How to make value in table computational in database (hibernate)?

Question

I have two tables (A and B): one of table is structure of some object (A) and other table that connected two tables A and table C by many-to-many mapping (B). In table A I have column that must be computed using table B. How can I make this column auto-computing in hibernate?

Main question: how to make column in Hibernate as query?

Upd:

I have tried @Formula annotation and have got org.hibernate.type.SerializationException: could not deserialize.

Do you have some idea about this situation?

The code of this field looks like:

@Formula("(select count(t.first_id) from " + TABLE_NAME + " as t group by t.second_id)")
private int count;

setCount(...);
... getCount();

Stack trace:

org.hibernate.type.SerializationException: could not deserialize
        at org.hibernate.internal.util.SerializationHelper.doDeserialize(SerializationHelper.java:243)
        at org.hibernate.internal.util.SerializationHelper.deserialize(SerializationHelper.java:287)
        at org.hibernate.type.descriptor.java.SerializableTypeDescriptor.fromBytes(SerializableTypeDescriptor.java:138)
        at org.hibernate.type.descriptor.java.SerializableTypeDescriptor.wrap(SerializableTypeDescriptor.java:113)
        at org.hibernate.type.descriptor.java.SerializableTypeDescriptor.wrap(SerializableTypeDescriptor.java:27)
        at org.hibernate.type.descriptor.sql.VarbinaryTypeDescriptor$2.doExtract(VarbinaryTypeDescriptor.java:53)
        at org.hibernate.type.descriptor.sql.BasicExtractor.extract(BasicExtractor.java:47)
        at org.hibernate.type.AbstractStandardBasicType.nullSafeGet(AbstractStandardBasicType.java:241)
        at org.hibernate.type.AbstractStandardBasicType.nullSafeGet(AbstractStandardBasicType.java:237)
        at org.hibernate.type.AbstractStandardBasicType.nullSafeGet(AbstractStandardBasicType.java:227)
        at org.hibernate.type.AbstractStandardBasicType.hydrate(AbstractStandardBasicType.java:303)
        at org.hibernate.persister.entity.AbstractEntityPersister.hydrate(AbstractEntityPersister.java:2726)
        at org.hibernate.loader.Loader.loadFromResultSet(Loader.java:1728)
        at org.hibernate.loader.Loader.instanceNotYetLoaded(Loader.java:1654)
        at org.hibernate.loader.Loader.getRow(Loader.java:1543)
        at org.hibernate.loader.Loader.getRowFromResultSet(Loader.java:727)
        at org.hibernate.loader.Loader.processResultSet(Loader.java:972)
        at org.hibernate.loader.Loader.doQuery(Loader.java:930)
        at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:336)
        at org.hibernate.loader.Loader.doList(Loader.java:2611)
        at org.hibernate.loader.Loader.doList(Loader.java:2594)
        at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2423)
        at org.hibernate.loader.Loader.list(Loader.java:2418)
        at org.hibernate.loader.criteria.CriteriaLoader.list(CriteriaLoader.java:109)
        at org.hibernate.internal.SessionImpl.list(SessionImpl.java:1716)
        at org.hibernate.internal.CriteriaImpl.list(CriteriaImpl.java:363)
        at org.hibernate.internal.CriteriaImpl.uniqueResult(CriteriaImpl.java:385)

StanislavL · Accepted Answer · 2016-03-11 12:46:38Z

1

You can use @Formula annotation and define an Entity field based on computed SQL expression.

@Formula(" select count(*) from C where C.dependent_id=id")
public int expressionCount;

where id is column of table where the Entity is mapped

answered Mar 11, 2016 at 12:46

StanislavL

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2 Comments

Timofey Over a year ago

Thank you for your answer, but I have tried it and have got org.hibernate.type.SerializationException: could not deserialize. Do you have some idea about this situation? The code I put into question.

StanislavL Over a year ago

could be issue with setting annotation on fields and methods stackoverflow.com/questions/13253403/…

dpr · Accepted Answer · 2016-03-11 14:46:35Z

1

Haven't tried it myself but this thread in the hibernate forums pretty much describes the same problem you are encountering with the @Formula annotation.

https://forum.hibernate.org/viewtopic.php?f=1&t=1010737&view=previous

According to the thread'S author changing the computed field's type from int to Long solved the deserialization issue.

answered Mar 11, 2016 at 14:46

dpr

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