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@CollectionId on a List. Equals fails. PersistentIdentifier

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ramat123

Post subject: @CollectionId on a List. Equals fails. PersistentIdentifier

Posted: Sun Aug 28, 2011 5:06 pm

Newbie

Joined: Wed Sep 03, 2008 9:56 am
Posts: 6

Hi Users,

I've configured the following List in my Entity:

Code:

    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    @JoinTable(name="KW_TARGET_OPERATION_TEMPLATE_XREF", joinColumns={ @JoinColumn(name = "TARGET_OPERATION_ID") }, inverseJoinColumns={ @JoinColumn(name="TEMPLATE_ID", referencedColumnName="TARGETING_TEMPLATE_ID") })
    @GenericGenerator(name="TARGET_OPERATION_TEMPLATE_XREF_GENERATOR", strategy = "org.hibernate.id.enhanced.SequenceStyleGenerator", parameters = {@Parameter(name = "sequence_name", value = "KOBE_MART_TBLS.KW_TARGET_OPERATION_TEMPLATE__TARGET_OPERATION_TEMPLATE_XRE_SEQ")})
    @CollectionId(columns = @Column(name = "TARGET_OPERATION_TEMPLATE_XREF_ID"), type = @Type(type = "long"), generator = "TARGET_OPERATION_TEMPLATE_XREF_GENERATOR")
    private List<TargetingTemplateVO> templates = new ArrayList<TargetingTemplateVO>();

Now, when implementing a simple equals (with special care for the id) I fail on the templates List as the List returns as a PersistentIdentiferBag which does not override equals..

This looks very common to me but I did not find any blog posting on this.

What am I missing?

Thanks a lot,

David

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ramat123

Post subject: Re: @CollectionId on a List. Equals fails. PersistentIdentifier

Posted: Mon Aug 29, 2011 7:29 am

Newbie

Joined: Wed Sep 03, 2008 9:56 am
Posts: 6

So here is what I was missing when spending a lot of time overcoming this problem.

Hibernate value objects are not pure POJOs as unlike POJO they have a state which means they may be transient (before save them to the database) or persistent (after saving them to the database).

This means that their equals method does not work as the ordinary deep comparison we do with pure POJOs.

For PersistentIdentifierBag a decision was made not to override equals to make sure a calling equals would not fetch an hierarchy and make it an EAGER one.

This means that we should treat Hibernate Objects as database rows. By that I mean that we should compare them by their business keys (lots of stuff about that in documentation but somehow I skipped it). If two object are of the same class and have the same primary key we treat them as same objects.

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