Java – JPA inheritance is not dry

I have inherited the job, but it's not very dry I have to repeat the coding for each new bolt type It's best to show my course and explain it further

Parent of my boltspec (dimensions related to fasteners)

@Entity
@Table(name="BoltSpecs")
@IdClass(BoltSpecCK.class)
@DiscriminatorColumn(name="boltType" )
public abstract class BoltSpec implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    private String size;

    @Id
    @Enumerated(EnumType.STRING)
    private EnumBoltType boltType;

    private BigDecimal basic_major_diameter = BigDecimal.ZERO;

And my enumbolttype

public enum EnumBoltType {
    CYLINDER_HEAD_CAP_SCREW("CYLINDER HEAD CAP SCREW",EnumHeadType.CYL),HEX_CAP_SCREW("HEX CAP SCREW",EnumHeadType.HEX),HEAVY_HEX_CAP_SCREW("HEAVY HEX CAP SCREW",HEX_BOLT("HEX BOLT",HEAVY_HEX_BOLT("HEAVY HEX BOLT",FLAT_COUNTERSUNK_HEAD_CAP_SCREW("FLAT COUNTERSUNK HEAD CAP SCREW",EnumHeadType.CONE);

Then I must have duplicate classes, i.e. hexcapscrew, heavyhexcapscrew, etc. and hexcapscrew spec, heavyhexcapscrew spec, etc., even if they have similar boltscpec attributes (not numeric values)

public class HexCapScrew extends Bolt {
    private static final long serialVersionUID = 1L;
    private static HexCapScrewSpec spec;
    public HexCapScrew() {
        super(spec);
    }
}

public class HeavyHexCapScrew extends Bolt {
    private static final long serialVersionUID = 1L;
    private static HeavyHexCapScrewSpec spec;
    public HeavyHexCapScrew () {
        super(spec);
    }
}

…

@Entity
@DiscriminatorValue("HEX_CAP_SCREW")
public class HexCapScrewSpec extends BoltSpec implements Serializable {
    private static final long serialVersionUID = 1L;

    public HexCapScrewSpec() {
        super();
    }

    private BigDecimal flat_diameter = BigDecimal.ZERO;
    ...

@Entity
@DiscriminatorValue("HEAVY_HEX_CAP_SCREW")
public class HeavyHexCapScrewSpec extends BoltSpec implements Serializable {
    private static final long serialVersionUID = 1L;

    public HeavyHexCapScrewSpec() {
        super();
    }

    private BigDecimal flat_diameter = BigDecimal.ZERO;
    ...

This specification is different

@Entity
@DiscriminatorValue("FLAT_COUNTERSUNK_HEAD_CAP_SCREW")
public class FlatHeadCapScrewSpec extends BoltSpec implements Serializable {
    private static final long serialVersionUID = 1L;

    public FlatHeadCapScrewSpec() {
        super();
    }

    private BigDecimal cone_angle = BigDecimal.ZERO;
    ...

Here are some examples of import SQL data

insert into BoltSpecs (basic_size,basic_major_diameter,boltType,flat_diameter) 
    values ('2-3/4','2.75','HEX_CAP_SCREW','3.988')
    values ('3','3','4.35')
    values ('3/8','0.375','HEAVY_HEX_CAP_SCREW','0.669')

insert into BoltSpecs (basic_size,cone_angle) 
    values ('2-3/4','FLAT_COUNTERSUNK_HEAD_CAP_SCREW','39.77')

I have a drop-down menu at the front end. The user selects the bolt type and needs to use the applicable bolt specification I don't want to modify my import Check and place the bolt head type I risk calling hee hex bolt Is there any way to do multiple discriminatorvalues? Like:

@Entity
@DiscriminatorValue("HEX_CAP_SCREW,HEAVY_HEX_CAP_SCREW,HEX_BOLT,HEAVY_HEX_BOLT")
public class BoltSpecHexHead extends BoltSpec implements Serializable {
    private static final long serialVersionUID = 1L;

    public BoltSpecHexHead () {
        super();
    }

    private BigDecimal flat_diameter = BigDecimal.ZERO;

…

public class BoltHexHead extends Bolt {
    private static final long serialVersionUID = 1L;
    private static BoltSpecHexHead spec;
    public BoltSpecHexHead () {
        super(spec);
    }
}

Or how can I Ping enumheadtype as the authentication value? Bolts with similar heads (enumheadtype.cyl, hex and cone) have similar specifications

Solution

I can implement the solution using @ discriminatorformula

@Entity
@Table(name="BoltSpecs")
@IdClass(BoltSpecCK.class)
//@DiscriminatorColumn(name="boltType" )
@DiscriminatorFormula("case when boltType in ('CYLINDER_HEAD_CAP_SCREW') then 'HEX' 
   when boltType in ('HEX_CAP_SCREW','HEX_BOLT','HEAVY_HEX_BOLT') then 'HEX' 
   when boltType in ('FLAT_COUNTERSUNK_HEAD_CAP_SCREW') then 'CONE' end")

public abstract class BoltSpec implements Serializable {