Hibernate Composite Key Join

Question

I'm trying to use Spring Data to perform joined queries but one of my tables has a Composite Key and I'm not sure how to map the entities.

Here is an analogy of the data model:

table: device
pk=model_id
pk=serial_id
...

table: device_settings
pk=device_settings_id
fk=model_id
fk=serial_id
...

Here is an analogy of the code, which doesn't compile due to a "mappedby" attribute that is isn't present.

@Entity
@Table(name = "device_settings")
public class DeviceSettings {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "device_settings_id")
    private Long id;

    // Pretty sure this is the problem
    @OneToMany(targetEntity = Device.class, mappedBy = "deviceKey", cascade = {CascadeType.MERGE}, fetch = FetchType.EAGER)
    @JoinColumns({
        @JoinColumn(name = "model_id", referencedColumnName = "model_id"),
        @JoinColumn(name = "serial_id", referencedColumnName = "serial_id")})
    private List<Device> devices;
}

@Entity
@Table(name = "device")
public class Device {
    @Id
        private DeviceKey deviceKey;
    }
    ...
}


@Embeddable
public class DeviceKey implements Serializable {
    private static final long serialVersionUID = -1943684511893963184L;

    @Column(name = "model_id")
    private Long modelId;

    @Column(name = "serial_id")
    private Short serialId;
}

Answer 1

Associations marked as mappedBy must not define database mappings like @JoinTable or @JoinColumn

To achieve your scenario you have to define @ManyToOne:

@ManyToOne(cascade = {CascadeType.MERGE}, fetch = FetchType.EAGER)
    @JoinColumns({
        @JoinColumn(name = "model_id", referencedColumnName = "model_id"),
        @JoinColumn(name = "serial_id", referencedColumnName = "serial_id")})
     private Device device;

This will end up model_id, serial_id, device_settings_id

or

Define @JoinColumn in Device Entity Entities:

DeviceSettings :

    @Entity
    @Table(name = "device_settings")
    public class DeviceSettings {

        @Id
        @GeneratedValue(strategy = GenerationType.AUTO)
        @Column(name = "device_settings_id")
        private Long id;


        @OneToMany( mappedBy = "deviceSettings", cascade = {CascadeType.MERGE}, fetch = FetchType.EAGER)
         private List<Device> devices;
}

Device Entity :

@Entity
@Table(name = "device")
public class Device {

        @EmbeddedId
        private DeviceKey deviceKey;

        @ManyToOne
        @JoinColumn(name="device_settings_id")
        private DeviceSettings deviceSettings;
       //getters and setters
}

Note : you can decide which is the owner of the relationship and put your mappings accorindly either One Device has many device settings or other way around.