spring-jdbc-template

Raw JDBC requires manually managing every step of database access: getting a connection, creating a statement, setting parameters, iterating a ResultSet, handling checked SQLExceptions, and closing resources in finally blocks. A simple query becomes 15+ lines of repetitive, error-prone boilerplate.

Spring JDBC Template provides a template-based API that eliminates JDBC boilerplate. JdbcTemplate wraps the JDBC workflow: it handles connection acquisition, statement creation, parameter binding, result extraction, and cleanup. Developers provide only the SQL and the logic to map results to objects.

1. JdbcTemplate: Core class wrapping JDBC — execute query/update with automatic resource management
2. NamedParameterJdbcTemplate: Uses named parameters (:name) instead of positional (?) — more readable, especially with many parameters
3. RowMapper: (ResultSet rs, int rowNum) → T maps a result set row to a domain object
4. ResultSetExtractor: For custom result extraction (e.g., building a Map from multiple rows)
5. SQL scripts: ResourceDatabasePopulator or ScriptUtils for executing SQL scripts during testing or setup

• JdbcTemplate: Simplest template — positional ? parameters, automatic resource cleanup
• NamedParameterJdbcTemplate: Named :param parameters, better readability, uses SqlParameterSource
• SimpleJdbcTemplate (deprecated): Legacy wrapper, replaced by JdbcTemplate
• RowMapper: Maps individual rows — reusable, no external state
• ResultSetExtractor: Processes entire ResultSet (multiple rows, custom structures)
• SQL scripts: Execute SQL files via ResourceDatabasePopulator for setup, testing, or migrations
• PreparedStatementCallback: For full control over PreparedStatement creation and execution

• Built from: JDBC — JdbcTemplate is a wrapper over raw JDBC
• Built from: Spring Framework — JdbcTemplate is a Spring module for data access
• Contrasts with: Spring ORM — JdbcTemplate is direct SQL; Spring ORM is object-oriented
• Contrasts with: Spring Data JPA — JdbcTemplate gives SQL control; JPA abstracts SQL
• Related: Hibernate Query Language — Both execute database queries; HQL is ORM-based, JdbcTemplate is SQL-based

• Large results: JdbcTemplate fetches all results into memory by default — use RowCallbackHandler or streaming for large datasets
• No caching: Unlike ORM, JdbcTemplate has no built-in caching — each query hits the database
• No lazy loading: All fields must be explicitly selected; no proxy-based lazy loading
• SQL injection: Always use parameterized queries (? or :param), never concatenate user input into SQL strings
• DataSource configuration: JdbcTemplate needs a properly configured DataSource bean; Spring Boot auto-configures one