[jboss-user] [EJB 3.0] - EntityManager auto-flush

[amashtakov]

Hi folks,

I'm trying to figure out how EntityManager flushes pending changes to database, but sticked with one problem - changes are automatically
flushed to database without explicit merge(). Here is a project setup:

1. Entity bean

  | @Entity
  | public class User implements java.io.Serializable {
  | 	private Integer id;
  | 	private String name;
  | 	
  | 	@Id
  | 	@GeneratedValue
  | 	public Integer getId() {
  | 		return id;
  | 	}
  | 	
  | 	public void setId(Integer id) {
  | 		this.id = id;
  | 	}
  | 	public String getName() {
  | 		return name;
  | 	}
  | 	public void setName(String name) {
  | 		this.name = name;
  | 	}
  | }
  | 

2. Stateless bean

  | @Local
  | public interface UserMgrLocal {
  | 	public User findById(Integer id);
  |         ...
  | }
  | 
  | public class UserMgr implements UserMgrLocal {
  | 	@PersistenceContext
  | 	EntityManager em;
  | 
  | 	public User findById(Integer id) {
  | 		System.out.println("invoking findById ...");
  | 		return em.find(User.class, id);
  | 	}
  |         ...
  | }
  | 

3. Page bean (jsf action)

  |         ...
  |         public String notSave() {
  |              System.out.println("BEGIN notSave");
  |              UserManagerLocal userMgr = ... // obtained by JNDI lookup
  |              User u = userMgr.findById(User.class, 1); 
  |              u.setName("kuku"); // no userMgr.save() call !!!
  |              System.out.println("END notSave");
  |              return null;
  |         }
  |         ...
  | 

4. Traces

  | 2008-03-31 11:55:28,292 INFO  [org.domain.Seam1.PageBean1] BEGIN notSave
  | 2008-03-31 11:55:28,292 INFO  [STDOUT] invoking findById ...
  | 2008-03-31 11:55:28,292 DEBUG [org.hibernate.impl.SessionImpl] opened session at timestamp: 4943682471084032
  | 2008-03-31 11:55:28,292 DEBUG [org.hibernate.ejb.AbstractEntityManagerImpl] Looking for a JTA transaction to join
  | 2008-03-31 11:55:28,292 DEBUG [org.hibernate.jdbc.JDBCContext] successfully registered Synchronization
  | 2008-03-31 11:55:28,292 DEBUG [org.hibernate.ejb.AbstractEntityManagerImpl] Looking for a JTA transaction to join
  | 2008-03-31 11:55:28,292 DEBUG [org.hibernate.ejb.AbstractEntityManagerImpl] Transaction already joined
  | 2008-03-31 11:55:28,292 DEBUG [org.hibernate.loader.Loader] loading entity: [org.domain.Seam1.entity.User#1]
  | 2008-03-31 11:55:28,292 DEBUG [org.hibernate.jdbc.AbstractBatcher] about to open PreparedStatement (open PreparedStatements: 0, globally: 0)
  | 2008-03-31 11:55:28,292 DEBUG [org.hibernate.jdbc.ConnectionManager] opening JDBC connection
  | 2008-03-31 11:55:28,292 DEBUG [org.hibernate.SQL] 
  |     select
  |         user0_.id as id4_0_,
  |         user0_.name as name4_0_ 
  |     from
  |         User user0_ 
  |     where
  |         user0_.id=?
  | 2008-03-31 11:55:28,292 DEBUG [org.hibernate.jdbc.AbstractBatcher] about to open ResultSet (open ResultSets: 0, globally: 0)
  | 2008-03-31 11:55:28,292 DEBUG [org.hibernate.loader.Loader] result row: EntityKey[org.domain.Seam1.entity.User#1]
  | 2008-03-31 11:55:28,292 DEBUG [org.hibernate.jdbc.AbstractBatcher] about to close ResultSet (open ResultSets: 1, globally: 1)
  | 2008-03-31 11:55:28,292 DEBUG [org.hibernate.jdbc.AbstractBatcher] about to close PreparedStatement (open PreparedStatements: 1, globally: 1)
  | 2008-03-31 11:55:28,292 DEBUG [org.hibernate.jdbc.ConnectionManager] aggressively releasing JDBC connection
  | 2008-03-31 11:55:28,292 DEBUG [org.hibernate.jdbc.ConnectionManager] releasing JDBC connection [ (open PreparedStatements: 0, globally: 0) (open ResultSets: 0, globally: 0)]
  | 2008-03-31 11:55:28,292 DEBUG [org.hibernate.engine.TwoPhaseLoad] resolving associations for [org.domain.Seam1.entity.User#1]
  | 2008-03-31 11:55:28,292 DEBUG [org.hibernate.engine.TwoPhaseLoad] done materializing entity [org.domain.Seam1.entity.User#1]
  | 2008-03-31 11:55:28,292 DEBUG [org.hibernate.engine.StatefulPersistenceContext] initializing non-lazy collections
  | 2008-03-31 11:55:28,292 DEBUG [org.hibernate.loader.Loader] done entity load
  | 2008-03-31 11:55:28,292 INFO  [org.domain.Seam1.PageBean1] END notSave
  | 2008-03-31 11:55:28,292 DEBUG [org.hibernate.event.def.AbstractFlushingEventListener] processing flush-time cascades
  | 2008-03-31 11:55:28,292 DEBUG [org.hibernate.event.def.AbstractFlushingEventListener] dirty checking collections
  | 2008-03-31 11:55:28,323 DEBUG [org.hibernate.event.def.AbstractFlushingEventListener] Flushed: 0 insertions, 1 updates, 0 deletions to 1 objects
  | 2008-03-31 11:55:28,323 DEBUG [org.hibernate.event.def.AbstractFlushingEventListener] Flushed: 0 (re)creations, 0 updates, 0 removals to 0 collections
  | 2008-03-31 11:55:28,323 DEBUG [org.hibernate.pretty.Printer] listing entities:
  | 2008-03-31 11:55:28,323 DEBUG [org.hibernate.pretty.Printer] org.domain.Seam1.entity.User{name=kuku, id=1}
  | 2008-03-31 11:55:28,323 DEBUG [org.hibernate.jdbc.AbstractBatcher] about to open PreparedStatement (open PreparedStatements: 0, globally: 0)
  | 2008-03-31 11:55:28,323 DEBUG [org.hibernate.jdbc.ConnectionManager] opening JDBC connection
  | 2008-03-31 11:55:28,323 DEBUG [org.hibernate.SQL] 
  |     update
  |         User 
  |     set
  |         name=? 
  |     where
  |         id=?
  | 2008-03-31 11:55:28,339 DEBUG [org.hibernate.jdbc.AbstractBatcher] Executing batch size: 1
  | 2008-03-31 11:55:28,339 DEBUG [org.hibernate.jdbc.AbstractBatcher] about to close PreparedStatement (open PreparedStatements: 1, globally: 1)
  | 2008-03-31 11:55:28,339 DEBUG [org.hibernate.jdbc.ConnectionManager] skipping aggressive-release due to flush cycle
  | 2008-03-31 11:55:28,339 DEBUG [org.hibernate.jdbc.ConnectionManager] aggressively releasing JDBC connection
  | 2008-03-31 11:55:28,339 DEBUG [org.hibernate.jdbc.ConnectionManager] releasing JDBC connection [ (open PreparedStatements: 0, globally: 0) (open ResultSets: 0, globally: 0)]
  | 2008-03-31 11:55:28,339 DEBUG [org.jboss.ejb3.entity.ManagedEntityManagerFactory] ************** closing entity managersession **************
  | 

Applying @TransactionAttribute(NOT_SUPPORTED) to UserMgr bean 
changes behaivour to desired (changes are not applied to database).
As I understant, the persitence context is scoped to transaction
(by default for SLSB) and hibernate EM perform flush on commit,
BUT IMO after the execution of userMgr.findById() the transaction
should be commited and changes shouldn't be applied to database.

Can somebody explain why does this happen ? 

Regards,
/Alexander





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