Spring Framework, Spring Boot, Transactions, Transaction Management, Isolation Level.
Propagation.REQUIRED, isolation = Isolation.READ_COMMITTED) public Product getById(Integer id) { return productRepository.findById(id).orElse(null); } REPEATABLE_READ 3rd level is isolation. Prevents DIRTY READ and NON-REPEATABLE READ. @Transactional(propagation = Propagation.REQUIRED, isolation =