Hibernate Lazy Loading Single Column

Question

Using Spring running in Tomcat and Hibernate 5.0

Trying to lazy load a single column, which doesn't seem to be supported without bytecode enhancement. I've attempted following these steps but the column is still being loaded as the initial query.

@Bean( JpaConfig.EMF )
public LocalContainerEntityManagerFactoryBean entityManagerFactory(
final DataSource dataSource,
final JpaVendorAdapter jpaVendorAdapter )
....
props.put( AvailableSettings.ENHANCER_ENABLE_LAZY_INITIALIZATION, Boolean.toString( true ) );
emf.setJpaPropertyMap( props );

Column Config

@Column( name = "file_data", nullable = false )
@Basic( fetch = FetchType.LAZY )
    private byte[] fileData;

Spring Configuration class

@Configuration
@EnableLoadTimeWeaving

Startup Output

[INFO ] [17:22:56] [localhost-startStop-1] weaving.DefaultContextLoadTimeWeaver:76 - Determined server-specific load-time weaver: org.springframework.instrument.classloading.tomcat.TomcatLoadTimeWeaver
Jun 12, 2018 5:22:56 PM org.apache.catalina.loader.WebappClassLoaderBase addTransformer
INFO: Added class file transformer [org.springframework.context.weaving.AspectJWeavingEnabler$AspectJClassBypassingClassFileTransformer@6086a542] to web application [ROOT].
[INFO ] [17:22:56] [localhost-startStop-1] weaving.DefaultContextLoadTimeWeaver:76 - Determined server-specific load-time weaver: org.springframework.instrument.classloading.tomcat.TomcatLoadTimeWeaver
[INFO ] [17:27:05] [localhost-startStop-1] jpa.LocalContainerEntityManagerFactoryBean:356 - Building JPA container EntityManagerFactory for persistence unit 'persistenceUnit'
Jun 12, 2018 5:27:20 PM org.apache.catalina.loader.WebappClassLoaderBase addTransformer
INFO: Added class file transformer [Standard ClassFileTransformer wrapping JPA transformer: org.hibernate.jpa.internal.enhance.EnhancingClassTransformerImpl@20635e8] to web application [ROOT].

Am I missing something?

fg78nc · Accepted Answer · 2018-06-12 20:54:18Z

1

According to JPA specifications directive to load lazily is only a hint to the persistence provider, Hibernate, in your case. The provider may not respect your hint. In general, what is your objective? You don't loose much in fetching additional field of basic type, as there is no object graph involved. If you have large array, add @Lob annotation.

answered Jun 12, 2018 at 20:54

fg78nc

5,2624 gold badges24 silver badges38 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Evan L Over a year ago

The array is large, I'm not sure what @Lob gains me, it doesn't appear to affect the Laziness. The fileData is always populated, but we only want to load the data when someone wants to view the contents of the file. We pull a Collection of these Objects to present to the user, then if they wish to view the contents they click and that's when we want data to load.

fg78nc Over a year ago

What is the type of filedata on your database side?

Evan L Over a year ago

It's a BLOB, so I can see how the @Lob annotation is appropriate. I just don't know how it helps with my need of Lazy loading.

fg78nc Over a year ago

If it's BLOB they all Hibernate will fetch is location_id, not the data itself.

Collectives™ on Stack Overflow

Hibernate Lazy Loading Single Column

1 Answer 1

4 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related