Re: [castor-dev] New datasource interface (was: Working with Castor's internal JDBC connection)

Ralf Joachim Wed, 15 Sep 2004 03:33:36 -0700


Hallo Bruce,

thanks for your answer and it is good to know that castor supports connections to more than 1 database.

With the previous mail I also wanted to present an idea for an improvement. I'll give it another try.

Let us assume we have 2 databases A and B, where AObject's are stored in A and BObject's in B. With many database support of castor the code to load an AObject and a BObject would look like:

JDO ajdo = new JDO();
ajdo.setConfiguration( "database.xml" );
ajdo.setDatabaseName( "A" );
Database adb = ajdo.getDatabase();
adb.begin();
AObject a = (AObject)adb.load(AObject.class, aid);
adb.commit();
adb.close();

JDO bjdo = new JDO();
bjdo.setConfiguration( "database.xml" );
bjdo.setDatabaseName( "B" );
Database bdb = bjdo.getDatabase();
bdb.begin();
BObject b = (BObject)bdb.load(BObject.class, bid);
bdb.commit();
bdb.close();

Wouldn't it be nice if castor can deside from database.xml and the mapping included in it from which real database to load the object. With this feature the code to load above 2 objects would look something like:

JDO jdo = new JDO();

// database.xml defines connections to databases A and B
jdo.setConfiguration( "database.xml" );

// get an abstract database object without connection to a real database
Database db = jdo.getDatabase();

// Start transaction
db.begin();

// create connection to database A includes it in the transaction and loads AObject AObject a = (AObject)db.load(AObject.class, aid);

// creates connection to database B includes it in the transaction and loads BObject BObject b = (BObject)db.load(BObject.class, bid);

// commit to both databases
db.commit();
db.close();

Hope this example makes the idea more clear to you.

Regards
Ralf

----- Original Message ----- From: "Bruce Snyder" <[EMAIL PROTECTED]> To: "Castor" <[EMAIL PROTECTED]> Sent: Wednesday, September 15, 2004 10:15 AM Subject: Re: [castor-dev] New datasource interface (was: Working with Castor's internal JDBC connection)

Ralf Joachim wrote:
I thougth it may be better to start a new tread for discussion on new Datasource interface. I appended the Datasource part of the original mail below.
I was going to do the same thing ;-).
As I do not know how you think the new interface should look like and if there are that much differences to the old Database interface my question may be stupid, but isn't it possible that the RelationalDataSourceImpl also implements the Database interface. If this would be possible we can get both interfaces work in parallel and therefor get a migration to the new interface step by step?
I was speaking with a friend about this today. On my ride home today I was thinking that maybe we could shoehorn it in to the TRUNK somehow.

Until now I only used castor to connect to a single database. For the future I also need to connect to more then one database and I don't know if this is posible with castor at the moment. If it is possible with the current castor implementation I will need a connection to Database A to e.g. load a AJDO and a connection to Database B to load BJDO. Wouldn't it be interesting to get a single Database object that desides according to the configuration and mapping to load AJDO from Database A and BJDO from Database B?
Up until April of this year, Castor could connect to as many databases as you want by using many <database> elements in the database/jdo-conf descriptor. But this functionality was broken and has a patch pending here:
    http://bugzilla.exolab.org/show_bug.cgi?id=1594
I've been thinking about creating a new interface model like so:
                +-------------+
                | DataSource |
                +-------------+
                      #
                      |
         +------------+------------+
         |                                      |
+------------------------+   +----------------+
| RelationalDataSource |   | LdapDataSource |
+------------------------+   +----------------+
          .                                           .
        /_\                                        /_\
          |                                            |
          |                                            |
+------------------------------+   +------------------------+
| RelationalDataSourceImpl |     | LdapDataSourceImpl |
+------------------------------+   +------------------------+
For a description of this ASCII UML, please see the following doc:
   http://c2.com/cgi/wiki?UmlAsciiArt
In the diagram above, the DataSource interface would replace the
current Database interface. The second layer allows any additional
DataSource type to be added (JCA connectors to AS/400, etc.). The
third layer is a replacemet for the current DatabaseImpl.
Bear in mind that changes this significant would not go into the
TRUNK. We'd need to create a 1_0 or 2_0 branch for it. With the big
changes we're thinking about, we need to leave the TRUNK alone and
only do minor changes and bugs fixes.
Bruce -- perl -e 'print unpack("u30","<0G)[EMAIL PROTECTED]&5R\\"F9E<G)E=\\$\\!F<FEI+F-O;0\\`\\`");'
The Castor Project
http://www.castor.org/
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http://incubator.apache.org/projects/geronimo.html
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Re: [castor-dev] New datasource interface (was: Working with Castor's internal JDBC connection)

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