DWR的三种Reverse Ajax Mode配置详解

Dwr的Reverse Ajax可分为两中基本的mode.一种是Active,另一种是Passive,在Active中又分为三种.

Full Streaming Mode

Early Closing Mode

Polling Mode

在DWR应用中.默认启用的是Full Streaming Mode .它是三种modes中最快的一种.它每60秒检查一次浏览器是否是活跃的.配置很简单:

< servlet >
   < servlet-name > dwr-invoker </ servlet-name >
   < servlet-class > org.directwebremoting.servlet.DwrServlet </ servlet-class >
   < init-param >
     < param-name > activeReverseAjaxEnabled </ param-name >
     < param-value > true </ param-value >
   </ init-param >
</ servlet >

然后在要使用Reverse Ajax的页面使用

dwr.engine.setActiveReverseAjax( true );

即可...在2.0.4以后的版本中还要加入

< init-param >
   < param-name > maxWaitAfterWrite </ param-name >
   < param-value > -1 </ param-value >
</ init-param >

因为在2.0.4版本中默认是使用Early Closing Mode

Early Closing Mode:
在2.0.4以后的版本中不需要添加配置..而2.0.3以前的版本需要、添加

< init-param >
   < param-name > maxWaitAfterWrite </ param-name >
   < param-value > 500 </ param-value >
</ init-param >

If it is deemed unwise to hold connections open at all then DWR can use polling mode

 

< init-param >
   < param-name > org.directwebremoting.extend.ServerLoadMonitor </ param-name >
   < param-value > org.directwebremoting.impl.PollingServerLoadMonitor </ param-value >
</ init-param >

In polling mode the default poll rate is every 5 seconds. This can be customized using the following:

 
 

  
  
  
  <
  
  init-param
  
  >
  
  
   
  
  <
  
  param-name
  
  >
  
  disconnectedTime
  
  </
  
  param-name
  
  >
  
  
   
  
  <
  
  param-value
  
  >
  
  60000
  
  </
  
  param-value
  
  >
  
  
 
  
  </
  
  init-param
  
  >
  
  
 
 
 

The example above will poll only once every 60 seconds (60,000 milliseconds). For many applications a response time of 60 seconds will be enough, and will allow a web server to handle a very large number of clients.

测试环境:IE8.0,Firefox 2.0,Windows xp sp2,Tomcat 6.0,MsSQL Server 2000
使用技术:Spring,Hibernate.Ext.DWR
用第一种配置的时候IE运行不了.报异常 "要完成操作的数据尚未准备好",Firefox可以.
第二种配置在maxWaitForWrite少于200的情况下IE运行正常,Firefox运行正常.
第三种配置只能打开一个连接.再想打开第二个则会报   java.lang.IllegaStateException:Cannot create a session after response has been commited
很是郁闷...若将maxWaitForWrite设置为100.则两个浏览器均没问题..但是浏览器久无刷新动作就无法从服务器调用客户端
这篇文章望抛砖引玉..各位讲下你们是如何配置的

 

参考资料:http://getahead.org/dwr/reverse-ajax/configuration