Ajax writing User Registration examples and technical summary (2)

Ajax| User Registration

After using JavaScript to create a XMLHttpRequest class to send an HTTP request to the server , decide what to do when you receive a response from the server . this tells the HTTP request object which JavaScript function to use to handle the response . you can set the object's onReadyStateChange property to the function name of the JavaScript you want to use, as follows: Xmlhttp_request.onreadystatechange =functionname;

FunctionName is a function name created with JavaScript, be careful not to write functionname (), and of course we can create JavaScript code directly after onReadyStateChange .

We call Request.open ()-It opens the socket channel with the server , uses an HTTP verb (GET or post) as the first parameter and takes the URL of the data provider as the second parameter Request.open () The last parameter is set to true-it indicates the asynchronous nature of the request . Note that the request has not been submitted yet . with the invocation of Request.send (), the commit is initiated-this can provide any necessary payload for post . when using asynchronous requests, we must use the Request.onreadystatechanged property to allocate the requested callback function . (if the request is synchronized, we should be able to process the result immediately after calling Request.send, but we can also block the user until the request is complete .) )
Then look at the data provider's Url,url = "/chkuserandcom", the servlet is as follows:

1/**//* 2 * Created on 2005-12-31 3 * 4 * TODO To change the template of this generated file go 5 * Window-preferences-java-code Style-code Templates 6 */ 7package com.event; 8 9import javax.servlet.ServletException; 10import javax.servlet.http.HttpServletRequest; 11import Javax.servlet.http.HttpServletResponse; 12 13import Com.beans.EBaseInfo; 14 15/** *//** * @author Alpha 2005-12-31 17 * * <p> Ajax Demo---Enterprise registration check enterprise user name and enterprise name </P> 19 * * TODO to change the template for this generated type comment go * Window-preferences-java-code Style-code Templates 22 */ 23public class Checkuserandcomnm { Private String msgstr = ""; protected void doget (HttpServletRequest request,httpservletresponse response) Num throws Servletexception 27 { 28 Ecombaseinfo info=new ecombaseinfo (); String oprate=request.getparameter ("Oprate")). Trim (); To String username=request.getparameter ("UserName"); Password=request.getparameter String ("PassWord"); Comname=request.getparameter String ("Comname"); 34 Try 36 { Panax Notoginseng if (oprate.equals ("Chkuser")) 38 { Response.setcontenttype ("text/html;charset=gb2312"); if (Username.length () <5| | Username.length () >20) 41 { Msgstr = "Sorry, the username must be a letter, number or underscore, length is 5-20 characters!"; 43} Or else 45 { A Boolean btmp=info.finduser (UserName); Look forDatabaseThere is no such user name in if (btmp) Msgstr = "Sorry, this username already exists, please change user name registration!"; Or else Msgstr = ""; 51} Response.getwriter (). write (MSGSTR); 53} "Else If" (Oprate.equals ("chkcom")) 55 { Response.setcontenttype ("text/html;charset=gb2312"); if (Comname.length () <6| | Comname.length () >100) 58 { Msgstr = "Sorry, the company name length is 6-100 characters (not including the word characters space)!"; 60} Or else 62 { A Boolean btmp=info.findcom (Comname); Look forDatabaseIs there any business name in the if (btmp) Msgstr = "Sorry, this enterprise name already exists, please change the Enterprise name registration!"; Or else Msgstr = ""; 68} Response.getwriter (). write (MSGSTR); 70 71} 72} catch (Exception ex) 74 { 75} and finally 77 { Request.setattribute ("url", url); 79} 80} 81 protected void DoPost (HttpServletRequest request,httpservletresponse response) Throws Servletexception 84 { Doget (Request,response); 86} 87} 88

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