Ajax JS uses ajax to check whether the user name exists

JSP page: JS Code

1. <SCRIPT type = "text/JavaScript" Language = "JavaScript">
2. VaR XMLHTTP = false;
3. Try {
4. XMLHTTP = new activexobject ("msxml2.xmlhttp ");
5. } Catch (e ){
6. Try {
7. XMLHTTP = new activexobject ("Microsoft. XMLHTTP ");
8. } Catch (E2 ){
9. XMLHTTP = false;
10. }
11. }
12. If (! XMLHTTP & typeof XMLHttpRequest! = 'Undefined '){
13. XMLHTTP = new XMLHttpRequest ();
14. }
16. // Check whether the user name exists
17. Function callservercheckuname (){
18. // Use the get method to encapsulate the request in the URL
    
19. VaR uname = Document. getelementbyid ("u_name"). value;
20. XMLHTTP. Open ("Post", 'checkuname? U_name = '+ uname );
21. // Set the Server Response Handling Method
22. XMLHTTP. onreadystatechange = updatepagecheckuname;
23. // Send the request
24. XMLHTTP. Send (null );
25. }
26. Function updatepagecheckuname (){
27. If (XMLHTTP. readystate = 4 ){
28. VaR response = XMLHTTP. responsetext;
29. If (Response> = 1 ){
30. Alert ("the user name already exists! ");
31. } Else {
32. Alert ("registrable! ");
33. }
34. }
35. }
36. </SCRIPT>

<SCRIPT type = "text/JavaScript" Language = "JavaScript"> var XMLHTTP = false; try {XMLHTTP = new activexobject ("msxml2.xmlhttp");} catch (E) {try {XMLHTTP = new activexobject ("Microsoft. XMLHTTP ") ;}catch (E2) {XMLHTTP = false ;}} if (! XMLHTTP & typeof XMLHttpRequest! = 'Undefined') {XMLHTTP = new XMLHttpRequest ();} // checks whether the user name has a function callservercheckuname () {// request by using the get method, encapsulate the request in the URL var uname = document. getelementbyid ("u_name "). value; XMLHTTP. open ("Post", 'checkuname? U_name = '+ uname); // sets the Server Response Processing Method XMLHTTP. onreadystatechange = updatepagecheckuname; // send the XMLHTTP request. send (null);} function updatepagecheckuname () {If (XMLHTTP. readystate = 4) {var response = XMLHTTP. responsetext; If (Response> = 1) {alert ("the user name already exists! ");} Else {alert (" registrable! ") ;}}</SCRIPT>

Web. xml configuration file: XML Code

1. <Servlet>
2. <Servlet-Name>Checkuname</Servlet-Name>
3. <Servlet-class>Servlet. ajaxcheckuname</Servlet-class>
4. </Servlet>
5. <Servlet-mapping>
6. <Servlet-Name>Checkuname</Servlet-Name>
7. <URL-pattern>/Checkuname</Url-pattern>
8. </Servlet-mapping>

<Servlet> <servlet-Name> checkuname </servlet-Name> <servlet-class> servlet. ajaxcheckuname </servlet-class> </servlet> <servlet-mapping> <servlet-Name> checkuname </servlet-Name> <URL-pattern>/checkuname </url-Pattern> </servlet-mapping>

Servlet page: Java code

1. Public void dopost (httpservletrequest request, httpservletresponse response)
2. Throws servletexception, ioexception {
3. Response. setcontenttype ("text/html; charset = gb2312 ");
4. Printwriter out = response. getwriter ();
5. Try {
6. String uname = request. getparameter ("u_name ");
7. Registdaoimpl regdao = new registdaoimpl ();
8. Out. Print (regdao. checkuname (uname ));
9. } Catch (exception e ){
10. }
11. Out. Flush ();
12. Out. Close ();
13. }

Public void dopost (httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {response. setcontenttype ("text/html; charset = gb2312"); printwriter out = response. getwriter (); try {string uname = request. getparameter ("u_name"); registdaoimpl regdao = new registdaoimpl (); out. print (regdao. checkuname (uname);} catch (exception e) {} Out. flush (); out. close ();}

DAO implementation class: Java code

1. Public int checkuname (string uname ){
2. Connection conn = NULL;
3. Preparedstatement PSTM = NULL;
4. Resultset rs = NULL;
5. Int success = 0;
6. String SQL = "select u_name from u_info where u_name = '" + uname + "' or u_mobtel = '" + uname + "' or u_email = '" + uname + "'";
   
7. Try {
8. Conn = getconnection ();
9. PSTM = conn. preparestatement (SQL );
10. Rs = p0000.exe cutequery (SQL );
11. If (Rs. Next ()){
12. Success = 1;
13. }
14. Return success;
15. } Catch (exception e ){
16. E. printstacktrace ();
17. } Finally {
18. Try {
19. Conn. Close ();
20. } Catch (exception e ){
21. E. printstacktrace ();
22. }
23. }
24. Return success;
25. }