15.19. Polymorphism

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HQL and JPQL queries are inherently polymorphic.

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<pre class="prettyprint highlight">`List&lt;Payment&gt; payments = entityManager.createQuery(
    "select p " +
    "from Payment p ", Payment.class )
.getResultList();`</pre>
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This query names the `Payment` entity explicitly.
However, all subclasses of `Payment` are also available to the query.
So if the `CreditCardPayment` and `WireTransferPayment` entities extend the `Payment` class, all three types would be available to the entity query,
and the query would return instances of all three.

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This can be altered by using either the `org.hibernate.annotations.Polymorphism` annotation (global, and Hibernate-specific) or limiting them using in the query itself using an entity type expression.

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The HQL query `from java.lang.Object` is totally valid! It returns every object of every type defined in your application.

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