<li>
	<div class="inputInfo">
		<span>帐号</span>
                <input type="text" value="" class="inputText" id="name"/>
        </div>
</li>
<li>
	<div class="inputInfo">
		<span>密码</span>
                <input type="password" class="inputText" id="password"/>
	</div>
</li>

<!-- 显示返回文本字符串 -->
<div id="showResponseText"></div>

// JavaScript Document
utils={
	createRequest:function(){
		var request ;
		try{
			request = new XMLHttpRequest();
			}catch(tryMS){
				try{
					request = new ActiveXObject("Msxml2.XMLHTTP");
					}catch(otherMS){
						try{
							request = new ActiveXObject("Microsoft.XMLHTTP");
							}catch(failed){
								request = null;
								}
						}
				} 
		return request;
		}
	};

// JavaScript Document

register={
	init:function(){
		document.getElementById('name').onblur = register.checkUserName;
		},
	checkUserName:function(){
		request = utils.createRequest();
		if(request ==  null){
			alert("create request failed");
			}
		else{
			var nameValue = document.getElementById('name').value;
			var url = "ajax_register!checkUserName?userName="+nameValue;		
			request.onreadystatechange = register.showUserNameStatus;
			
			request.open("post",url,true);
			
			request.send(null);
			}
		},
	
	showUserNameStatus:function(){
		if(request.readyState == 4){
			if(request.status ==200){
				document.getElementById("ppt").innerHTML=request.responseText;
				}
			}
		}
	};

window.onload = register.init;

<action name="ajax_register" class="customer.action.Ajax_RegisterAction">
		<result type="stream">
			<param name="contentType">text/plain</param>
			<param name="inputName">inputStream</param>
		</result>
</action>

import java.io.InputStream;
import java.io.StringBufferInputStream;

import com.opensymphony.xwork2.ActionSupport;

import customer.service.Register;
import customer.service.RegisterImpl;

public class Ajax_RegisterAction extends ActionSupport {

/**
 * 
 */
private static final long serialVersionUID = 1L;

private InputStream inputStream;


public InputStream getInputStream() {
	return inputStream;
}


public void setInputStream(InputStream inputStream) {
	this.inputStream = inputStream;
}


// service类
private Register register = new RegisterImpl();

private String userName;


public String getUserName() {
	return userName;
}

// 检查userName是否重复
public String checkUserName(){
	String text ="";
	if(!register.checkNameExist(userName)){
		text = "yes";
	}else{
		text = "no";
	}
	getResponseText(text);
	return SUCCESS;
}

// 获取返回文本
public void getResponseText(String text){
	inputStream = new StringBufferInputStream(text);
}