What requirements are imposed on transactions in software development?

Transactions must satisfy the ACID properties:

• Atomicity: A transaction must be either fully completed or fully rolled back. If any part of the transaction fails, the entire transaction is reverted to its initial state.
• Consistency: A transaction transitions the database from one consistent state to another. It should not violate data integrity or constraint rules.
• Isolation: Concurrent transactions should not affect each other. The outcome of executing multiple transactions should be the same as if they were executed sequentially. Isolation issues include:
  • Dirty read: Reading data that has not yet been committed by another transaction.
  • Non-repeatable read: Re-reading the same data within a transaction yields different results because another transaction has modified and committed the data in between.
  • Phantom read: Re-executing a query with a condition within a transaction returns a different set of rows because another transaction has added or removed rows matching the condition.
• Durability: Once a transaction is successfully completed (committed), the changes it made should be permanent and withstand system failures (e.g., power outages).

In Java, frameworks like Spring Framework with its declarative transaction management (@Transactional) or Java Transaction API (JTA) are often used to manage transactions.

Example of using @Transactional:

@Transactional  
public void processOrder(Order order) {  
    // Order processing logic  
    // For example, debiting funds from an account  
    accountService.debit(order.getCustomerId(), order.getAmount());  

    // Updating order status  
    orderRepository.updateStatus(order.getId(), "Processed");  

    // In case of an error (e.g., insufficient funds)  
    // the entire transaction will be rolled back automatically,  
    // unless specified otherwise (@Transactional(noRollbackFor = ...))  
}