Only return specific fields in elastic search native query Java api - elasticsearch

Question

I'm building a native query but I only want to return certain fields, all of which are held within a parent field. I think I am looking for the QueryBuilders or NativeSearchQueryBuilder equivalent of the REST API's _source. Here's a code example:
NativeSearchQueryBuilder sb = new NativeSearchQueryBuilder()
.withIndices("myIndex")
.withTypes("myType")
.withQuery(QueryBuilders.queryStringQuery("parent.field2:Foo*"));
.withFields("parent.field1");
I'd expect this to return a list of only parent.field1 that are associated with objects that have parent.field2 like Foo*. But it returns nothing.
Thanks for any help!

Answer 1

After some research, I found the answer is in NativeSearchQueryBuilder. I was just using an older version of spring-data elastic search, so I could not see this method: withSourceFilter. The way to do this is:
NativeSearchQueryBuilder sb = new NativeSearchQueryBuilder()
.withIndices("myIndex")
.withTypes("myType")
.withQuery(QueryBuilders.queryStringQuery("parent.field2:Foo*"));
.withSourceFilter(new FetchSourceFilter(<String array of includes>, null));
FetchSourceFilter takes 2 arguments, a String[] array of includes and one of excludes. In my example, I'd have an array like new String[]{"parent.field1"} passed to FetchSourceFilter, which in turn is passed to withSourceFilter. The search above will then return (once built and ran) a list of parent.field1 with parent.field2 like Foo*.
The version I upgraded to was spring-data-elasticsearch 2.0.2.