// Set the request method to get, set the request URL to asynchronous submission
XmlHttp. open ("GET", "CheckServlet? Username = "+ username, true );
// Copy the method address to the onreadystatechange attribute
// Similar to a phone number
XmlHttp. onreadystatechange = checkUsernameCallback ();
// Send the setting information to the Ajax Engine
XmlHttp. send (null );
}
Function checkUsernameCallback (){
// The Ajax engine status is successful.
If (xmlHttp. readyState = 4 ){
// The 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 = "register">
<Input type = "reset" value = "reset">
</Form>
</Body>
</Html>
CheckServlet. javaCopy codeThe Code is 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, IOException {
This. doPost (request, response );
}
Protected void doPost (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
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.exe cuteQuery ();
If (rs. next ()){
If (rs. getInt (1)> 0) {// the 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 ();
}
}
}
}
Start building with 50+ products and up to 12 months usage for Elastic Compute Service
1 on 1 presale consultation
24/7 Technical Support 6 Free Tickets per Quarter Faster Response
Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.
A comprehensive suite of global cloud computing services to power your business
Payment Methods We Support
