311-frameworks-spring-jdbc - Claude MCP Skill

# 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.

## Constraints

Before applying any Spring JDBC changes, ensure the project compiles. If compilation fails, stop immediately. After applying improvements, run full verification.

- **MANDATORY**: Run `./mvnw compile` or `mvn compile` before applying any change
- **SAFETY**: If compilation fails, stop immediately
- **VERIFY**: Run `./mvnw clean verify` or `mvn clean verify` after applying improvements
- **SQL INJECTION**: Never concatenate untrusted input into SQL strings — always use bind parameters
- **BEFORE APPLYING**: Read the reference for detailed rules and good/bad patterns

## When to use this skill

- Review Java code for Spring JDBC (JdbcTemplate, JdbcClient, NamedParameterJdbcTemplate)
- Apply best practices for Spring JDBC data access in Java code
- Detect and fix SQL injection risks in JDBC code
- Improve transaction boundaries or exception handling for JDBC operations

## Workflow

1. **Read reference and assess project context**

Read `references/311-frameworks-spring-jdbc.md` and inspect the current project setup before proposing changes.

2. **Gather scope and decide target improvements**

Identify requested outcomes, constraints, and the minimum safe set of changes to apply.

3. **Apply framework-aligned changes**

Implement or refactor configuration/code following the reference patterns and project conventions.

4. **Run verification and report results**

Execute appropriate build/tests and summarize what changed, what was verified, and any follow-up actions.

## Reference

For detailed guidance, examples, and constraints, see [references/311-frameworks-spring-jdbc.md](references/311-frameworks-spring-jdbc.md).