This example shows a strange behavior of the Elasticsearch TransportClient in version 5.6.11

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>toyexample</groupId>
    <artifactId>es-tester</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <dependency>
            <groupId>org.testcontainers</groupId>
            <artifactId>testcontainers</artifactId>
            <version>1.8.0</version>
        </dependency>
        <dependency>
            <groupId>org.elasticsearch</groupId>
            <artifactId>elasticsearch</artifactId>
            <version>5.6.11</version>
        </dependency>
        <dependency>
            <groupId>org.elasticsearch.client</groupId>
            <artifactId>transport</artifactId>
            <version>5.6.11</version>
        </dependency>
        <dependency>
            <groupId>org.elasticsearch.client</groupId>
            <artifactId>elasticsearch-rest-high-level-client</artifactId>
            <version>5.6.11</version>
        </dependency>
    </dependencies>
</project>

PutStoredScriptExample.java

package test;

import org.apache.http.HttpEntity;
import org.apache.http.HttpHost;
import org.apache.http.entity.ContentType;
import org.apache.http.nio.entity.NStringEntity;
import org.apache.http.util.EntityUtils;
import org.elasticsearch.client.Response;
import org.elasticsearch.client.RestClient;
import org.elasticsearch.client.transport.TransportClient;
import org.elasticsearch.common.bytes.BytesArray;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.common.transport.InetSocketTransportAddress;
import org.elasticsearch.common.xcontent.XContentType;
import org.elasticsearch.transport.client.PreBuiltTransportClient;
import org.testcontainers.containers.GenericContainer;

import java.io.IOException;
import java.net.InetAddress;
import java.util.Collections;
import java.util.Map;

public class PutStoredScriptExample {
  public static void main(String[] args) throws IOException {

    // start an ES node, a transport client, and a rest client

    GenericContainer service =
        new GenericContainer("docker.elastic.co/elasticsearch/elasticsearch:5.6.11")
            .withEnv("xpack.security.enabled", "false")
            .withExposedPorts(9200, 9300);

    service.start();

    String ip = service.getContainerIpAddress();

    RestClient restClient =
        RestClient.builder(new HttpHost(ip, service.getMappedPort(9200), "http")).build();

    Settings settings = Settings.builder().put("cluster.name", "docker-cluster").build();
    TransportClient transportClient =
        new PreBuiltTransportClient(settings)
            .addTransportAddress(
                new InetSocketTransportAddress(
                    InetAddress.getByName(ip), service.getMappedPort(9300)));

    // store a script using the transport client

    String scriptSource = "{\"size\": 6,\"query\": {\"match_all\": {}}}";
    transportClient
        .admin()
        .cluster()
        .preparePutStoredScript()
        .setId("TEST1")
        .setLang("mustache")
        .setContent(new BytesArray(scriptSource), XContentType.JSON)
        .get();

    // actually stored is only the first field of the source!
    // this prints:
    // {"_id":"TEST1","found":true,"script":{"lang":"mustache","source":"{\"size\":6}"}}

    Response response = restClient.performRequest("GET", "/_scripts/TEST1");
    System.out.println(EntityUtils.toString(response.getEntity()));

    // we swap the field order in the source..

    scriptSource = "{\"query\": {\"match_all\": {}},\"size\": 6}";
    transportClient
        .admin()
        .cluster()
        .preparePutStoredScript()
        .setId("TEST2")
        .setLang("mustache")
        .setContent(new BytesArray(scriptSource), XContentType.JSON)
        .get();

    // now only the query is stored - the size field is ignored!
    // this prints:
    // {"_id":"TEST2","found":true,"script":{"lang":"mustache","source":"{\"query\":{\"match_all\":{}}}"}}

    response = restClient.performRequest("GET", "/_scripts/TEST2");
    System.out.println(EntityUtils.toString(response.getEntity()));

    // we try to store the same script using the rest client

    Map<String, String> params = Collections.emptyMap();
    String body = "{\"script\":{\"lang\":\"mustache\",\"source\":" + scriptSource + "}}";
    HttpEntity entity = new NStringEntity(body, ContentType.APPLICATION_JSON);
    restClient.performRequest("PUT", "/_scripts/TEST3", params, entity);

    // using the rest client the whole script with query and size fields is stored..
    // this prints:
    // {"_id":"TEST3","found":true,"script":{"lang":"mustache","source":"{\"query\":{\"match_all\":{}},\"size\":6}","options":{"content_type":"application/json; charset=UTF-8"}}}

    response = restClient.performRequest("GET", "/_scripts/TEST3");
    System.out.println(EntityUtils.toString(response.getEntity()));

    // as it turned out, the trick is to wrap the script source in a script element..
    // see: https://discuss.elastic.co/t/scripts-stored-via-transportclient-lose-fields-in-source/148473/3

    transportClient
            .admin()
            .cluster()
            .preparePutStoredScript()
            .setId("TEST4")
            .setLang("mustache")
            .setContent(new BytesArray("{\"script\":" + scriptSource + "}"), XContentType.JSON)
            .get();

    // and - tadaa - the whole script with query and size fields is stored!
    // this prints:
    // {"_id":"TEST4","found":true,"script":{"lang":"mustache","source":"{\"query\":{\"match_all\":{}},\"size\":6}"}}

    response = restClient.performRequest("GET", "/_scripts/TEST4");
    System.out.println(EntityUtils.toString(response.getEntity()));

    transportClient.close();
    restClient.close();
    service.stop();
    service.close();
  }
}