Question

@Entity
public class Husband implements Serializable {

   @Id
   private int id;

   private String name;

   @OneToOne
   private Wife wife;

}

@Entity
public class Wife implements Serializable {

   @Id
   private int id;

   private String name;

   @OneToOne(mappedBy="wife")
   private Husband husband;

}

1. What is Serializable in broad term?
2. Why does a class implements Serializable interface?
3. Why does the husband member alone have @OnetoOne(mappedBy =”Wife”), but the wife member does not have @OnetoOne(mappedBy=”husband”)

Answer 1

1. Serialization, in broad terms, is the way Java provides developers to persist the state of any object to a persistent store.

2. If a developer wants that for some reason instance of his coded class should be persisted to a backing store, then the class needs to be declared as implementing Serializable.

3. The above code represents a One to One relationship between a Husband and a Wife. Which basically means that each wife is related to one husband and each husband is related to one wife. 🙂 Also in the above relationship, the Husband is the master of the relationship [in Entity-Relationship terms] and that is why Wife says that it is mapped/associated to Husband by the Husband and not the other way around. Which means Husband identifies its wife and not the other way around.