To correctly handle JDBC transactions, you must first turn off the automatic commit mode, then perform multiple operations, and finally commit or rollback according to the results; 1. Call conn.setAutoCommit(false) to start the transaction; 2. Execute multiple SQL operations, such as INSERT and UPDATE; 3. Call conn.commit() if all operations are successful, and call conn.rollback() if an exception occurs to ensure data consistency; at the same time, try-with-resources should be used to manage resources, properly handle exceptions and close connections to avoid connection leakage; in addition, it is recommended to use connection pools and set save points to achieve partial rollback, and keep transactions as short as possible to improve performance.

Handling transactions in Java with JDBC is essential when you need to ensure data consistency across multiple database operations. By default, JDBC runs in auto-commit mode, meaning each SQL statement is treated as a separate transaction and committed immediately. To manage transactions manually — for example, when you want several operations to succeed or fail together — you need to disable auto-commit and explicitly control when to commit or roll back.

Here's how to properly handle transactions using JDBC:

1. Disable Auto-Commit Mode

Before starting your transaction, turn off auto-commit so that multiple operations can be grouped together:

 Connection conn = dataSource.getConnection();
conn.setAutoCommit(false);

Once disabled, no changes will be saved to the database until you call commit() .

2. Execute Multiple Operations

Now you can execute multiple SQL statements (INSERT, UPDATE, DELETE, etc.) as part of the same transaction:

 try (PreparedStatement ps1 = conn.prepareStatement("INSERT INTO accounts (id, balance) VALUES (?, ?)")) {
    ps1.setInt(1, 1001);
    ps1.setDouble(2, 500.0);
    ps1.executeUpdate();
}

try (PreparedStatement ps2 = conn.prepareStatement("UPDATE accounts SET balance = balance - ? WHERE id = ?")) {
    ps2.setDouble(1, 200.0);
    ps2.setInt(2, 1000);
    ps2.executeUpdate();
}

These operations won't be visible to other transactions until committed.

3. Commit or Roll Back Based on Outcome

After all operations, if everything succeeded, call commit() :

 conn.commit();

If any exception occurs, roll back the entire transaction to maintain consistency:

 try {
    // ... your JDBC operations
    conn.commit();
} catch (SQLException e) {
    try {
        conn.rollback();
    } catch (SQLException ex) {
        ex.printStackTrace();
    }
    throw e;
}

Always wrap the rollback in a try-catch block because it can also throw an exception.

4. Use Try-With-Resources and Proper Exception Handling

To ensure resources are closed and connections are not leaked, use try-with-resources and handle exceptions carefully:

 Connection conn = null;
try {
    conn = dataSource.getConnection();
    conn.setAutoCommit(false);

    // Perform DB operations
    try (PreparedStatement ps1 = conn.prepareStatement("INSERT INTO logs (msg) VALUES (?)")) {
        ps1.setString(1, "Transaction started");
        ps1.executeUpdate();
    }

    try (PreparedStatement ps2 = conn.prepareStatement("UPDATE accounts SET balance = ? WHERE id = ?")) {
        ps2.setDouble(1, 1000.0);
        ps2.setInt(2, 1001);
        ps2.executeUpdate();
    }

    conn.commit();
} catch (SQLException e) {
    if (conn != null) {
        try {
            conn.rollback();
        } catch (SQLException ex) {
            ex.printStackTrace();
        }
    }
    e.printStackTrace();
} finally {
    if (conn != null) {
        try {
            conn.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

Best Practices

• Always rollback on error : Never leave a transaction open after an exception.
• Keep transactions short : Long-running transactions can lock resources and hurt performance.
• Use connection pooling in production : Tools like HikariCP help manage connections efficiently.
• Avoid catching and swallowing exceptions : Make sure errors don't prevent rollback.
• Consider savepoints for partial rollbacks (advanced use case):

 Savepoint sp = conn.setSavepoint("before_risky_operation");
// ... risky operation
// If something goes wrong:
conn.rollback(sp);

Basically, handling transactions in JDBC comes down to three key steps: disable auto-commit, group your operations, then commit or rollback based on success. It's simple but easy to get wrong if you don't handle exceptions and cleanup properly.

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