How is a POST with parameters accomplished using the Google HTTP Java client library?

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How is a POST with parameters accomplished using the Google HTTP Java client library?

This does not work:

 public void run() throws Exception {

      HttpRequestFactory requestFactory

              = new NetHttpTransport().createRequestFactory();

      String myPostURL = "https://my-post-url" 

      //String params = "{'userid': 'me', 'password': 'mk8e!'}";

      String params = "{\"userid\": \"me\", \"password\": \"mk8e!\"}";

      HttpContent content = ByteArrayContent.fromString("application/json", params);

  

      GenericUrl url = new GenericUrl(myPostURL);

      HttpRequest request = requestFactory.buildPostRequest(url, content);

      HttpResponse response = request.execute();

   }

   

I get a message back from the server:

Bad request.  Parameter userid not found.  Parameter password not found

at com.google.api.client.http.HttpRequest.execute(HttpRequest.java:1113)

google-http-java-client