UserAction:
package
com.vo;

import
org.hibernate.Query;
import
org.hibernate.Session;

import
com.HibernateSessionFactory;

public
class
UserAction

{
private Session session;
public UserAction()

{
session = HibernateSessionFactory.getSession();
}
//判断用户是否存在方法的方法
public User exists(String username)

{
User entity = null;
Query q = session.createQuery("from User u where u.username = ? ");
q.setString(0, username);
if(q.list().size() > 0)

{
entity = (User) q.list().get(0);
}
return entity;
}
}
index.jsp:
<%
@ page pageEncoding="GB18030"
%>
<
html
>
<
head
>
<
title
>
test
</
title
>
<
script
type
='text/javascript'
src
='/ajax01/dwr/interface/service.js'
></
script
>
<
script
type
='text/javascript'
src
='/ajax01/dwr/engine.js'
></
script
>

<
script
type
="text/javascript"
>
//定义一个方法,用于前台调用
function exists()

{
var name = document.getElementById("username");
//action的exists方法,可以直接调用,第一参数是需要传入的值
//第二参数是回调函数(异步处理嘛)
service.exists(name.value,callback);
}
//回调函数(形参是service.exists方法的返回值,这里是vo
function callback(user)

{
if(user == null)

{
alert('y');
}
else

{
alert('n');
}
}
</
script
>
<
body
>
<
form
action
="#"
method
="post"
>
<
input
type
="text"
name
="username"
id
="username"
onblur
="exists();"
/><
div
id
="username_info"
></
div
>
<
input
type
="submit"
/>
</
form
>
</
body
>
</
html
>
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