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Re: [eclipselink-users] [MOXy] setting bi-directional references during unmarshalling
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Hi Matt,
Thank you for the quick and informative response! :) I am currently using
EL 1.1.2. It sounds like there's a good reason to upgrade to 1.2. I do
have a few more questions though:
1. The example that you described below would work well for 1:many
bi-directional relationships. But what about many:many bi-directional
relationships? For example, if class "A" has a collection of B's, and "B"
has a collection of A's, the code to set the back-reference then looks like:
public void addB(B b) {
this.getBs().add(b);
b.getAs().add(this);
}
}
EL 1.2 can take care of this too?
2. Would the workaround that I have described work? Does EclipseLink need
public getters and setters if I turn on "method access"? Or would
private/protected methods be ok?
Thanks!
--Polly
Matt MacIvor wrote:
>
> Hey Polly,
>
> We're currently working on better support for handling bi-directional
> relationship mappings in EclipseLink. Currently in EclipseLink 1.2
> (which is available today) for containment relationships, you can
> configure the mapping to automatically set the back-reference when it's
> populating the collection. This functionality isn't currently exposed
> in the MappingWorkbench but is available through the mapping APIs,
> Project XML and in JAXB through a custom annotation.
>
> Using the mapping APIs you would do something like:
> XMLCompositeCollectionMapping childMapping = new
> XMLCompositeCollectionMapping();
> childMapping.setXPath("children/child");
> childMapping.setReferenceClass(Child.class);
> //Specify the name of the attribute on the reference class that points
> back to the container object
> childMapping.setContainerAttributeName("parent");
> childMapping.setContainerGetMethodName("getParent");
> childMapping.setContainerSetMethodName("setParent");
> parentDescriptor.addMapping(childMapping);
>
> If you're using Project XML, this can also be specified in the xml
> version of the project using the <container-attribute> element on
> the composite mapping.
>
> In EclipseLink 1.2 this support is only availabe for Containment based
> mappings (XMLCompositeObjectMapping and XMLCompositeCollectionMapping),
> but EclipseLink 2.0 will have expanded support for bi-directional
> relationships to also include reference mappings.
>
> Hope this helps,
>
> -Matt
>
> polly.c.chang wrote:
>
> Hi,
>
> I have a bi-directional relationship between Parent and Child classes like
> this:
>
> public class Parent {
> private List<Child> children;
>
> public List<Child> getChildren()
> public void setChildren(List<Child> children)
> public void addChild(final Child child) {
> this.getChildren().add(child);
> child.setParent(this);
> }
> public void removeChild(final Child child) {
> this.getChildren().remove(child);
> child.setParent(null);
> }
> }
>
> public class Child {
> private Parent parent;
>
> public void setParent(Parent parent)
> public Parent getParent()
> }
>
> When I unmarshal the Parent object, I find that the "children" collection
> contains Child objects that do not have the back-reference to the Parent.
> This is probably because the Child objects were unmarshalled and set
> directly into the "children" collection. How do I change the behavior so
> that EclipseLink MOXy calls the addChild() method for each Child object?
> I
> looked around EclipseLink Workbench and the schema, but I can't find any
> mappings that look suitable. Does MOXy support adding objects into a
> collection by calling an add() method?
>
> If MOXy does not support calling an add() method for unmarshalling
> collections, then the only workaround that I can think of is to turn on
> "method accessing" for each bi-directional collection so that MOXy uses
> the
> getter and setter methods for the list. Then the setter needs to go
> through
> the collection and fix up the back references to the Parent. Usually my
> setter is private/protected, so I assume that I'd have to make it public
> too
> for EclipseLink to use it.
>
> What do you recommend?
>
> Thanks!
> --Polly
>
>
>
>
>
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> eclipselink-users mailing list
> eclipselink-users@xxxxxxxxxxx
> https://dev.eclipse.org/mailman/listinfo/eclipselink-users
>
>
--
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