commons-httpclient是apache的老项目,最后版本是3.1,不再建议使用。

最新的httpclient是属于Apache HttpComponents 下面的一个子项目,分为HttpClientHttpCore两个部分,API库更丰富,同时包含server和client端的API, 其版本号从4.0开始。新项目应该使用该版本。

参考:
http://stackoverflow.com/questions/5153434/what-the-relationship-between-commons-httpclient-and-httpclient-both-from-apache , about the question
http://hc.apache.org/, Apache HttpComponents
http://hc.apache.org/httpclient-legacy/index.html , httpclient history
http://hc.apache.org/httpcomponents-client-ga/index.html , new httpclient features