例如访问百度的Http请求头如下，需要构建出一个请求对象。
GET http://www.baidu.com/index.php?tn=monline_5_dg HTTP/1.1
Host: www.baidu.com
User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:34.0) Gecko/20100101 Firefox/34.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: zh-cn,zh;q=0.8,en-us;q=0.5,en;q=0.3
Accept-Encoding: gzip, deflate
Referer: http://offlintab.firefoxchina.cn/
Cookie: BAIDUID=BC03B88D10EED1B0024D570C778238F2:FG=1; BAIDUPSID=BC03B88D10EED1B0024D570C778238F2; BD_HOME=0; H_PS_PSSID=1449_10251_10443_10120_10209_10017_10178_9498_10052_9105_10355_9094_10095_10008_10256_9979_9023; BD_UPN=13314552; BDRCVFR[kpkBv0s1F-3]=G01CoNuskzfuh-zuyuEXAPCpy49QhP8
Connection: keep-alive
Cache-Control: max-age=0
