Web site management - Transaction essentials 10.1.3 Transactions with Java Persistence With
Transaction essentials 10.1.3 Transactions with Java Persistence With Java Persistence, you also have the design choice to make between programmatic transaction demarcation in application code or declarative transaction demarcation handled automatically by the runtime container. Let s investigate the first option with plain Java SE and then repeat the examples with JTA and EJB components. The description resource-local transaction applies to all transactions that are controlled by the application (programmatic) and that aren t participating in a global system transaction. They translate directly into the native transaction system of the resource you re dealing with. Because you re working with JDBC databases, this means a resource-local transaction translates into a JDBC database transaction. Resource-local transactions in JPA are controlled with the EntityTransaction API. This interface exists not for portability reasons, but to enable particular features of Java Persistence for instance, flushing of the underlying persistence context when you commit a transaction. You ve seen the standard idiom of Java Persistence in Java SE many times. Here it is again with exception handling: EntityManager em = null; EntityTransaction tx = null; try { em = emf.createEntityManager(); tx = em.getTransaction(); tx.begin(); concludeAuction(em); tx.commit(); } catch (RuntimeException ex) { try { tx.rollback(); } catch (RuntimeException rbEx) { log.error(”Couldn’t roll back transaction”, rbEx); } throw ex; } finally { em.close(); } This pattern is close to its Hibernate equivalent, with the same implications: You have to manually begin and end a database transaction, and you must guarantee that the application-managed EntityManager is closed in a finally block. (Although we often show code examples that don t handle exceptions or are wrapped in a try/catch block, this isn t optional.)
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