I've got a database table with many columns (30+) and if I mapped only one class to it i'd be retrieving too much data on each db call.

Are there any foreseeable problems with mapping 2 different persistent classes to the same database table?

Any other ways of overcoming this? Can you lazy load certain properties or components?

Of course you can,

Two solutions:
1- Define a super class for two entities, and use table per class hierarchy strategy.
2- Define two classes, each with a discriminator value with attribute force="true"

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don't forget credits.

Unfortunately, I can't alter the table structure because I'm working with a content management system that is quite restrictive.

you may declare properties as lazy or proxy so they do not load when you call session.get(). If you are using hibernate3 when you call to session.load() no property is loaded from database unless you call a getter from a property different than id.

are there any other solutions that do not involve byte code instrumentation?

entity-name, look for it in the docs.

there must be a way you distinguish between two entities, isn't it?

so use it as a discriminator column, or discriminator formula!

But entity-name is for one class to multiple tables right? I'm doing the opposite, multiple classes one table.

For example,
[code]
<class name="ClassOne" table="Information" >
<-- map columns 1-5 -->
</class>

<class name="ClassTwo" table="Information" >
<-- map columns 6-10 -->
</class>
[/code]

I'm just worried that this might cause some weird side effects. One thing i should mention is that the classes are immutable so i don't have to worry about inserts or updates.

As for discriminators, this is not exactly an inheritance model. Its more delegation like a one-to-one mapping or a class with components.

so multiple class'es to one table is not a problem *unless* the instances map to the same rows ...then you have to be carefull.

If they are completely disjunct no the only issue is if you are using versioning since they will "argue' against which entity should win the "edit right".

Are you sure you don't want to have component's here instead ?

So you're saying if i'm not doing any insertions or updates it should be fine right? Basically I am working with a Content management system so all i do is read and query.

I was thinking about using components but it requires byte code modification if i want to lazy load the components. I always thought that one of the strengths of hibernate is that it didn't require byte code modification so I'm not sure if i want to go down that path.

One more thing. Is it possible to retrieve the component itself without retrieving the main class that holds the component?

if it is pure read then I don't see any major problems with this approach.


and regarding getting the component then you should be able to do:

select p.compo from Parent

to just get the compo returned.