Given the code fragments: Which action completes this composite primary key implementation?

Question

Exhibit

Options

• AAdd @IdClass annotation at line 1.
• BAdd @Embeddable annotation at line 1 and replace both @Id annotations with @EmbeddedId
• CAdd @IdClass(ContactId.class) annotation at line 2.
• DAdd @Embeddable annotation at line 1 and @EmbeddedId(ContactId.class) at line 2.

• A
  12% (2)
• B
  6% (1)
• D
  82% (14)

Explanation

Option D correctly implements the @EmbeddedId composite key strategy: @Embeddable must annotate the ContactId class (marking it as an embeddable value type that JPA can map), while @EmbeddedId on the entity's ContactId field tells JPA that this single embedded object represents the full composite key. Together, these two annotations form a complete and valid implementation.

Why the distractors fail:

• A is wrong because @IdClass belongs on the entity class (line 2), not the ID class (line 1), and even then it requires @Id on each individual key field in the entity.
• B is wrong because @EmbeddedId replaces the single ContactId field in the entity - you don't annotate multiple @Id fields; those belong to the @IdClass strategy, not @EmbeddedId.
• C is wrong because @IdClass(ContactId.class) alone is insufficient - the entity still needs @Id on each individual key field, and the ContactId class must have matching fields (no @Embeddable needed for this approach, but more annotations are required).

Memory tip: Think EMBEDdable → EMBEDdedId - if the key class is @Embeddable, the entity field must be @EmbeddedId. If you see @IdClass, look for individual @Id annotations on the entity fields instead.

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