Data Access Manager

Hi all

I had to design a data access layer framework (yes, I DID suggest Hibernate at the time, duffy ;-)) and came up with a rather good solution, IMHO. As the data access should be generated by a tool, there's but one possibility : map one DTO per table and populate them in the DAO. That's how it was before I arrived and it won't change.

Here is how it works :

publicinterface DAO{

// marker interface

}

// DAO interface for table 'xxx'

publicinterface XxxDAOextends DAO{

publicstaticfinalclass Row{

// column mappings to private java fields

// full constructor

// public getters & setters

}

public Row get(/* primary key */);

public Set<Row> select(/* index */);

publicint insert(Row row);// returns the serial if any

publicvoid update(/* primary key */, Row row);

publicvoid delete(Row row);

}

It is sufficient to explain my problem :

1. there's no primary key in our tables (eeeeeeeeewwwww, I know, nobody listens to me)

2. OTOH there may be multiple unique indices

3. ... and of course many multiple non unique indices

instead of creating getX(), getY(), ..., selectX(), selectY(), blablabla... methods with as many parameters as the respective index holds, I'd like to be able to do something like :

public Row get(Key key);// any existing unique index

public Set<Row> select(Index index);// any existing non unique index

publicint insert(Row row);// returns the serial if any

publicvoid update(Key key, Row row);// here 'key' would be the "main" unique index (I'll deal with that ;))

publicvoid delete(Row row);

But as soon as I start to think about how to modify the SQL implementation, I'm quite stuck. How could the (SQL)DAO know which key it receives and then build the query in an appropriate way ? I can't give any SQL responsibility to the Key class since it's intended to remain technology-independent, and a factory sounds heavy and dodgy to me...

Will I have to duplicate these get and select methods and give them unpronouncable names based on their index (indices can hold the same data types in the same order, unfortunately, that's why the Key/Index classes would have helped) ?

Do I have to design generic Key and Index classes that can be used as DTO for any query constraints (like an array containing the index fields as Objects)... by doing so, I stop enforcing that XxxDAO should only receive XxxKey and XxxIndex...

This problem is driving me mad, any help is welcome

[4030 byte] By [Torajiroua] at [2007-10-2 0:39:45]