Can you tell something about one to many associations and how can we u

1.	Can you tell something about one to many associations and how can we use them in Hibernate?
Answer» The one-to-many association is the most commonly used which indicates that one object is linked/associated with multiple objects. For example, one PERSON can own multiple cars. Hibernate One To Many Mapping In Hibernate, we can achieve this by using @OnetoMany of JPA ANNOTATIONS in the model classes. Consider the above example of a person having multiple cars as SHOWN below: @Entity@Table(name="Person")PUBLIC class Person { //... @OneToMany(mappedBy="owner") private Set<Car> cars; // getters and setters} In the Person class, we have defined the car's property to have @OneToMany association. The Car class would have owned property that is used by the mappedBy variable in the Person class. The Car class is as shown below: @Entity@Table(name="Car")public class Car { // Other Properties @ManyToOne @JoinColumn(name="person_id", nullable=false) private Person owner; public Car() {} // getters and setters} @ManyToOne annotation indicates that many INSTANCES of an entity are mapped to one instance of another entity – many cars of one person.

Can you tell something about one to many associations and how can we use them in Hibernate?

Answer»

The one-to-many association is the most commonly used which indicates that one object is linked/associated with multiple objects.

For example, one PERSON can own multiple cars.

Hibernate One To Many Mapping

In Hibernate, we can achieve this by using @OnetoMany of JPA ANNOTATIONS in the model classes. Consider the above example of a person having multiple cars as SHOWN below:

@Entity@Table(name="Person")PUBLIC class Person { //... @OneToMany(mappedBy="owner") private Set<Car> cars; // getters and setters}

In the Person class, we have defined the car's property to have @OneToMany association. The Car class would have owned property that is used by the mappedBy variable in the Person class. The Car class is as shown below:

@Entity@Table(name="Car")public class Car { // Other Properties @ManyToOne @JoinColumn(name="person_id", nullable=false) private Person owner; public Car() {} // getters and setters}

@ManyToOne annotation indicates that many INSTANCES of an entity are mapped to one instance of another entity – many cars of one person.

Can you tell something about one to many associations and how can we use them in Hibernate?

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