I often like to set a mapped Entity Model property as an Enumerator type. The new Links feature we're building in NixMash Spring (more on that as it happens) uses a PostDisplayType enumerator.
We'll assign it on the Post entity displayType field like so.
Now we can save it to our database table VARCHAR(20) field as a String yet enjoy coding with its Enumerator properties in Java.
But instead of saving Strings to the database, the PostDisplayType ORDINAL value is being saved!
The Javax.Persistence @Access annotation is used to specify an access type to be applied to an entity class for mapping purposes. (Getting deeper into @Access, it can also be applied to fields, but that's “outside the scope of this post” as they say.) Its values are FIELD and PROPERTY. If not explicitly noted it defaults to whichever type of element assigned to the @Id value.
Our Model Class Signature:
See the problem? Our @Access type is PROPERTY (getDisplayType(), or on the getter methods.) But as we saw earlier, our @Enumerated annotation is on a FIELD.
We're in trouble here with more than just our @Enumerated annotation, but let's hypothetically say that the @Column is defined properly with our getter and we add @Enumerated to the field just for kicks. The result is that Hiberate ignores our @Enumerated settings and ordinals end up in our database.
The moral of the story is to define the mapped @Enumerated element with the correct FIELD/PROPERTY @Access setting for the class, and if not explicitly set, on the same element type as your @Id field.