Chapter 5. Managing JTA transactions programmatically using the API approach

Procedure

1. Inject the UserTransaction interface:

   src/main/java/org/acme/SantaClauseService.java

   @ApplicationScoped
   public class SantaClausService {
   
       @Inject ChildDAO childDAO;
       @Inject SantaClausDAO santaDAO;
       @Inject UserTransaction transaction;
   }

2. Use the transaction demarcation methods to control the transaction:

   src/main/java/org/acme/SantaClauseService.java

   import javax.transaction.Transactional;
   import javax.inject.Inject;
   import javax.transaction.SystemException;
   import javax.transaction.UserTransaction;
   
   @ApplicationScoped
   public class SantaClausService {
   
       @Inject ChildDAO childDAO;
       @Inject SantaClausDAO santaDAO;
       @Inject UserTransaction transaction;
   
       public void getAGiftFromSanta(Child child, String giftDescription) {
           // some transaction work
           try {
               transaction.begin(); 

   1

   
               Gift gift = childDAO.addToGiftList(child, giftDescription);
               santaDAO.addToSantaTodoList(gift);
               transaction.commit();
           }
           catch(SomeException e) {
               // do something on Tx failure
               transaction.rollback(); 

   2

   
           }
       }
   }

   1

   Place your transaction code between the transaction.begin() and the transaction.commit().

   2

   Aborts the transaction immediately.

   Note

   You cannot use UserTransaction in a method where a transaction starts by a @Transactional call.

Procedure

1. Inject the TransactionManager and set the transaction for rollback with setRollbackOnly:

   In this example, the transaction context is propagated to all calls nested in the @Transactional method (childDAO.addToGiftList() and santaDAO.addToSantaTodoList()). The transaction manager commits the transaction unless a runtime exception crosses the method boundary.

   Example src/main/java/org/acme/SantaClausService.java

   import javax.transaction.Transactional;
   import javax.inject.Inject;
   import javax.transaction.SystemException;
   import javax.transaction.UserTransaction;
   
   @ApplicationScoped
   public class SantaClausService {
   
       @Inject TransactionManager tm; 

   1

   
       @Inject ChildDAO childDAO;
       @Inject SantaClausDAO santaDAO;
   
       @Transactional
       public void getAGiftFromSanta(Child child, String giftDescription) {
           // some transaction work
           Gift gift = childDAO.addToGiftList(child, giftDescription);
           if (gift == null) {
               tm.setRollbackOnly(); 

   2

   
           }
           else {
               santaDAO.addToSantaTodoList(gift);
           }
       }
   }

   1

   Inject the TransactionManager to be able to activate setRollbackOnly semantic.

   2

   Programmatically decide when to roll back the transaction.