# Converting JsonData to Map in new ES Java Client

**URL:** <https://discuss.elastic.co/t/converting-jsondata-to-map-in-new-es-java-client/379724>\
**Category:** Elasticsearch\
**Tags:** language-clients\
**Created:** [July 2, 2025, 9:11pm UTC](https://discuss.elastic.co/t/converting-jsondata-to-map-in-new-es-java-client/379724 "2025-07-02T21:11:25Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Sai\_Satwik\_Kuppili](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/sai_satwik_kuppili/32/98048_2.png) [@Sai\_Satwik\_Kuppili](https://discuss.elastic.co/u/Sai_Satwik_Kuppili)\
**Post date:** [July 2, 2025, 9:11pm UTC](https://discuss.elastic.co/t/converting-jsondata-to-map-in-new-es-java-client/379724/1 "2025-07-02T21:11:25Z")

</div>

Hello everyone,

I'm working with the new Elasticsearch Java Client and need to convert a `Hit` 's `_source` (provided as `JsonData` ) into a `Map<String, Object>` . The previous Rest High-Level Client offered `SearchHit.getSourceAsMap()` , but I require a reliable equivalent in the new client for dynamic field access without POJOs.

**Here's the problem:**

Using `hit.source().to(Map.class)` within a loop processing `TopHitsAggregate` results, like:

```auto
// ... inside a loop processing TopHitsAggregate results
List<Map<String, Object>> hits = new ArrayList<>();
for (Hit<JsonData> hit : topHitsResult.hits().hits()) {
    assert hit.source() != null;
    Map<String, Object> mappingJson = hit.source().to(Map.class); // This line
    hits.add(populateProtectionField(mappingJson)); // populateProtectionField is a custom method
}

```

This approach causes unexpected type issues or incorrect deserialization for nested fields in the `_source` document. While `hit.source().toMap()` correctly provides a `Map<String, Object>` with nested structures, my ultimate goal is to simplify certain fields.

**Sample Response :**

```auto
{
  "display_name": {
    "chars": "Default Layer3 Section",
    "string": "Default Layer3 Section",
    "valueType": "STRING"
  }
}

```

**Desired Final Output (Transformed `Map<String, Object>` ):**

```auto
{
  "display_name": "Default Layer3 Section"
}

```

Could you confirm `hit.source().toMap()` is the correct and robust approach for the initial deserialization, and then advise on best practices for subsequently transforming a nested `Map<String, Object>` (like the one for `display_name` ) into a flattened structure as shown in my desired output? Insights into why `hit.source().to(Map.class)` is problematic for complex JSON are also appreciated! Thank you.

---

<div class="post-metadata">

**Author:** ![ltrotta](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/ltrotta/32/124003_2.png) [@ltrotta](https://discuss.elastic.co/u/ltrotta)\
**Post date:** [July 11, 2025, 10:15am UTC](https://discuss.elastic.co/t/converting-jsondata-to-map-in-new-es-java-client/379724/3 "2025-07-11T10:15:58Z")

</div>

Hello!

`hit.source().to(Map.class)` is indeed the recommended way to convert `JsonData` into a `Map`.

For your specific case, you could provide a custom deserializer that would automatically parse the `JsonData` into the flattened map, by creating a custom implementation of `JsonpDeserializer` and then calling `hit.source().deserialize(YourJsonpDeserializer<Map>)`, but considering the complexity and the fact that you'd have to hardcode the names of the fields in the deserializer anyways, I'd suggest simply iterating over the map and converting the values one by one to your desired output.

> This approach causes unexpected type issues or incorrect deserialization for nested fields in the `_source` document

Could you provide an example of this? I've tried deserializing nested fields and I'm obtaining nested maps, as expected. Maybe working with POJOs could help, by making the nested fields more easily readable; you can create a custom class matching the output of `source`and then convert the `JsonData` like you do with the map, so `hit.source().to(CustomClass.class, jsonpMapper)` (where the jsonMapper is the same used to create the client).