错误描述：项目中所有用到dwr的地方，都显示“Session Error”错误

解决方法：在web.xml中添加

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

于是，完整的dwr配置如下：

	<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>
    <load-on-startup>1</load-on-startup>
    
    <init-param>   
    <param-name>crossDomainSessionSecurity</param-name>
    <param-value>false</param-value>
   </init-param>
   
  </servlet>

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