There are two tables: Airplane and Engine

Engine: [Engine_ID, Engine_Name, Engine_Position, Airplane_Owner_ID].
Airplane: [Airplane_ID, Airplane_Name,...]
Engine_Position = {Right, Left}

Each plane has two engine (Left_Engine and Right_Engine). And a unique constraint on Engine (Airplane_Owner_ID, Engine_Position).
Therefore there are two one-to-one relationships defined between the Airplane and Engine tables.

How can these relationships be specified in Hibernate and related class in JPA?

The best way to do it is to change the schema as follows:

Engine: [Engine_ID, Engine_Name].
Airplane: [Airplane_ID, Airplane_Name, Left_Engine_ID, Right_Engine_ID]

This is a much better approach since you said that an engine can only have 2 engines. Using your previous schema, an airplane could end-up with 100 left engines and 300 right ones.

Would you please tell me the jpa?

Sure. Here's the best way to map a @OneToOne relationship with JPA and Hibernate.