title: How to get the response body of JSON format when using Jenkins rest api to create job?
body: <p>The .../api/json seems only working for query info with GET method. When I request /createItem?name=xxx or /createItem/api/json?name=xxx with POST method, it always return the response body of HTML。</p>
  <p>This is very inconvenient to get error information，for example, when the job already exists,it return like this <a href="https://i.stack.imgur.com/n6xGD.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/n6xGD.png" alt="enter image description here" /></a></p>