active_choice_from_url

// Import the JsonSlurper class to parse Dockerhub API response
import groovy.json.JsonSlurper

// Set the URL we want to read from, it is MySQL from official Library for this example, limited to 20 results only.
docker_image_tags_url = "https://hub.docker.com/v2/repositories/library/mysql/tags/?page_size=20"
try {
    // Set requirements for the HTTP GET request, you can add Content-Type headers and so on...
    def http_client = new URL(docker_image_tags_url).openConnection() as HttpURLConnection
    http_client.setRequestMethod('GET')
    // Run the HTTP request
    http_client.connect()
    // Prepare a variable where we save parsed JSON as a HashMap, it's good for our use case, as we just need the 'name' of each tag.
    def dockerhub_response = [:]    
    // Check if we got HTTP 200, otherwise exit
    if (http_client.responseCode == 200) {
        dockerhub_response = new JsonSlurper().parseText(http_client.inputStream.getText('UTF-8'))
    } else {
        println("HTTP response error")
        System.exit(0)
    }
    // Prepare a List to collect the tag names into
    def image_tag_list = []
    // Iterate the HashMap of all Tags and grab only their "names" into our List
    dockerhub_response.results.each { tag_metadata ->
        image_tag_list.add(tag_metadata.name)    
    }
    // The returned value MUST be a Groovy type of List or a related type (inherited from List)
    // It is necessary for the Active Choice plugin to display results in a combo-box
    return image_tag_list.sort()
} catch (Exception e) {
         // handle exceptions like timeout, connection errors, etc.
         println(e)
}