Mapping enum to a table with hibernate annotation

Question

I have a table DEAL and a table DEAL_TYPE. I would like to map this code:

public class Deal {    DealType type; }  public enum DealType {    BASE("Base"), EXTRA("Extra"); } 

The problem is that the data already exist in the database. And I'm having a hard time mapping the classes to the database.

The database looks something like that:

   TABLE DEAL {       Long id;       Long typeId;    }     TABLE DEAL_TYPE {        Long id;        String text;    } 

I know I could use a simple @OneToMany relationship from deal to deal type, but I would prefer to use an enum. Is this possible?

I almost got it working by using a EnumType.ORDINAL type. But unfortunately, my IDs in my deal type table are not sequential, and do not start at 1.

Any suggestions?

Answer 1

Hibernate is kind of terrible at Enums. It's a strange failing of an otherwise pretty good ORM. The "easiest" way to get around it is to declare your Enum a custom hibernate type. Fortunately, Hibernate wrote an example implementation which you can crib verbatim into your app:

http://www.hibernate.org/265.html

They even include instructions on how to use it. This is the pattern I use whenever I end up with the need to persist enums.

Answer 2

I've created a similar class like the one suggested by hibernate only that is configurable and there is no need to create a new type only for this persistence.

Can be used like

@Type(type = "ro.raisercostin.hibernate.EnumUserType", parameters = @Parameter(name = "type", value = "DealType")) DealType dealType; 

I added an implementation of ParameterizedType to support the passed parameter.

public class EnumUserType implements UserType, ParameterizedType {      private static final int[] SQL_TYPES = { Types.VARCHAR };     private Class clazz = null;      public EnumUserType() {     }      @Override     public void setParameterValues(Properties parameters) {         String className = (String) parameters.get("type");         try {             this.clazz = Class.forName(className);         } catch (ClassNotFoundException e) {             throw new RuntimeException("Couldn't get the class for name [" + className + "].", e);         }     }      public int[] sqlTypes() {         return SQL_TYPES;     }      public Class returnedClass() {         return clazz;     }      public Object nullSafeGet(ResultSet resultSet, String[] names, Object owner) throws HibernateException,             SQLException {         String name = resultSet.getString(names[0]);         Object result = null;         if (!resultSet.wasNull()) {             result = Enum.valueOf(clazz, name);         }         return result;     }      public void nullSafeSet(PreparedStatement preparedStatement, Object value, int index) throws HibernateException,             SQLException {         if (null == value) {             preparedStatement.setNull(index, Types.VARCHAR);         } else {             preparedStatement.setString(index, ((Enum) value).name());         }     }      public Object deepCopy(Object value) throws HibernateException {         return value;     }      public boolean isMutable() {         return false;     }      public Object assemble(Serializable cached, Object owner) throws HibernateException {         return cached;     }      public Serializable disassemble(Object value) throws HibernateException {         return (Serializable) value;     }      public Object replace(Object original, Object target, Object owner) throws HibernateException {         return original;     }      public int hashCode(Object x) throws HibernateException {         return x.hashCode();     }      public boolean equals(Object x, Object y) throws HibernateException {         if (x == y) {             return true;         }         if ((null == x) || (null == y)) {             return false;         }         return x.equals(y);     } }