Spring JDBC — JdbcTemplate and JdbcClient

Apply Spring JDBC guidelines using JdbcTemplate, NamedParameterJdbcTemplate, and JdbcClient.

What is covered in this Skill?

• Parameterized SQL (never concatenate user input)
• JdbcClient fluent API for new code (Spring Framework 6.1+)
• NamedParameterJdbcTemplate for named placeholders
• RowMapper and DataClassRowMapper (records)
• Batch operations
• Safe handling of generated keys (KeyHolder / JdbcClient returning keys)
• 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

Reference

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