Spring Boot REST API: How to Handle Concurrent Requests with Atomic Operations?
I'm wondering if anyone has experience with I've searched everywhere and can't find a clear answer. I'm working on a Spring Boot REST API and I've encountered an issue with handling concurrent requests that modify the same resource. My API is designed to manage a simple inventory system where users can update stock quantities. However, when multiple requests to update the stock are processed simultaneously, they occasionally result in incorrect stock counts. For instance, if two requests to add stock to the same item come in at nearly the same time, they might both read the stock quantity as 10, and both could end up setting it to 15, instead of the expected 20. I'm currently using a standard service with the following method to update stock quantities: ```java @Transactional public void updateStock(Long itemId, int quantity) { Item item = itemRepository.findById(itemId).orElseThrow(() -> new ResourceNotFoundException("Item not found")); item.setStock(item.getStock() + quantity); itemRepository.save(item); } ``` To address this, I attempted to use `@Version` for optimistic locking, but I'm still experiencing race conditions. Here's what my entity looks like: ```java @Entity public class Item { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; private String name; private int stock; @Version private Long version; // Getters and Setters } ``` I also considered implementing a synchronized block in my service method, but that seems to defeat the purpose of using a REST service. Instead, I tried using `ReentrantLock`, but it introduces additional complexity and could lead to performance issues under high load. What would be the best way to handle concurrent updates to ensure data integrity without significantly impacting performance? Are there any design patterns or best practices I should consider using in this scenario? This issue appeared after updating to Java stable. Thanks in advance! What am I doing wrong?