Transaction Management

About

In JDBC, transaction management is handled manually by controlling the auto-commit behavior of a Connection object. JDBC transactions allow us to group multiple SQL operations into a single atomic unit of work. If one of the operations fails, we can roll back the entire transaction to maintain data consistency.

1. Basics of JDBC Transactions

By default, JDBC connections operate in auto-commit mode. This means every SQL statement is immediately committed after execution. For proper transaction management, you must disable auto-commit and explicitly commit or roll back the transaction.

Example (without Spring):

Connection conn = dataSource.getConnection();
try {
    conn.setAutoCommit(false); // start transaction

    // Execute multiple SQL statements
    PreparedStatement stmt1 = conn.prepareStatement("INSERT INTO employee ...");
    stmt1.executeUpdate();

    PreparedStatement stmt2 = conn.prepareStatement("UPDATE salary ...");
    stmt2.executeUpdate();

    conn.commit(); // commit if everything succeeds
} catch (SQLException e) {
    conn.rollback(); // rollback on any failure
    throw e;
} finally {
    conn.setAutoCommit(true); // restore default behavior
    conn.close();
}

2. Spring JDBC Transaction Management

Spring provides a higher-level abstraction for managing transactions, often through:

• Declarative approach using @Transactional

• Programmatic approach using TransactionTemplate

Spring will manage the Connection, disable auto-commit, and commit or roll back the transaction based on the method execution and exceptions.

Example (declarative):

@Transactional
public void performTransfer() {
    jdbcTemplate.update("UPDATE account SET balance = balance - 100 WHERE id = 1");
    jdbcTemplate.update("UPDATE account SET balance = balance + 100 WHERE id = 2");
}

In this case:

• Spring will automatically manage the transaction boundaries.

• If any exception is thrown inside the method, the entire transaction will be rolled back.

Important Points

• Auto-commit

  • Enabled by default. Each SQL is committed automatically.

  • Must be set to false to begin a manual transaction.

• Commit

  • Used to make all changes made during the transaction permanent.

• Rollback

  • Used to revert all changes made during the transaction if an error occurs.

• Savepoints

  • We can define intermediate points in a transaction to roll back partially instead of the whole transaction.

  • Example:

    Savepoint savepoint = conn.setSavepoint();
    // do something
    conn.rollback(savepoint); // rollback only to savepoint

Common Mistakes to Avoid

• Not resetting autoCommit to true after transaction ends (can cause issues if connection is reused).

• Not closing the Connection in a finally block (can lead to leaks).

• Assuming database rollback will always happen automatically (some databases require explicit rollback).

When to Use JDBC-level Transactions ?

• When working directly with JDBC or Spring JDBC (JdbcTemplate).

• In small projects without the need for ORM or JPA.

• When we need precise, low-level control over transaction boundaries.

• When using stored procedures, or performing complex batch operations.