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How to get instance of child class, not parent class?  RSS feed

 
Greenhorn
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I have a child class which extends a parent class.

@Entity
public class ChildClass extends ParentClass implements Serializable

When I retrieve the child class (see below), I get an instance of the parent class even though the 1st parameter is the child class:
ChildClass childClass = em.find(ChildClass.class, childClassId);

1. I thought I am supposed to get an instance of the child class, not an instance of the parent class. Can someone explain why this is so?
2. How do I get an instance of the child class?

Thanks,
Lin

 
Bartender
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Hi Lin. Welcome to the Ranch!

Why do you think you aren't getting an instance of the child class? Is it throwing a ClassCastException, or is something else going on?
 
Lin Ahmad
Greenhorn
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Thanks! Matthew. You're right it is throwing a ClassCastException.



Also, the check below produces the child class:


The child class is an association table with two fields: childID and parentID. The parent class has the parentID as the primary key and about 40 other fields. Modifications to these two entity classes are not allowed.

Lin
 
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