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question about primary key in JPA

 
Ranch Hand
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mock question:

Which statement is true about the primary key of a Java Persistence entity?
A. The primary key cannot be overridden by a mapping descriptor.
B. The location of the primary key defines in the topmost entity class in the hierarchy.
C. If property-based access is used, the properties or the primary key class must be public or protected.
D. At least part of a primary key must be defined in the class that is the topmost class of an entity which is defined by a hierarchy of classes.

Given answer is C,primary key could be put in mapped superclass too,so B is wrong,D apparently wrong.
why A is wrong?
can anyone explain C(why property-based,why public or protected,and how about field-based access?)
 
Greenhorn
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The reason for C is tat when you using property based access, the accessor methods(getter/setter) should be public or protected. It cant b private or default.
 
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