Enumerations in Hibernate

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?

76727 次浏览

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>

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