {
Super ();
}
protected void doget (HttpServletRequest request, httpservletresponse response) throws Servletexception, Ioexc eption {
This.dopost (request, response);
}
protected void DoPost (HttpServletRequest request, httpservletresponse response) throws Servletexception, Ioex ception {
request.setcharacterencoding ("UTF-8");
Response.setcontenttype ("text/html");
Connection conn = null;
PreparedStatement PST = NULL;
ResultSet rs = null;
PrintWriter out = Response.getwriter ();
String username = request.getparameter("Usernaem");
try{
Class.forName (dbdriver);
conn = drivermanager.getconnection (Dburl,dbuser,dbpass);
String sql = "SELECT COUNT (username) from user where username=?";
PST = conn.preparestatement (SQL);
Pst.setstring (1,username);
rs = Pst.executequery ();
if (Rs.next ()) {
if (rs.getint (1) >0) {//user name already exists
Out.print ("true");
}else{
Out.print ("false");
}

}
}catch (Exception e) {
E.printstacktrace ();
}finally{
try{
Conn.close ();
}catch (Exception e) {
E.printstacktrace ();
}
}
}
}

This article is an English version of an article which is originally in the Chinese language on aliyun.com and is provided for information purposes only. This website makes no representation or warranty of any kind, either expressed or implied, as to the accuracy, completeness ownership or reliability of the article or any translations thereof. If you have any concerns or complaints relating to the article, please send an email, providing a detailed description of the concern or complaint, to info-contact@alibabacloud.com. A staff member will contact you within 5 working days. Once verified, infringing content will be removed immediately.

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ajax--An example of whether a user name exists asynchronously

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