Better way to implement reverse mapping of custom enum ordinals?

[Tom Anderson]

'getEnum()' should be static.

Whoops, you're quite right, it should.

tom

 

[Lew]

Whoops, you're quite right, it should.

Aside: there is at least one approach to Hibernate serialization of enums
where the programmer provides for reflective use the names of the instance
method to convert an enum to an external value, and the static method for the
other direction. (IIRC they default to 'toString()' and 'valueOf()'.)

 

[Daniel Pitts]

But it's a type-safe int!

Actually, the way I see it is the public integer is an *external* key.
It is not controlled by the program, and therefor must be declared as a
magic number somewhere. The fact that it is being converted to and from
type-safe enums is at least a partial win. The best practices for
this situation would be to maintain the enum value for as much of the
time as possible.

For better control over this "best practice", it might make more sense
to make that a package protected value, and force the data-access code
to do the conversions immediately after read, and prior to write.

 

[Arne Vajhøj]

david.karr wrote:
Quite often databases will have columns that are stored as integers,
but represent enumerated values. In object-relational mapping, it's a
good idea to translate that integer value to the enumerated value it
represents.
[ SNIP ]

It's an even better idea to store the enumeration "name" as a varchar.

Agreed - and hold the integer:name mapping as a separate table.

Or don't even bother with integers in the database at all, but just use
the VARCHAR value.

Depending on the database using int referring with a table mapping
to varchar may provide better possibilities for constraints
in the database.

Arne