jQuery如何使用JSON字符串数据构造Ajax POST请求

Question

I'm trying to hit a web site endpoint from a Java servlet using HttpClient (v4.1). The endpoint expects a post request containing parameters in a JSON string, from what I can tell. I say "from what I can tell" because I have some sample jquery production code that makes successful requests to the endpoint. It looks like this:

$.ajax({
    type: "POST",
    url: "some/u/r/l",
    data: "{'keyA':'valueA','keyB':'valueB','keyC':'valueC'}",
    contentType: "application/json; charset=utf-8",
    dataType: "json",
    ...

So I'm trying to replicate this behavior from a Java servlet using HttpClient, but I'm getting ambiguous 500's from the server, so I must be creating the request incorrectly. Can anyone tell me exactly what jQuery is doing in the above code. I understand that using a JS object as value for data parameter will add the respective key-value pairs as URL parameters to the request, but what happens to the JSON string as in the above example? Where does it go?

Answer 1

The JSON string needs to be added to the request body. For HttpClient (4.1) this goes something like:

request.setEntity(new StringEntity(json, "application/json", HTTP.UTF_8));