This is a mistake I saw on the Internet Ajax I changed the correct, but can not find that post.
Verify with servlet:
Copy Code code as follows:
Package Servlet;
Import java.io.*;
Import java.sql.*;
Import java.io.IOException;
Import Java.io.PrintWriter;
Import javax.servlet.*;
Import Javax.servlet.http.HttpServletRequest;
Import Javax.servlet.http.HttpServletResponse;
Import Javax.servlet.http.HttpServlet;
public class Checkservlet extends HttpServlet {
static HttpServletRequest request = NULL;
static HttpServletResponse response = NULL;
public static void Main (string[] args) throws Exception, ioexception{
Checkservlet C = new Checkservlet ();
C.dopost (request, response);
}
public static final String dbdriver = "Com.mysql.jdbc.Driver";
public static final String Dburl = "jdbc:mysql://localhost:3306/spring";
public static final String dbuser = "root";
public static final String Dbpass = "Liangke";
public void doget (HttpServletRequest request, httpservletresponse response)
Throws Servletexception, IOException {
This.dopost (request, response);
}
public void DoPost (HttpServletRequest request, httpservletresponse response)
Throws Servletexception, IOException {
Request.setcharacterencoding ("GBK");
Response.setcontenttype ("text/html");
Connection conn = null;
PreparedStatement pstmt = null;
ResultSet rs = null;
PrintWriter out = Response.getwriter ();
String UserID = request.getparameter ("userid")//authenticated user name
try {
Class.forName (Dbdriver);
conn = Drivermanager.getconnection (Dburl, Dbuser, Dbpass);
String sql = "SELECT * from user where username=?";
pstmt = conn.preparestatement (sql);
Pstmt.setstring (1, userid);
rs = Pstmt.executequery ();
StringBuffer jsonstr=new StringBuffer ();
Jsonstr.append ("[{flag: '");
if (Rs.next ()) {
Jsonstr.append ("True", Alerttest: ' AAA '}]);
Out.println (Jsonstr.tostring ());
}else{
Jsonstr.append ("false", Alerttest: ' BBB '}]);
Out.println (Jsonstr.tostring ());
}
Out.close ();
catch (Exception e) {
E.printstacktrace ();
finally {
try {
Conn.close ();
catch (SQLException e) {
E.printstacktrace ();
}
}
}
}
Foreground Display page:
Copy Code code as follows:
<%@ page language= "java" pageencoding= "Utf-8"%>
<%@ page import= "java.sql.*"%>
<%@ page import= "java.util.*"%>
<!doctype html>
<body>
<script>
OnLoad This method is invoked when the page is loaded Initpage
Window.onload = Initpage;
function Initpage () {
Alert ("EE");
document.getElementById ("userid"). onblur = checkuserid;//Reference function method. onblur Event executes JavaScript code when the user leaves the input box
}
Create a Request object
function Createrequest () {
try {
Request = new XMLHttpRequest ();
} catch (tryms) {
try {
Request = new ActiveXObject ("Msxml2.xmlhttp");
} catch (Otherms) {
try {
Request = new ActiveXObject ("Microsoft.XMLHTTP");
} catch (Failed) {
request = NULL;
}
}
}
return request;
}
Check that the user name is duplicated
function Checkuserid () {
Alert ("DD");
Request=createrequest ();
var thename = document.getElementById ("userid"). Value;
Request.open ("POST", "checkservlet?userid=" +thename,true);
Request.onreadystatechange=checkuseridcallback;
Request.send (NULL);
document.getElementById ("msg"). Innerhtml= "Verifying ...";
}
callback function
function Checkuseridcallback () {
if (request.readystate==4) {
if (request.status==200) {
var v = request.responsetext;
var value1= eval (v) [0];
if (value1.flag== "true") {
document.getElementById ("msg"). innerhtml= "User ID repeat";
}else{
document.getElementById ("msg"). innerhtml= "This user ID can be registered";
}
}
}
}
</script>
<form action= "check.jsp" method= "POST" >
User id:
<input type= "text" id= "userid" name= "userid" >
<span id= "MSG" ></span>
<br>
Name
<input type= "text" name= "name" >
</form>
</body>
