Jira calls external REST Service - rest

Question

My Problem: I want to introduce a new field in JIRA with status information from external REST Service (response is json).
Plan: Every Jira issue has a input field with some reference string. Behind this field there should be a panel, what should display informations from the external REST call (parsing response JSON is required).
Can someone give me some good info pages, how to tell JIRA to call external REST Service?

Answer 1

If you don't want to build it see:
nFeed
HTTP Feed Custom Field
If you want to build it yourself then start by following this tutorial on Creating a custom field type which is to more or less store a basic String within the database. (This would be the reference string)
You then have two options, the first is within the JiraCustomField class override the getVelocityParameters which was taken from How to call a java method from velocity Atlassian Answers question.
Then create a method (fetchValueFromWebService(String val)) that you would call that would contain code to query the REST Service based off the fields value that would be passed in from the velocity template. (E.g. $instance.fetchValueFromWebService($value))
To perform the actual web service call you can use any library you want, just see the Managing Dependencies documentation so it gets included in the plugin. (For example using the Jira Jersey version see this)
Your other option would be to within the view-basictext.vm have it use javascript and perform an AJAX to the web service by calling a function in your own JS file and dump that into a span that you have defined: (See Including Javascript and CSS resources)
<span id="webServiceValue"></span>
<script type="text/javascript">
fetchValueFromWebService($value);
</script>
You would however need to ensure that the webservice has Cross-origin resource sharing (CORS) enabled if you go the AJAX route.