[Java] [JPA] @mapkey example

ER Diagram.png

Shop.java

import javax.persistence.*;
import java.util.Map;

@Entity
public class Shop {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    public int id;
    public String name;

    @ElementCollection  // (Required) if the map value is a basic type.
    @CollectionTable(name = "REVENUE",
            joinColumns = @JoinColumn(name = "STORE"))
    @Column(name = "MONEY")
    @MapKeyTemporal(TemporalType.DATE)
    public Map<java.util.Date, Integer> income;

    ...
}

key\value	@CollectionTable	uni-directional @OneToMany	bi-directional @OneToMany	@ManyToMany
@MapKeyColumn	link	link	link	link
@MapKeyTemporal	link	link	link	link
@MapKeyEnumerated	link	link	link	link
@MapKeyJoinColumn	link	link	link	link

• @MapKeyColumn if the map key is a basic type.
  If you don't specify the column name, the name of the property is «field»_KEY
• @MapKeyEnumerated/[@MapKeyTemporal](https://docs.oracle.com/javaee/7/api/javax/persistence/MapKeyTemporal.html @MapKeyTemporal) if the map key type is respectively an enum or a Date.
• @MapKeyJoinColumn/@MapKeyJoinColumns if the map key type is another entity.

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• If the map key is NON-basic entity, the map key MUST be persisted (saved) before persist the holder.
• If the relationship is many-to-many and the map value is NON-basic entity, the map value also MUST be persisted before persist the holder.

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• @ElementCollection is required if the map value is a basic type.
  Corresponding config annotation are @CollectionTable and @Column.
• if the map value is NON-basic type, it's required either @OneToMany or @ManyToMany.
  Corresponding config annotation is @JoinTable.