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?
Solution
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
OTHER TIPS
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>