Hibernate @Enumerated mapping

Question

Hibernate provides @Enumerated annotation which supports two types of Enum mapping either using ORDINAL or STRING. When w

Answer 1

public enum Status
{
    OPEN("O"),
    WAITLIST("W"),
    COMPLETE("C")

private String description;

private Status(String description)
{
   this.description = description;
}

public String getDescription()
{
    return description;
}
}

and then when you read it:

Status.OPEN.getDescription()

Answer 2

The best to customize mapping for enums is to use AttributeConverter i.e:

@Entity
public class Person {
    ...
    @Basic
    @Convert( converter=GenderConverter.class )
    public Gender gender;
}

public enum Gender {
    MALE( 'M' ),
    FEMALE( 'F' );

    private final char code;

    private Gender(char code) {
        this.code = code;
    }

    public char getCode() {
        return code;
    }

    public static Gender fromCode(char code) {
        if ( code == 'M' || code == 'm' ) {
            return MALE;
        }
        if ( code == 'F' || code == 'f' ) {
            return FEMALE;
        }
        throw ...
    }
}

@Converter
public class GenderConverter
        implements AttributeConverter<Gender, Character> {

    public Character convertToDatabaseColumn(Gender value) {
        if ( value == null ) {
            return null;
        }

        return value.getCode();
    }

    public Gender convertToEntityAttribute(Character value) {
        if ( value == null ) {
            return null;
        }

        return Gender.fromCode( value );
    }
}

You can find it in Hibernate docs: http://docs.jboss.org/hibernate/orm/5.0/mappingGuide/en-US/html_single/#d5e678

Answer 3

Check these two articles - http://community.jboss.org/wiki/Java5EnumUserType and http://community.jboss.org/wiki/UserTypeforpersistingaTypesafeEnumerationwithaVARCHARcolumn

They solve the problem by a custom UserType.

Answer 4

Here is an example which uses annotations.

http://www.gabiaxel.com/2011/01/better-enum-mapping-with-hibernate.html

It's still based off of a custom UserType. Four and a half years later and I'm still not aware of a better way to do this.

Typically, I persist my enum values as a char / int, some simple ID, then use a transient method that finds the appropriate enum by the simple ID value, e.g.

@Transient
public MyEnum getMyEnum() {
    return MyEnum.findById(simpleId); // 
}

and...

public enum MyEnum {
    FOO('F'),
    BAR('B');

    private char id;
    private static Map<Character, MyEnum> myEnumById = new HashMap<Character, MyEnum>();

    static {
        for (MyEnum myEnum : values()) {
            myEnumById.put(myEnum.getId(), myEnum);
        }
    }

    private MyEnum(char id) {
        this.id = id;
    }

    public static MyEnum findById(char id) {
        return myEnumById.get(id);
    }

    public char getId() {
        return id;
    }
}