fix(jdbc-v2): support explicit FORMAT JSON queries

[014-code]

Summary

• support explicit FORMAT JSON queries in JDBC v2
• expose the server-rendered JSON through a streaming, single-column
  ResultSet named results
• return one JDBC row for each line in the JSON response
• preserve the existing FORMAT JSONEachRow and default
  RowBinaryWithNamesAndTypes paths
• update the JDBC v2 feature contract and changelog

Problem

JDBC v2 rejects queries with an explicit JSON output format:

Issue

Related #2715.

After migrating from the legacy JDBC driver to JDBC v2, queries that explicitly
request ClickHouse's JSON output format fail in executeQuery():

SELECT 1 AS x FORMAT JSON

[chernser]

@014-code

thank you for the contribution!

However we plan to support JSON format in another way because it has metadata and data in one document.
I've commented in the original issue.
Current problem is to make some call with internal client and get result. But for this com.clickhouse.jdbc.ConnectionImpl#getClient can be used.

[014-code]

@014-code

thank you for the contribution!

However we plan to support JSON format in another way because it has metadata and data in one document. I've commented in the original issue. Current problem is to make some call with internal client and get result. But for this com.clickhouse.jdbc.ConnectionImpl#getClient can be used.

Thanks for the clarification.

I understand. I'll take a look at implementing it using ConnectionImpl#getClient() instead of handling the HTTP response directly.

[chernser]

This is very inefficient way of parsing JSON - every JSON library supports reading from input stream.
Please provide example where it is demonstrated for example with Jackson library.
Besides JSON format (https://clickhouse.com/docs/reference/formats/JSON/JSON) has meta and data separated - so users need some instructions how to handle them.

[chernser]

It is not document oriented, I'd say. It is just JSON format output with very ClickHouse specific structure https://clickhouse.com/docs/reference/formats/JSON/JSON

[chernser]

we use tests as reference implementation sometimes. This test do not fit this needs.
Please align it with example in the document.

[014-code]

Thank you for the clarification. I’ve updated the PR accordingly in 2636d7e.
Reworded the documentation to describe FORMAT JSON as ClickHouse-specific JSON output rather than document-oriented output.
Replaced the line-by-line string collection with a Jackson example that parses QueryResponse#getInputStream() directly.
The example and integration test now handle the meta and data fields separately, including column metadata and row values.
Added a note to use Jackson’s streaming JsonParser for large data arrays.
The JDBC ResultSet behavior remains unchanged; this only documents and verifies access through ConnectionImpl#getClient() as discussed.