Strange hibernate cache behaviour

Question

I use ehcache and hibernate 3.6.7 Final. This a pseudo code sample that reveals problem with caching.

@Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
public class A{    

    long id;    

    @OneToMany(mappedBy = "aId", targetEntity = B.class, fetch = FetchType.LAZY)
    @Fetch(value = FetchMode.JOIN)
    @Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
    protected Set<B> fieldB;
}    


@Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
public class B { 

    long id;

    long bId; 
}

1) First time when I load entity A from hibernate it does not read fieldB. And this is ok - cause FetchType.LAZY is set.

2) Second time when I load entity A I see sql queries retrieving entity A JOIN entity B.

3)If remove @Fetch(value = FetchMode.JOIN) point 2 will not be performed.

So the question is this bug or feature? And how can I avoid such latent things.

You can try asking also on the Hibernate Forums. And if you are brave enough (and have time), debug using Hibernate source code. — Luciano
– Luciano, Commented Jun 15, 2012 at 12:21

kentonue · Accepted Answer · 2012-06-15 15:56:50Z

1

You have two conflicting fetches, you definitely do not want to specify the fetch on the column and the @Fetch annotation as it will provide unpredicatable behavior.

answered Jun 15, 2012 at 15:56

kentonue

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