AJAX用于判定用户是否注册
在很多注册的页面上，我们可能会遇到以下情况，当我们注册用户名的时候可能会提示该用户名已注册，其实现是应用AJAX技术。
首先写一个登陆页面
<html>
<head>
<title></title>
<scripttype="text/javascript">
varxmlHttp;
varflag;
functioncreateXMLHttp(){
if(window.XMLHttpRequest){
xmlHttp=newXMLHttpRequest();
}else{
xmlHttp=newActiveXObject("Microsoft.XMLHTTP");
}
}
functioncheckUserid(userid){
createXMLHttp();
xmlHttp.open("POST","CheckServlet?userid="+userid);
xmlHttp.onreadystatechange=checkUseridCallback;
xmlHttp.send();
document.getElementById("msg").innerHTML="正在验证。。。";
}
functioncheckUseridCallback(){
if(xmlHttp.readyState==400){
if(xmlHttp.status==200){
vartext=xmlHttp.responseText;
if(text=="true"){
flag=false;
document.getElementById("msg").innerHTML="用户ID重复，无法使用";
}else{
flag=true;
document.getElementById("msg").innerHTML="此用户ID可以注册";
}
}
}
}
functioncheckForm(){
returnflag;
}
</script>
</head>
<body>
<formaction="tt.jsp"method="post"onsubmit="returncheckForm()">
用户ID<inputtype="text"name="userid"onblur="checkUserid(this.value)"><spanid="msg"></span><br>
姓名：<inputtype="text"name="name"><br>
密码：<inputtype="password"name="password"><br>
<inputtype="button"value="注册">
<inputtype="reset"value="重置">
</form>
</body>
</html>
随后写一个servlet的Java代码
importjava.io.IOException;
importjava.io.PrintWriter;
importjava.sql.Connection;
importjava.sql.DriverManager;
importjava.sql.PreparedStatement;
importjava.sql.ResultSet;
importjava.sql.SQLException;
importjavax.servlet.ServletException;
importjavax.servlet.http.HttpServlet;
importjavax.servlet.http.HttpServletRequest;
importjavax.servlet.http.HttpServletResponse;
publicclassCheckServletextendsHttpServlet{
publicstaticfinalStringDBDRIVER="oracle.jdbc.OracleDriver";
publicstaticfinalStringDBURL="jdbc:oracle:thin:@59.173.240.149:1521:heer";
publicstaticfinalStringDBUSER="hnsyu_dev";
publicstaticfinalStringDBPASS="hnsyuok";
publicvoiddoGet(HttpServletRequestrequest,HttpServletResponseresponse)
throwsServletException,IOException{
this.doPost(request,response);
}
publicvoiddoPost(HttpServletRequestrequest,HttpServletResponseresponse)
throwsServletException,IOException{
request.setCharacterEncoding("gbk");
response.setContentType("text/html");
Connectionconnection=null;
PreparedStatementpreparedStatement=null;
ResultSetresultSet=null;
PrintWriterout=response.getWriter();
Stringuserid=request.getParameter("userid");
try{
Class.forName(DBDRIVER);
connection=DriverManager.getConnection(DBURL,DBUSER,DBPASS);
Stringsql="selectcount(userid)fromuserdemowhereuserid=?";
preparedStatement=connection.prepareStatement(sql);
preparedStatement.setString(1,userid);
resultSet=preparedStatement.executeQuery();
if(resultSet.next()){
if(resultSet.getInt(1)>0){
out.print("false");
System.out.println("true");
}else{
out.print("false");
}
}
out.close();
}catch(Exceptione){
e.printStackTrace();
}finally{
try{
connection.close();
}catch(Exceptione){
e.printStackTrace();
}
}
}
}
其中还需要在web.xml中进行配置
<?xmlversion="1.0"encoding="UTF-8"?> <web-appversion="3.0" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"> <display-name></display-name> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> <servlet> <servlet-name>CheckServlet</servlet-name> <servlet-class>CheckServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>CheckServlet</servlet-name> <url-pattern>/CheckServlet</url-pattern> </servlet-mapping> </web-app>
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持毛票票。