Re: Talking to multiple database types with Cayenne.

From: Michael Shea (mik..itido.com)
Date: Tue Oct 21 2008 - 10:12:28 EDT

  • Next message: Robert Zeigler: "Re: Talking to multiple database types with Cayenne."

    Hi Andrus,

    Thanks for your reply... Of course, this is almost exactly what Cayenne
    is for. I erred in the question I was asking, unfortunately, so I will
    ask it properly this time... =). I really just have a minor question to ask:

    My two database schemas are *almost* identical, but not quite. The MySQL
    database creates primary keys on certain tables by using an
    AUTOINCREMENT column. The Oracle database creates primary keys on the
    equivalent tables by using a custom sequence. Is there any way for me to
    change the primary key generation strategy depending on which DBMS is in
    use? Or will I have to choose a strategy that works equally on both
    Oracle and on MySQL (ie, switch to using the default strategy?).

    I would ideally like to continue using the auto-increment columns on
    MySQL, since that intuitively seems like the most efficient method to
    me. I have experimented with customizing the mapping.xml file at runtime
    based on which type of database I'll be using, before making any calls
    to cayenne, that seems to work. But it's also pretty hacky, and will
    make maintenance more painful.

    Thanks,

    Mike Shea.

    > Hi Michael,
    >
    > Cayenne will detect the database type automatically on startup and use
    > the right adapter. So yes, use JNDI to abstract connection
    > information, beyond that no need for any extra tricks. You generic
    > Cayenne mapping will just work regardless of the db type.
    >
    > Andrus
    >
    >
    >
    > On Oct 20, 2008, at 11:42 AM, Michael Shea wrote:
    >
    >> Hi guys,
    >>
    >> I am working on a project in which I have to support multiple
    >> database types. They do not have to be supported simultaneously - I
    >> need my program to be able to run whether I am using an Oracle
    >> database or a MySQL database (the databases will have the same
    >> schema), but the database type does not change at runtime.
    >>
    >> I am wondering if there are any best practices or recommendations for
    >> how to approach this problem. Currently, I am planning on simply
    >> creating two sets of cayenne configuration files in different
    >> directories (ie, a map.xml and a cayenne.xml file), and just adding
    >> one or the other of these directories to the classpath, depending on
    >> some initial configuration parameters that tell me what type of
    >> database I'm accessing. The datasource is defined via JNDI.
    >>
    >> Does anyone think that this is a good idea or a bad idea, or have a
    >> better way of doing this? =) I am using Cayenne 2.0.4.
    >>
    >> Thanks!
    >>
    >>
    >> Mike Shea.
    >>
    >

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