1。02checkUsername.html文件:
<!DOCTYPE html>
<html>
<head>
<title>檢查用戶名是否可用</title>
<meta name="keywords" content="keyword1,keyword2,keyword3">
<meta name="description" content="this is my page">
<meta name="content-type" content="text/html; charset=UTF-8">
<!--<link rel="stylesheet" type="text/css" href="./styles.css">-->
<script type="text/javascript" src="util.js"></script>
<script type="text/javascript">
window.οnlοad=function(){
document.getElementById("name").οnblur=function(){
//發異步請求
var xhr = getXmlHttpRequest();
xhr.onreadystatechange=function(){
if(xhr.readyState==4){
if(xhr.status==200){
//獲取響應正文
document.getElementById("msg").innerHTML=xhr.responseText;
}
}
}
//get異步請求
//xhr.open("GET","/Ajax_Project/servlet/ServletDemo2?time="+new Date().getTime()+"&name="+this.value);
//xhr.send(null);
//post異步請求
xhr.open("POST","/Ajax_Project/servlet/ServletDemo2?time="+new Date().getTime());
xhr.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
xhr.send("name="+this.value);
}
}
</script>
</head>
<body>
用戶名:<input type="text" id="name" name="name"/><span id="msg"></span>
</body>
</html>
2。ServletDemo2.java文件:
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class ServletDemo2 extends HttpServlet {
private List<String> names = new ArrayList<String>();
public void init()throws ServletException{
names.add("www");
names.add("yyy");
names.add("mmm");
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");//告知客戶端是文本
PrintWriter out = response.getWriter();
String name = request.getParameter("name");//獲取用戶輸入的數據
if(names.contains(name)){
//存在
out.write("<font color='red'>用戶名已經存在</font>");
}else{
//不存在
out.write("<font color='green'>用戶名可以使用</font>");
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
3。util.js文件:
function getXmlHttpRequest() {
var xhr;
try {
// Firefox, Opera 8.0+, Safari
xhr = new XMLHttpRequest();
} catch (e) {
// Internet Explorer
try {
xhr = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
try {
xhr = new ActiveXObject("Microsoft.XMLHTTP");
} catch (e) {
alert("您的瀏覽器不支持AJAX!");
return false;
}
}
}
return xhr;
}
4。web.xml文件:
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5"
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_2_5.xsd">
<display-name></display-name>
<servlet>
<servlet-name>ServletDemo1</servlet-name>
<servlet-class>ServletDemo1</servlet-class>
</servlet>
<servlet>
<servlet-name>ServletDemo2</servlet-name>
<servlet-class>ServletDemo2</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>ServletDemo1</servlet-name>
<url-pattern>/servlet/ServletDemo1</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>ServletDemo2</servlet-name>
<url-pattern>/servlet/ServletDemo2</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>
運行:http://localhost:8080/Ajax_Project/02checkUsername.html
輸出www時的運行結果:
輸入aaa時的運行結果: