Spring JDBC — JdbcClient (Spring Framework 7+)

Apply Spring JDBC guidelines with JdbcClient as the default; use JdbcTemplate / NamedParameterJdbcTemplate only for legacy code or APIs not covered by JdbcClient (batch updates, KeyHolder, RowCallbackHandler streaming).

What is covered in this Skill?

• Parameterized SQL (never concatenate user input)
• JdbcClient fluent API (Spring Framework 7+) — preferred for queries and updates
• Named parameters via JdbcClient; NamedParameterJdbcTemplate for legacy migration
• RowMapper, query(Class), and records
• Batch operations and generated keys (JdbcTemplate / JdbcOperations where needed)
• Safe handling of generated keys (KeyHolder; single-row JdbcClient updates)
• Service-layer @Transactional boundaries
• Read-only transactions (@Transactional(readOnly = true))
• Safe single-row access (optional() / findFirst() vs queryForObject)
• Streaming large result sets (RowCallbackHandler, ResultSetExtractor)
• DataAccessException handling (DuplicateKeyException, EmptyResultDataAccessException)
• @JdbcTest slice testing with @Sql fixtures

Scope: Apply recommendations based on the reference rules and good/bad code examples.