JDBC Database Connectivity

JDBC standardizes relational database access. Prefer a configured pooled DataSource; close connections, statements, and result sets with try-with-resources.

Parameters and transactions

String sql = "select name from users where id = ?";
try (Connection connection = dataSource.getConnection();
     PreparedStatement statement = connection.prepareStatement(sql)) {
    statement.setLong(1, id);
    try (ResultSet rows = statement.executeQuery()) {
        if (rows.next()) return rows.getString("name");
    }
}

Prepared statements separate values from SQL and prevent injection. For multi-step work, disable auto-commit, commit success, and roll back failure. Define isolation, timeouts, batch behavior, null mapping, and generated-key handling. Never share a Connection across concurrent operations unless explicitly supported.