EnumAttributeConverter.java

@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<Character,Gender> {

	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 );
	}
}