JPA/Hibernate query with class name?

Question

In this example com.test.Cat extends com.test.Animal and there is no field DB in CAT table of com.test.Cat explicitly defining its type (it wasn't me).

When I query my animals from DB I get a collection of Animals.

It is possible to sort them by class name:

order by r.class

but is there a way to use class name as a criteria? For example I would like to get all animals expect dogs. But no luck - even this does not work:

where r.class = ?      (String "ccc.test.Cat")

as I get an exception:

Caused by: java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Integer
    at org.hibernate.type.IntegerType.set(IntegerType.java:64)
    at org.hibernate.type.NullableType.nullSafeSet(NullableType.java:154)
    at org.hibernate.type.NullableType.nullSafeSet(NullableType.java:136)
    at org.hibernate.param.PositionalParameterSpecification.bind(PositionalParameterSpecification.java:62)
    at org.hibernate.loader.hql.QueryLoader.bindParameterValues(QueryLoader.java:514)
    at org.hibernate.loader.Loader.prepareQueryStatement(Loader.java:1589)
    at org.hibernate.loader.Loader.doQuery(Loader.java:696)
    at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:259)
    at org.hibernate.loader.Loader.doList(Loader.java:2228)
    at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2125)
    at org.hibernate.loader.Loader.list(Loader.java:2120)
    at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:401)
    at org.hibernate.hql.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:361)
    at org.hibernate.engine.query.HQLQueryPlan.performList(HQLQueryPlan.java:196)
    at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1148)
    at org.hibernate.impl.QueryImpl.list(QueryImpl.java:102)
    at org.hibernate.ejb.QueryImpl.getResultList(QueryImpl.java:67)

Could you post the class and table definitions?

Péter Török
– Péter Török

2010-02-23 11:31:23 +00:00
Commented Feb 23, 2010 at 11:31 — Péter Török
– Péter Török, Commented Feb 23, 2010 at 11:31

Pascal Thivent · Accepted Answer · 2010-02-23 11:57:22Z

6

According to the chapter 14.9 of the documentation, you shouldn't use double quotes:

The special property class accesses the discriminator value of an instance in the case of polymorphic persistence. A Java class name embedded in the where clause will be translated to its discriminator value.
from Cat cat where cat.class = DomesticCat

edited Feb 23, 2010 at 11:57

answered Feb 23, 2010 at 11:45

Pascal Thivent

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2 Comments

Petteri H Over a year ago

Thanks, I fixed the example. The original code used '?' for prepared statement.

Pascal Thivent Over a year ago

@Petteri I just tested this HQL query and it works as expected (without quotes or double quotes). It's not a String that is expected, not sure you can use a prepared statement here (at least not with setString)

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