http://www.ibm.com/developerworks/cn/java/j-lo-comet/
另一篇
http://www.oschina.net/code/snippet_126858_20988
http://www.cnblogs.com/jifeng/p/4676903.html
http://www.360doc.com/content/10/1221/15/4996385_80090471.shtml
http://my.oschina.net/caiyuan/blog/12318