How to Specify Join Column Name for JPA @ElementCollection List

How can I specify the join column name for a JPA @ElementCollection list?

@ElementCollection
@JoinColumn(name = "custom_join_column")
private List<String> elements;

In Java Persistence API (JPA), when using the @ElementCollection annotation to define a collection of basic types or embeddable classes, specifying the join column name is crucial for proper mapping of the collection to a database table. This can be achieved using the @JoinColumn annotation alongside the @ElementCollection annotation.

@Entity
public class Parent {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @ElementCollection
    @CollectionTable(name = "parent_elements") // Specify the table name
    @JoinColumn(name = "parent_id") // Specify the join column name
    private List<String> elements;
}

Causes

• Incorrect mapping lead to default column names being used.
• Lack of clarity on how to map collections properly in JPA.
• Understanding complex relationships in entity classes.

Solutions

• Use @JoinColumn to explicitly specify the name of the join column used in the database.
• Make sure to define the collection with a correct mapping annotation like @ElementCollection.

Mistake: Not defining the @JoinColumn annotation.

Solution: Always use @JoinColumn to specify your desired join column name.

Mistake: Using the default table and column names without understanding their implications.

Solution: Clearly define your table and join column names to avoid unexpected behaviors.