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List:       ojb-user
Subject:    Persisting a HashMap of objects with composite primary keys
From:       Laran Evans <lc278 () cornell ! edu>
Date:       2005-12-01 18:24:18
Message-ID: 30ec9fe20512011024i29fae022ybdb78e349f0fc679 () mail ! gmail ! com
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How would I persist class A below?

C and D have a composite primary key in the database.
The primary key for C is innermostOneKey and referenceToOutermostKey.
The primary key for D is innermostOneKey and referenceToOutermostKey.

My understanding is that with ManageableHashMap, when loading from the
database the key in the Map is set to the primary key. Clearly that
won't work with a composite key.

I'd really rather not use a reference table however if at all
possible. The other alternative is to use ManageableArrayLists instead
of Maps. This has other side-effects however which lead to a slightly
unclean API. I'd like to avoid that if possible, but will resort to it
if it is the simplest solution.

Is there any way to do this?

---

class A {
 Map outermost;
}

class B {
 Integer outermostKey;
 Map innermostOne;
 Map innermostTwo;
}

class C {
 Integer innermostOneKey;
 Integer outermostKey;
 ...
}

class D {
 Integer innermostTwoKey;
 Integer outermostKey;
 ...
}

class Main {
 public static void main(String[] args) {
  A a = new A();
  B b = new B();
  C c = new C();
  D d = new D();

  c.outerMostKey = b.outermostKey;
  d.outerMostKey = b.outermostKey;

  b.innermostOne.put(c.innermostOneKey, c);
  b.innermostTwo.put(d.innermostTwoKey, d);

  a.outermost.put(b.outermostKey, b);
  ...
 }
}

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