Relation needed on demand while using lazy loading in hibernate

Question

I have project where all the models relations (either 1:m or 1:1) fetch types are defined as lazy. Now consider I have a model called M that has three relation a,b and c and all are 1:m. Now I have three services: Service-A Service-B Service-C

If Service-A return model M then its relation a must be populated although other b,c contains proxy model. If Service-B return model M then its relation b must be populated although other a,c contains proxy model. same as for Service-C

Can anyone know how to accomplished that ?

Another scenario here if there is only one Service and user provide as parameter to load relation a or b or c then how to accomplish that ?

You could look at using the Entity Graph functionality introduced in JPA 2.1 (Hibernate versions 4.3+ I think). See here for further info. thoughts-on-java.org/jpa-21-entity-graph-part-1-named-entity — Alan Hay
– Alan Hay, Commented Dec 15, 2016 at 13:29

Peter Šály · Accepted Answer · 2016-12-20 11:05:55Z

1

Simplest way is to populate them inside transaction:

in ServiceA entity.getCollectionB().size()

in ServiceB entity.getCollectionC().size()

See other ways: http://www.thoughts-on-java.org/5-ways-to-initialize-lazy-relations-and-when-to-use-them/

EDIT: Lazy loading of one to one relation won't work with entity graph either. With or without it you will need bytecode instrumentation. Optimizing columns read is not so important as optimizing row reads. See: http://www.thoughts-on-java.org/jpa-21-entity-graph-part-1-named-entity/#comment-219

edited Dec 20, 2016 at 11:05

answered Dec 16, 2016 at 8:48

Peter Šály

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3 Comments

Asad Khan Over a year ago

Alan hay gives me the best solution.

Asad Khan Over a year ago

This created [n+1] hibernate issue as well.

Peter Šály Over a year ago

In the link are 5 approaches, suitability differs on use case.

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