Re: Enums

From:

Wojtek <nowhere@a.com>

Newsgroups:

comp.lang.java.programmer

Date:

Mon, 24 Aug 2009 12:36:43 -0700

Message-ID:

<mn.c2f47d981dc7ab3e.70216@a.com>

Lew wrote :

Alessio Stalla wrote :

You can persist the name of the constant, and retrieve the Enum
instance with Enum.valueOf(MyEnum.class, name). Or, depending on the
context, you can persist the serialized Enum (enums are serializable
by default).

Wojtek <nowh...@a.com> wrote:

Ok.

But, silly me, I sometimes rename Enum values. Yes, yes, poor design
and all, but it happens.

And that doesn't risk changing the ordinal? Or if there were a way to
set the ordinal (as there is, as long as by "ordinal" you mean a
custom value retrieved by a method 'getOrdinal()') what's to prevent
you from changing that?

// do not change as it is persisted!
private static final int MY_ENUM_ID = 1;

public enum IsEnum
{
   MY_ENUM(MY_ENUM_ID);

   private int id;

   private IsEnum( int databaseID )
   {
     id = databaseID;
   }

   public int getDatabaseID()
   {
      return id;
   }
}

and then, of course, some code to scan the enums and find the id you
are looking for.

This is safe against the Java compiler setting ordinals and renaming
enums.

--
Wojtek :-)