@Grab(group='org.elasticsearch.client', module='transport', version='5.0.2')
@Grab(group='org.apache.logging.log4j', module='log4j-core', version='2.6.2')
@Grab(group='org.apache.logging.log4j', module='log4j-api', version='2.6.2')

import org.elasticsearch.action.admin.indices.create.CreateIndexAction
import org.elasticsearch.action.admin.indices.create.CreateIndexRequestBuilder
import org.elasticsearch.action.index.IndexAction
import org.elasticsearch.action.index.IndexRequestBuilder
import org.elasticsearch.action.search.SearchResponse
import org.elasticsearch.action.support.WriteRequest
import org.elasticsearch.client.transport.TransportClient
import org.elasticsearch.common.settings.Settings
import org.elasticsearch.common.transport.InetSocketTransportAddress
import org.elasticsearch.transport.Netty4Plugin
import org.elasticsearch.transport.client.PreBuiltTransportClient
import org.elasticsearch.indices.IndexAlreadyExistsException

import java.time.Instant

import static org.elasticsearch.common.xcontent.XContentFactory.jsonBuilder
import static org.elasticsearch.index.query.QueryBuilders.matchAllQuery

List<String> hostAndPort = ['localhost:9300']
Settings settings = Settings.builder()
                .put("cluster.name", "elasticsearch")
                .build()
TransportClient client = new PreBuiltTransportClient(settings, Collections.emptyList())
hostAndPort.each { spec ->
            def (host,port) = spec.split(':')
            if (!port) {
                port = '9300'
            }
            client.addTransportAddress(new InetSocketTransportAddress(InetAddress.getByName(host), Integer.valueOf(port)))
}

CreateIndexRequestBuilder createIndexRequestBuilder = new CreateIndexRequestBuilder(client, CreateIndexAction.INSTANCE)
        .setIndex("test")
        .addMapping("test", jsonBuilder().startObject()
                                 .startObject("properties")
                                      .startObject("doc_date")
                                      .field("type", "date")
                                      .field("format", "strict_date_optional_time||epoch_millis")
                                      .field("store", true)
                                      .endObject()
                                 .endObject()
                             .endObject())                            
try {
  createIndexRequestBuilder.execute().actionGet()
} catch (IndexAlreadyExistsException e) {
}

IndexRequestBuilder indexRequestBuilder = new IndexRequestBuilder(client, IndexAction.INSTANCE)
                .setIndex("test")
                .setType("test")
                .setId("1")
                .setSource(jsonBuilder().startObject().field("doc_date", Instant.now()).endObject())
                .setRefreshPolicy(WriteRequest.RefreshPolicy.IMMEDIATE)

indexRequestBuilder.execute().actionGet()

SearchResponse response = client.prepareSearch()
  .setQuery(matchAllQuery())
  .addStoredField("doc_date")
  .execute().actionGet()

println response

response.hits.hits.each { hit ->
    println hit.fields.get("doc_date").value()
    Instant instant = Instant.parse(hit.fields.get("doc_date").value())
    long millis = instant.toEpochMilli()
    println millis
}