Map enum in JPA with fixed values ?
- by Kartoch
I'm looking for the different ways to map an enum using JPA. I especially want to set the integer value of each enum entry and to save only the integer value.
@Entity
@Table(name = "AUTHORITY_")
public class Authority implements Serializable {
public enum Right {
READ(100), WRITE(200), EDITOR (300);
private int value;
Right(int value) { this.value = value; }
public int getValue() { return value; }
};
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "AUTHORITY_ID")
private Long id;
// the enum to map :
private Right right;
}
A simple solution is to use the Enumerated annotation with EnumType.ORDINAL:
@Column(name = "RIGHT")
@Enumerated(EnumType.ORDINAL)
private Right right;
But in this case JPA maps the enum index (0,1,2) and not the value I want (100,200,300).
Th two solutions I found do not seem simple...
First Solution
A solution, proposed here, uses @PrePersist and @PostLoad to convert the enum to an other field and mark the enum field as transient:
@Basic
private int intValueForAnEnum;
@PrePersist
void populateDBFields() {
intValueForAnEnum = right.getValue();
}
@PostLoad
void populateTransientFields() {
right = Right.valueOf(intValueForAnEnum);
}
Second Solution
The second solution proposed here proposed a generic conversion object, but still seems heavy and hibernate-oriented (@Type doesn't seem to exist in JEE):
@Type(
type = "org.appfuse.tutorial.commons.hibernate.GenericEnumUserType",
parameters = {
@Parameter(
name = "enumClass",
value = "Authority$Right"),
@Parameter(
name = "identifierMethod",
value = "toInt"),
@Parameter(
name = "valueOfMethod",
value = "fromInt")
}
)
Is there any other solutions ?
I've several ideas in mind but I don't know if they exist in JPA:
use the setter and getter methods of right member of Authority Class when loading and saving the Authority object
an equivalent idea would be to tell JPA what are the methods of Right enum to convert enum to int and int to enum
Because I'm using Spring, is there any way to tell JPA to use a specific converter (RightEditor) ?
