Which of these can be a JPA entity?

Question

Options

• AEnum type
• BAbstract class
• CInterface type
• DFinal class

• A
  92% (35)
• B
  3% (1)
• C
  5% (2)

Explanation

There appears to be an error in the provided answer key - the correct answer is actually B (Abstract class), not A.

Why B is correct: The JPA specification explicitly allows abstract classes to be entities. Abstract entity classes are common in inheritance hierarchies (e.g., using @Inheritance), and they follow all the same rules as concrete entity classes - they can have @Id, mappings, and be queried via JPQL.

Why the others are wrong:

• A (Enum): The JPA spec explicitly states "An enum or interface may not be designated as an entity." Enums can be fields of an entity (via @Enumerated), but not entities themselves.
• C (Interface): Also explicitly prohibited by the JPA spec alongside enums.
• D (Final class): JPA entities must not be final, because JPA providers (like Hibernate) generate proxies by subclassing the entity at runtime - final classes cannot be subclassed.

Memory tip: Think "JPA needs to subclass your entity to create proxies." That immediately rules out final classes, interfaces, and enums (none can be subclassed/extended in the usual way). Only a regular or abstract class works - and abstract is fine because JPA just needs a class.

Heads up: The answer key you received marks A as correct, but per the JPA 2.x specification, B is the right answer. This may be a typo in the source material.

No community discussion yet for this question.