Enumerations in Hibernate

Question

It is often useful to have a field in a DAO whose value comes from a Java enumeration. A typical example is a login DAO where you usually have a field that characterises the user as "NORMAL" or "ADMIN". In Hibernate, I would use the following 2 objects to represent this relationship in a (semi-)typesafe way:

class User {
    String username;
    String passwd;
    UserType type;
}

class UserType {
    private enum Type {ADMIN, NORMAL};
    private String type;

    //Setters/Getters for Hibernate
    public void setType(String type);
    public String getType();

    //Setters/Getters for user
    public void setUserType(UserType.Type t);
    public UserType.Type getUserType();

    public static UserType fromType(UserType.Type t);
}

This works, but I find the UserType class ungly and requiring too much bureaucracy just to store a couple of values. Ideally, Hibernate should support enum fields directly and would create an extra table to store the enumeration values.

My question is: Is there any way to directly map an enumeration class in Hibernate? If not, is my pattern for representing enumerations good enough or am I missing something? What other patterns do people use?

Answer 1

using hibernate or JPA annotations:

class User {
   @Enumerated(EnumType.STRING)
   UserType type
}

UserType is just a standard java 5 enum.

I can't imagine this is just limited to just annotations but I don't actually know how to do this with hbm files. It may be very version dependant, I'm guessing but I'm pretty sure that hibernate 3.2+ is required.

edit: it is possible in a hbm, but is a little messy, have a look at this forum thread

Answer 2

From the Hibernate documentation: http://www.hibernate.org/272.html

You can create a new typedef for each of your enums and reference the typedefs in the property tag.

Example Mapping - inline <type> tag

  <property name='suit'>
    <type name="EnumUserType">
      <param name="enumClassName">com.company.project.Suit</param>
    </type>
  </property>

Example Mapping - using <typedef>

  <typedef name="suit" class='EnumUserType'>
      <param name="enumClassName">com.company.project.Suit</param>
  </typedef>

  <class ...>
    <property name='suit' type='suit'/>
  </class>