jmeter发送的post请求，可以是json请求，和普通的post请求稍微有点区别，那么怎么用jmeter发送json请求呢？
首先要找一个json请求的例子，这个例子是携程网搜索机票，
网址为：http://www.ctrip.com/
就会看到一个请求
POST http://flights.ctrip.com/itinerary/api/12808/products HTTP/1.1
Host: flights.ctrip.com
Connection: keep-alive
Content-Length: 394
Origin: http://flights.ctrip.com
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.106 Safari/537.36
Content-Type: application/json
Accept: */*
Referer: http://flights.ctrip.com/itinerary/roundtrip/SZX-PVG?date=2018-08-16,2018-09-03&portingToken=f4b3cccf952d430f849b09cf2f1b7142
Accept-Encoding: gzip, deflate
Accept-Language: zh-CN,zh;q=0.9,en;q=0.8
Cookie: _abtest_userid=5de22bed-c5a7-4899-9a39-d9585171b4dd; _RSG=2t4LegTggt55DEOg1rU9yA; _RDG=2832aa1c0f5c9127e73f759be773872d62; _RGUID=5deaa9da-a854-4dc2-af09-7b506a60e345; _ga=GA1.2.928472268.1516689249; Session=SmartLinkCode=U799897&SmartLinkKeyWord=&SmartLinkQuary=&SmartLinkHost=&SmartLinkLanguage=zh; DomesticUserHostCity=SZX|%c9%ee%db%da; adscityen=Shenzhen; _RF1=119.139.197.11; _gid=GA1.2.1823419760.1533784673; Union=OUID=&AllianceID=4897&SID=799897&SourceID=&Expires=1534389473325; MKT_Pagesource=PC; appFloatCnt=1; manualclose=1; _bfa=1.1516689246225.w2exd.1.1533784670751.1533792777877.13.59; _bfs=1.4; Mkt_UnionRecord=%5B%7B%22aid%22%3A%224897%22%2C%22timestamp%22%3A1533794105486%7D%5D; _jzqco=%7C%7C%7C%7C1533794085844%7C1.75043952.1516689249334.1533794085722.1533794105525.1533794085722.1533794105525.undefined.0.0.27.27; __zpspc=9.15.1533794085.1533794105.2%231%7Cbaiduppc%7Cbaidu%7Curldx%7C%25E8%25AE%25A2%25E7%25A5%25A8%25E7%25BD%2591%25E7%25AB%2599%7C%23; _bfi=p1%3D100101991%26p2%3D100101991%26v1%3D59%26v2%3D58; FD_SearchHistorty={"type":"D","data":"D%24%u6DF1%u5733%28SZX%29%24SZX%242018-08-16%24%u4E0A%u6D77%28%u6D66%u4E1C%u56FD%u9645%u673A%u573A%29%28PVG%29%24SHA%2CPVG%242018-09-03%24%24"}
{"flightWay":"Roundtrip","classType":"ALL","hasChild":false,"hasBaby":false,"searchIndex":1,"portingToken":"f4b3cccf952d430f849b09cf2f1b7142","airportParams":[{"dcity":"SZX","acity":"PVG","dcityname":"深圳","acityname":"浦东国际机场","date":"2018-08-16","dcityid":30},{"dcity":"PVG","acity":"SZX","dcityname":"浦东国际机场","acityname":"深圳","date":"2018-09-03","acityid":30}]}
可以看出请求数据是一个json字符串，这个就是一个json请求。
然后在打开jmeter，新建一个http请求
在http请求中填写内容如下图，把json串复制到BodyData 中去
添加结果树，执行请求，Response Data没有数据，说明请求不成功
请求不正常，是因为请求的header 不正确，添加header
复制请求数据中的header信息到粘贴板，点击【add from clipboard】按钮，就自动把header的键值对复制到这里，很方便。这个是jmeter 4.0，记得jmeter 3.x版本复制过去，每一行开头还多了一个空格，现在4.0 没有这个问题，算是方便不少了。
再执行请求，请求响应信息正常
这个时候，如果删除 header信息中的 Content-Type: application/json
请求又不正常，说明json请求一定要再header 中配置这一项才行
