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Replies:
3
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Last Post:
Oct 12, 2006 2:00 PM
by: sbalmos
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Lazy fetching useless with SOAP?
Posted:
Oct 11, 2006 8:17 PM
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Hi all,
This is more of an architectural question... Apparently lazy fetching of an entity's relationships and collections is completely useless with SOAP, because the JAXB XML marshaller touches each of the entity's properties, and thus causing a lazy fetch.
I was somewhat hoping that entities with lazy-fetching properties or collections would, somehow, just return the entity IDs of the entity / collection member entities. I have other explicit methods for retrieving those other member entities, given entity IDs.
But since every property is touched, it's like everything is eagerly fetched. This can *easily* get out of control in my envisioned system, where hundreds of collection members can have parents that have hundreds of other members, etc etc etc. The classic parent/child tree problem which lazy fetching was supposed to solve.
I'm wondering if anyone has any idea on how to rearchitect this. :/
Thanks!
--Scott
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Re: Lazy fetching useless with SOAP?
Posted:
Oct 12, 2006 8:52 AM
in response to: sbalmos
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Hello Scott,
Not sure why the marshaller is touching everything, but two ways out I can see are:
1)Use property based access. This will prevent accessing the attributes directly from causing them to load.
2)The other solution would be to not map relationships at all. Instead, you can map foreign keys as basic mappings, and use these values to lookup the referenced entity.
Best Regards,
Chris
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Re: Lazy fetching useless with SOAP?
Posted:
Oct 12, 2006 10:14 AM
in response to: sbalmos
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I've handled this by creating a business facade for my SOAP calls that all return a set of DTO's that aren't my full entities. I wrote a class to map the entities to the DTO's, and then I marshall the DTO's back to the client.
The app I had designed this way had a web-based front end and a thick client. The thick client used the special facade with limited DTO's (it had a totally different set of functionality than the web UI) and the web UI relied on my standard facade and entity beans.
Hope this helps,
Rob
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Re: Lazy fetching useless with SOAP?
Posted:
Oct 12, 2006 2:00 PM
in response to: robdaemon
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Hi Rob,
That was my first thought, painful as it was. However, I just got this solved with Kohsuke (from the JAXB realm) over in the JAXB forum.
http://forums.java.net/jive/thread.jspa?messageID=162557𧫽
See his blog entry on XML attribute pairs. These work like a charm directly in the entities themselves. I'll post up some quick sample code when I get home from work later today.
This works if you're like me, where you have entities (or collections of such) as return values, but entity *IDs* or collections of such (not entities themselves) as incoming method parameters. If you did that, I guess you could have some logic in the setter that turns around to your DAO layer and... well... looks itself up from the persistence engine? That seems like an entity / DAO abstraction violation in the making.
Anyway... See if that might help you also.
--Scott
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