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Re: [eclipselink-users] Filtering OneToMany and ManyToOne relationship mappings
Hi Tom,

Based on your suggestions i have created my own annotation to declare the foreign key filter i need to apply to that case, so i have something like this:

ManyToOne(cascade=ALL)
@JoinColumn(name="CO_SEQ_NOTIFICATION", referencedColumnName="CO_NOTIFICATION", insertable=false, updatable=false)
@HarmTypeJoin(value=LABORATORY_INFO)
private HarmParameter information;

@OneToMany(cascade=ALL)
@JoinColumn(name = "CO_NOTIFICATION")
@HarmTypeJoin(value=LABORATORY_EXAM)
private Set<HarmParameter> exams;


So this awkward brings either a collection or a single value, depending on the criteria i add to the query based on the Customizer i applied.

My problem now, is how to force a ManyToOne relationship to update the referencedColumnName on persist. Is there a way? Of course this is automatic for the OneToMany mapping.

Thanks


2013/6/4 Tom Ware <tom.ware@xxxxxxxxxx>
Comments inline:


On 03/06/2013 7:33 PM, Luciano Santos wrote:
Hello Tom.

Thanks for the response. I got how it works. Perfect flexibility to be able to
express the additional criterion as JPA-QL or SQL Expressions.

Please feel free to enter an enhancement request for this item and vote for it.  With enough votes we would consider implementing more direct JPA configuration for this feature.



I'll create a base DescriptionCustomizer implementation and reuse it for the
occurrences. Although i am thinking a good way to spread this into code, because
i have about 45 occurences of scalar references to UserRole (Not really
UserRole, was just an example), and other 50 to Sets of UserRole. So i am
thinking of creating a custom annotation such as
@UserRoleFilter(holeType="STANDARD") and add into mapping.

Will i be able to access the declaring Column from the DescriptionCustomizer
somehow so i can grab the annotation data?

It is not clear to me what you mean when you say declaring column but...

A DescriptorCustomizer has access to a ClassDescriptor which has all the information about how a particular Entity is mapped, including, not only, all the information about all the mappings, but also information about the table it is mapped too, caching etc...  If the information is used by JPA it is there. If you can explain more precisely what you are looking for, I can give you a pointer.




If you think it's a good approach, would i be too pretentious about creating a
processor for this custom annotation so we don't need to create a bunch of
DescriptorCustomizer extensions and have to declare them individually on the
classes containing UserRole relationship occurences?

The challenge here is getting the DescriptorCustomizer applied before the persistence unit is initialized.  In a non-Java-EE environment that should be fairly easy to manage because you have control over when the PersistenceUnit is accessed.  In Java EE, it will be more of a challenge since the container will typically initialize the persistence units as they are deployed.

-Tom


Thanks

Luciano G Santos



2013/6/3 Tom Ware <tom.ware@xxxxxxxxxx <mailto:tom.ware@xxxxxxxxxx>>


    Hi Luciano,

       Filtering relationships in EclipseLink requires the use of our native
    API. The way you do it is to create a DescriptorCustomizer

    http://www.eclipse.org/__eclipselink/documentation/2.4/__jpa/extensions/a_customizer.__htm#CHDCCDGC

    <http://www.eclipse.org/eclipselink/documentation/2.4/jpa/extensions/a_customizer.htm#CHDCCDGC>

       In the DescriptorCustomizer, you will have to access the mapping you want
    to change.  Then you will have to alter the selection criteria for the
    mapping. Here is some rough code from our test framework:

       OneToOneMapping _oneToOneMapping_ =
    (OneToOneMapping)descriptor.__getMappingForAttributeName("__computer");
       _expression_ exp = oneToOneMapping.__buildSelectionCriteria();

       ExpressionBuilder builder = exp.getBuilder();
       _expression_ addedExpression =
    builder.getField("MAP_HRW.EMP___LNAME").equal("Louis");
       oneToOneMapping.__setSelectionCriteria(exp.and(__addedExpression));


       Hopefully that will get you started.  If you have problems, we can help
    you on this list.

    -Tom


    On 03/06/2013 11:49 AM, Luciano Santos wrote:

        Hello.

        I am about to change our project's JPA implementation from Hibernate to
        EclipseLink.
        There is a tough relationship i am struggling to accomplish.

        The case is similar as this (as much it might seems to make no much sense):

        @Entity @Table(name="tb_role")
        class Role {
            @Id
            private Long id;

            @Enumerated(STRING)
            private ProductType productType; // STANDARD, SPECIAL
            ...
        }

        @Entity @Table(name="rl_user_role")
        class UserRole {
              ...
             @ManyToOne
             private Role role;

             private String comments;
             ...
        }

        @Entity @Table(name="tb_user")
        class User {
               @Id
               private Long id;

               @ManyToOne
               // NEED to filter for SPECIAL (property or column value on Role)
               // DO NOT HAVE A LOCAL FK column, should use USER_ID on rl_user_role
               private UserRole claimForOthersRole;

               @OneToMany
               // NEED to filter for STANDARD (property or column value on Role)
               @JoinColumn(name = "user_id")

               private Set<UserRole> roles;

        }


        Do you guys have any clue on how could i accomplish this? I was trying
        to use
        Hibernate's @Where annotation, but i could just filter using columns on
        "rl_user_role" (Couldn't be nested).

        Thank you

        Luciano Santos


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