Java.Hibernate.Middle.How do you map an embeddable object in Hibernate?

✅ Short Answer

In Hibernate/JPA, you map an embeddable object using @Embeddable on the value class, and @Embedded on the owning entity’s field → the embeddable’s fields become columns in the entity’s table.

🔎 Detailed Explanation

🔹 Embeddables are reusable value objects:

• They don’t have their own table → they’re embedded into the owning entity’s table.
• Great for grouping related fields (e.g., address, monetary amount, coordinates) into a clean object.
• Avoids cluttering entity classes with dozens of flat fields.

🔹 Steps to map an embeddable

✅ 1) Create the embeddable class

@Embeddable
public class Address {
    private String street;
    private String city;
    private String zipCode;
}

✅ 2) Add the embeddable to an entity

@Entity
public class User {
    @Id
    private Long id;

    private String name;

    @Embedded
    private Address address; // fields of Address become columns in User table
}

🔹 What happens in the database?

• Hibernate maps User into a single table with columns:
  • id, name, street, city, zip_code.

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🔹 Customizing column names with @AttributeOverrides
If you embed the same embeddable twice or want custom column names, use @AttributeOverrides:

@Embedded
@AttributeOverrides({
    @AttributeOverride(name = "street", column = @Column(name = "home_street")),
    @AttributeOverride(name = "city", column = @Column(name = "home_city")),
    @AttributeOverride(name = "zipCode", column = @Column(name = "home_zip"))
})
private Address homeAddress;

@Embedded
@AttributeOverrides({
    @AttributeOverride(name = "street", column = @Column(name = "work_street")),
    @AttributeOverride(name = "city", column = @Column(name = "work_city")),
    @AttributeOverride(name = "zipCode", column = @Column(name = "work_zip"))
})
private Address workAddress;

✅ This allows you to embed the same class multiple times in an entity.

📊 Benefits of Embeddables

✅ Improves code reuse and domain model clarity → avoids repetition.
✅ Keeps the database normalized without creating extra tables.
✅ Supports nested embedding → embeddables can themselves embed other embeddables.

📌 Key Takeaways

✅ Annotate reusable value objects with @Embeddable, and use @Embedded in entities.
✅ Embeddables have no separate table → their fields become columns of the owning entity.
✅ Use @AttributeOverrides to control or disambiguate column names.