Embeddable and Embedded in JPA

@Embeddable and @Embedded are used to model value objects in JPA. They allow you to group related fields together without creating a separate table.

This is a clean way to represent conceptual objects like Address, AuditInfo, or Money inside an entity.

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What is @Embeddable?

An embeddable is a class whose fields are:

• Stored as columns in the owning entity’s table
• Do NOT have their own table
• Do NOT have their own identity (no primary key)

It represents a value, not an entity.

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What is @Embedded?

@Embedded is used in an entity to:

• Include an embeddable object
• Flatten its fields into the entity table

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Why Embeddables Are Needed

Without embeddables:

• Entities become large and cluttered
• Repeated fields appear in multiple entities
• Poor readability and duplication

Embeddables help:

• Group related fields logically
• Improve readability
• Reuse common structures
• Follow SRP (Single Responsibility Principle)

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Simple Example: Address (Very Common)

Embeddable Class

@Embeddable
public class Address {

    private String street;
    private String city;
    private String state;
    private String pincode;
}

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Entity Using Embedded

@Entity
public class Customer {

    @Id
    private Long id;

    private String name;

    @Embedded
    private Address address;
}

Database Table Structure

customer
--------
id
name
street
city
state
pincode

• 👉 No separate address table
• 👉 Address fields are flattened into customer table

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Important Characteristics

Embeddables:

• ❌ Cannot be queried independently
• ❌ Cannot be shared as entities
• ❌ Do not have lifecycle

Embeddables:

• ✔ Are part of the owning entity
• ✔ Are persisted automatically
• ✔ Follow the entity’s lifecycle

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Using Multiple Embedded Objects

@Entity
public class Branch {

    @Embedded
    private Address officeAddress;

    @Embedded
    @AttributeOverrides({
        @AttributeOverride(name = "street", column = @Column(name = "billing_street")),
        @AttributeOverride(name = "city", column = @Column(name = "billing_city")),
        @AttributeOverride(name = "state", column = @Column(name = "billing_state")),
        @AttributeOverride(name = "pincode", column = @Column(name = "billing_pincode"))
    })
    private Address billingAddress;
}

Use AttributeOverrides

When:

• Same embeddable is used multiple times
• Column names clash

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Embeddable vs Entity

Aspect	Embeddable	Entity
Identity	❌ No ID	✔ Has ID
Table	❌ No table	✔ Own table
Lifecycle	❌ No	✔ Yes
Queryable	❌ No	✔ Yes
Use case	Value object	Business object

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When NOT to Use Embeddable

Do NOT use embeddable if:

• Object has its own lifecycle
• Object needs separate table
• Object is shared across many entities
• Object needs independent queries

In such cases → use an entity.

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Summary

• Embeddables are value objects
• Stored in the same table as entity
• No identity, no lifecycle
• Use @AttributeOverrides for column conflicts
• Good for grouping related fields