How to retrieve stored fields using spring-data-opensearch with _source disabled?

OpenSearch Client Libraries
2

I think for your case, when constructing NativeSearchQuery, withStoredFields should be used instead of withFields:

NativeSearchQuery searchQuery = new NativeSearchQueryBuilder()
        .withQuery(QueryBuilders.termQuery("_id", documentId))
        .withStoredFields(storedFields)
        .build();