A request has been denied as a potential CSRF attack.”

 当输入账号和密码，点击登录，出现“session error”。

后来在网上发现了这个问题解决办法。

在web.xml配置文件中修改dwr的配置：

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun/xml/ns/javaee"
	xmlns:xsi="http://www.w3/2001/XMLSchema-instance"
	xsi:schemaLocation="http://java.sun/xml/ns/javaee 
	http://java.sun/xml/ns/javaee/web-app_2_5.xsd">
	<welcome-file-list>
		<welcome-file>/qiantai/index1.jsp</welcome-file>
	</welcome-file-list>


	



	<servlet>
		<servlet-name>dwr-invoker</servlet-name>
		<servlet-class>org.directwebremoting.servlet.DwrServlet</servlet-class>
		<init-param>
			<param-name>debug</param-name>
			<param-value>true</param-value>
		</init-param>
		<init-param>
			<param-name>activeReverseAjaxEnabled</param-name>
			<param-value>true</param-value>
		</init-param>
		<init-param>
			<param-name>initApplicationScopeCreatorsAtStartup</param-name>
			<param-value>true</param-value>
		</init-param>
		<init-param>
			<param-name>maxWaitAfterWrite</param-name>
			<param-value>500</param-value>
		</init-param>
		<init-param>
			<param-name>crossDomainSessionSecurity</param-name>
			<param-value>false</param-value>
		</init-param>
		<load-on-startup>1</load-on-startup>

	</servlet>

	<servlet-mapping>
		<servlet-name>dwr-invoker</servlet-name>
		<url-pattern>/dwr/*</url-pattern>
	</servlet-mapping>



	
</web-app>

在配置文件中一定要加上这句话，问题就可以解决

 <init-param>      
            <param-name>crossDomainSessionSecurity</param-name>      
            <param-value>false</param-value>      
    </init-param>  

配置好之后，然后重新启动服务器，就可以登录成功。