Sanity check on FlushMode.MANUAL and persist()

[damianharvey.damianharvey.gmail.com]

I'm having one of those days. Can someone confirm my sanity on this one.

What is the expected behaviour when I have my FlushMode set to MANUAL and I call a persist()? I'm seeing the entity added to the database even though I haven't called a flush() nor reached a method boundary. Is this normal?

I see the expected behaviour updating the entity - ie. the second setName doesn't appear in the database until a flush is called.

Code:

@Transactional
public void test() {
        
        log.info("FLUSH MODE : #0", PersistenceContexts.instance().getFlushMode().toString());
        
        Person p = new Person();
        p.setName("Damian");
        
        entityManager.persist(p);  //appears in db after this
        
        p.setName("Is going crazy");  //this won't appear until the flush
        
        log.info("At method boundary");
}

public void flush() {
        entityManager.flush();
}

Cheers,

Damian.

[christian.bauer]

Difference between pre- and post-INSERT id generators. There are books about it.

[damianharvey.damianharvey.gmail.com]

Thanks Christian. I have your book and chapter 11.2.3 was very helpful. I see your point about pre and post-INSERT ID generators.

I am using GenerationType.IDENTITY which is forcing the insert so that Hibernate can get the ID.

As I see it I now have 3 options that are discussed in that chapter:

1. Change my GenerationType to something like SEQUENCE or TABLE. However MySQL doesn't support SEQUENCE.


2. Follow the JPA approach and perform the insert outside of a transaction (which just seems odd)


3. Use Compensation actions to undo what has been inserted to this point.

For my use case option 3 will be the easiest to implement.

Cheers,

Damian.

[aaragus.sibeon.gmail.com]

Hello there,

The solution we found here was to use the evict(obj) option that comes with the Hibernate Session.

Try it out

Darryl A. Sibeon

[christian.bauer]

Look at how the wiki software uses a fake-sequence generator on MySQL, which is a relatively new Hibernate feature. You definitely want pre-INSERT identifier generators wherever you are.

[mokua]

My Link

[damianharvey.damianharvey.gmail.com]

Thanks, that works a treat.

Is the best practice here to use the SequenceStyleGenerator with one common record for all Entities (as per the Seam Wiki) or to maybe use the TableGenerator with a row for each entity? Are there advantages/disadvantages of each approach? With over 100 entities I'm leaning toward the TableGenerator.

For anyone finding this thread later I have changed the ID of my test entity from:

@Id
@GeneratedValue(strategy = IDENTITY)
@Column(name = "ID", unique = true, nullable = false)
public Long getId() {
        return this.id;
}

to

@Id
@GenericGenerator(
                name = "personSequenceGenerator",
                strategy = "org.hibernate.id.enhanced.SequenceStyleGenerator",
                parameters = {
                        @Parameter(name = "sequence_name", value = "PERSON_SEQUENCE"),
                        @Parameter(name = "initial_value", value = "1000"),
                        @Parameter(name = "increment_size", value = "1")
                }
        )
@GeneratedValue(generator = "personSequenceGenerator")
@Column(name = "ID", unique = true, nullable = false)
public Long getId() {
        return this.id;
}

And created a table called PERSON_SEQUENCE with one field called next_val.

Cheers,

Damian