HttpClient连接池
http://rd-030.iteye.com/blog/2320490，http://www.cnblogs.com/lodor/p/6775112.html，http://blog.csdn.net/love_linney/article/details/31471847，http://blog.sina.com.cn/s/blog_b3bf01600102wdfj.html
http://rd-030.iteye.com/blog/2320490，http://www.cnblogs.com/lodor/p/6775112.html，http://blog.csdn.net/love_linney/article/details/31471847，http://blog.sina.com.cn/s/blog_b3bf01600102wdfj.html
