https://www.igvita.com/2011/05/27/streamsql-event-processing-with-esper/
http://torycatkin.iteye.com/blog/1343596
http://blog.csdn.net/yixuan_1/article/category/1908125
http://blog.csdn.net/xiaohulunb/article/details/38538815
http://docs.fluentd.org/articles/cep-norikra
http://esper.codehaus.org/tutorials/solution_patterns/solution_patterns.html#aggregate-0
原文：http://www.cnblogs.com/diyunpeng/p/4141881.html