OR mapping for java.util.Hashtables?

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Philipp Leitner - 12 Jul 2006 08:38 GMT

Hi all,

I was just recently wondering how you (or, for that matter, any
standard OR mapping library like Hibernate) would map a
java.util.Collection datastructure to a relational database? I guess
there has to be a well-known approach to that problem - I just can't
find it for the for the life of me :-)

Can anybody help me out on that? Precisely I need to map a
java.util.Hashtable to a HSQL database without using any specific OR
library.

thx in advance,
Philipp

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Oliver Wong - 12 Jul 2006 22:19 GMT

> Hi all,
>
[quoted text clipped - 3 lines]
> there has to be a well-known approach to that problem - I just can't
> find it for the for the life of me :-)

Different data structures would get mapped differently.

> Can anybody help me out on that? Precisely I need to map a
> java.util.Hashtable to a HSQL database without using any specific OR
> library.

Store the keys somehow. Assume the keys have an ID.
Store the values somehow. Assume the values have an ID.

If you only need to store one Hashtable, you can create an SQL table to
represent that table with two columns. The first column is a reference to a
key id, and the second column is a reference to a value id. I.e. you're
storing a relationship between a key and a value.

If you need to store multiple hashtables, add a third column which is
the ID of the hashtable to which the relationship belongs.

- Oliver

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Philipp Leitner - 13 Jul 2006 08:17 GMT

> Store the keys somehow. Assume the keys have an ID.
> Store the values somehow. Assume the values have an ID.
[quoted text clipped - 3 lines]
> key id, and the second column is a reference to a value id. I.e. you're
> storing a relationship between a key and a value.

arg ... I knew there had to be a simple way that I just didn't see. You
opened my eyes there - thanks a lot Oliver.

/philipp

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OR mapping for java.util.Hashtables?

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