How can I set a parent / child relationship using the Elastic Search Java API?

It looks like you are not configuring your "carType" mapping to specify "roadType" as a parent.

"mappings": {    "roadType": {        "properties": {        }    },    "carType": {        "_parent": {            "type": "roadType"        },        "properties": {            "make": {                "type": "string"            },            "model": {                "type": "string"            }        }    }}

For more info, see here: https://www.elastic.co/guide/en/elasticsearch/guide/current/parent-child-mapping.html

I had to create a custom mapper for the parent / child relationship. This still preserves the dynamic mapping that can happen on document creation.

public void createRecord(Road road, Car car) throws Exception{  ObjectMapper objectMapper = new ObjectMapper();  String roadJson = objectMapper.writeValueAsString(road);  String carJson = objectMapper.writeValueAsString(car);  Client client = TransportClient.builder().build().addTransportAddress(new InetSocketTransportAddress(InetAddress.getByName("localhost"), 9300));  if(!client.admin().indices().prepareExists("myIndex").get().isExists()){      XContentBuilder xContentBuilder = XContentFactory.jsonBuilder().startObject().startObject("roadType").endObject().endObject();     XContentBuilder xContentBuilder2 = XContentFactory.jsonBuilder().startObject().startObject("carType").startObject("_parent").field("type", "roadType").endObject().endObject().endObject();     client.admin().indices().create(new CreateIndexRequest("myIndex")).get();     client.admin().indices().preparePutMapping("myIndex").setType("carType").setSource(xContentBuilder2).get();     client.admin().indices().preparePutMapping("myIndex").setType("roadType").setSource(xContentBuilder).get();  }  IndexResponse response = client.prepareIndex("myIndex", "roadType").setSource(roadJson).get();  client.prepareIndex("myIndex", "carType").setParent(response.getId()).setSource(carJson).get();}

This creates a custom mapper that sets up the parent child relationship between roadType and carType while still allowing you to dynamically map additional properties. Make sure you add the child mapping first or it won't work.