Ajax dwr框架 错误req未定义

麻烦高手帮忙查下错：
dwr javascript调用java
java类
package com.kuyi.util;

import javax.servlet.http.HttpServletRequest;

import org.directwebremoting.WebContextFactory;

public class Request {
public HttpServletRequest getRequest() {
HttpServletRequest request = null;
try {
request = WebContextFactory.get().getHttpServletRequest();

} catch (Exception e) {
e.printStackTrace();
}
return request;
}

}

配置文件
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE dwr PUBLIC "-//GetAhead Limited//DTD Direct Web Remoting 2.0//EN" "http://www.getahead.ltd.uk/dwr/dwr20.dtd">
<dwr>
<allow>
<create creator="new" javascript="Operation">
<param name="class" value="com.kuyi.service.Operation" />
</create>

<create javascript="req" creator="new">
<param name="class" value="com.kuyi.util.Request" />
</create>
</allow>
</dwr>

html中javascript代码
function getRequest(){
req.getRequest(requestCallBack);
}

function requestCallBack(data){
return data;