On 11/16/06, Henry Chen <[EMAIL PROTECTED]> wrote:
Thank you. Did you come up with any solution without Tapernate?
This is relatively simple if you aren't using a framework that explicitly prevents it. I use swing + hibernate to provide all the layers to my app underneath the web layer and it is trivial to provide access to multiple databases. I can define multiple data sources in my application context and then provide dao beans which use the appropriate data sources as well as service objects which utilize those daos. My web layer isn't even aware of the location of data. It just calls a method in the service layer, which may use DAOs from multiple databases to accomplish the necessary work. And with spring's nice declarative transactions, it is easy, within the confines of a JTA transaction in a J2EE container, to have a single transaction span db access to multiple databases, which is really convenient. In my app, I have a situation where my entire domain model is provided via hibernate to a single domain db, but the huge volume of data that I need to provide access to for reporting is in 2 separate data warehouses. The domain entities are all accessed via DAO's using spring's built in hibernate dao support classes, and I use pure JDBC to access the 2 separate data warehouses. So I have about 25 DAOs using the hibernate data source (one for each entity), and one dao using one jdbc connection to the first warehouse and 3 separate DAOs using JDBC connections to the second warehouse. I have service objects which need to pass hibernate entities to the warehouse daos so that they can construct the correct SQL statements for building reports, so many of my service objects receive a reference to several hibernate DAOs as well as at least one jdbc dao. It works like a charm. All transactions are declared on service object methods, so transactions automatically encapsulate access to every database used by the service method, and my daos don't need to know a thing about transactions. Honestly, I can't imagine a system of this complexity having a simpler interface since everything is done declaratively within the spring application context. There's not a single line of code devoted to dealing with multiple databases. --sam --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
