How to set the value of a custom field via JRJC?

[Jeff Wilson]

I'm trying to use JRJC to create an issue, and I must set a custom field before that is successful. I tried searching for examples, but did not find any.

Here's the code I am using to create the issue:

    Long testIssueTypeId = getTestIssueTypeId(projectKey);

    IssueInputBuilder builder = new IssueInputBuilder()
        .setProjectKey(projectKey)
        .setIssueTypeId(testIssueTypeId)
        .setSummary(summary)
        .setDescription(description);

    IssueInput input = builder.build();

    return jira.getIssueClient().createIssue(input).claim();

 To the list of attributes, I need to set a custom field called "Application". In the JSON of a similar issue it appears like this:

{
  "self": "https://jira.web.labs.att.com/rest/api/2/customFieldOption/14314",
  "value":"NA:12345",
  "id": "14314",
  "disabled": false
}

What code do I need to add to the IssueInputBuilder to set this field's value? Or is there another, more preferred approach?

Thanks!

EDIT:

Here's what I've tried (for another custom field):

    IssueInputBuilder builder = new IssueInputBuilder()
        .setProjectKey(projectKey)
        .setIssueTypeId(testIssueTypeId)
        .setSummary(summary)
        .setDescription(description)
        .setFieldValue("Test Type", 
           new CustomFieldOption(14314L, null, "Functional", null, null));

With this code, I get the following error:

RestClientException{statusCode=Optional.of(400), errorCollections=[ErrorCollection{status=400, errors={Test Type=Field 'Test Type' cannot be set. It is not on the appropriate screen, or unknown.}, errorMessages=[]}]}