I am going through some code and it uses nested @JoinColumn for one of the associations, as following:
@ManyToOne(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
@JoinColumns({@JoinColumn(name = "QuestId"), @JoinColumn(name = "GuildId")})
private GuildQuests guildQuest;
I understand that when I do something like the following:
@ManyToOne(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
@JoinColumns(name="GuildQuestId")
private GuildQuests guildQuest;
I am creating a column with the name GuildQuestId in the table and it has a foreign key constraint with the entity GuildQuests.
However, what will the nested @JoinColumn(first code snippet) do?
Your first snippet is saying that you specify multiple foreign keys for the same association.
Example:
@ManyToOne
@JoinColumns({
@JoinColumn(name="ADDR_ID", referencedColumnName="ID"),
@JoinColumn(name="ADDR_ZIP", referencedColumnName="ZIP")
})
public Address getAddress() { return address; }
Edit: You're actually not creating any foreign keys with (both example) in the database. If you use for example Hibernate, Hibernate does not create any foreign keys on database level itself.