[OJB-developers] Re: Named Root Objects
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[OJB-developers] Re: Named Root Objects
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From: Thomas M. <tho...@ho...> - 2002-01-09 17:51:18
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Hi again,
Michael Nowotny wrote:
> Hi Thomas!
>
> Thanks for the illustration. Binding collections works fine for me now!
> The reason why my earlier attempt failed was that I was still using
> InstantDB.It seems that some transactions got only halfway commited due to
> program termination following db.close(). Now I'm using Hypersonic and
> everything works.
>
Fine !
> During the course of setting up a test procedure I came across some strange
> behaviour. The following code snipped throws an ObjectNameNotBoundException.
>
> // fails:
> tx = odmg.newTransaction();
> tx.begin();
> db.bind(odmg.newDList(), "MyList");
> db.unbind("MyList");
> db.bind(odmg.newDList(), "MyList");
> // DList list = (DList)db.lookup("MyList");
> tx.commit();
>
> tx = odmg.newTransaction();
> tx.begin();
> DList newList = (DList)db.lookup("MyList");
> tx.commit();
>
> Binding the same name twice within the same transaction seems to cause an
> error.
Oops, This is a bug. I'll add it to my todo list!
This is not very important though because usually one wouldn't want
> to bind an object to a some name and thereafter unbinding that name withing
> the same transaction.
>
> Another question arose when I had a look at the contents of my database. If
> I add content to my list which is a named root object this content gets
> persistent as well. That's part of persistence by reachability. But when I
> unbind the root object and the content is therefore no longer reachable, it
> doesn't get removed from the database but is still present. Is there any way
> of performing some kind of garbage collection?
>
Currently there is no GC implemented.
IMHO it will be VERY difficult to have a real GC as it would be possible
with an OODBMS.
It will be very difficult to decide if objects can safely be deleted.
BUT: we have been thinking of changing the semantics of DList.remove()
an similar methods as name roots unbind so that removed objects are
deleted from the DB.
Any ideas?
-- Thomas
> Keep up the good work!
>
> Thanks, Michael
>
> ----- Original Message -----
> From: "Thomas Mahler" <tho...@ho...>
> To: "Michael Nowotny" <mic...@gm...>; "ojb"
> <obj...@li...>
> Sent: Tuesday, January 08, 2002 8:20 PM
> Subject: Re: Named Root Objects
>
>
>
>>Hi Michael,
>>
>>please see the attached Java class.
>>
>>You can replace the original version of test.ojb.odmg.OdmgExamples with
>>this new version to have it executed with the OJB JUnit tests.
>>
>>There is a new testMethod testNrmAndDlists that tests your scenario.
>>Works great!
>>
>>HTH,
>>
>>Thomas
>>
>>Michael Nowotny wrote:
>>
>>
>>>Hi Thomas!
>>>
>>>Just found your OJB project on sourceforge. I think it's great to have
>>>
> an
>
>>>open source ODMG implementation around.
>>>Now I've got a question concerning the ODMG implemetation.
>>>Is it possible to use a DList for example as a named root object.
>>>
> Binding
>
>>>that object to a name works but looking it up again causes an
>>>IllegalArgumentException.
>>>
>>>Have you ever tried to bind a Collection. If so, I would be grateful if
>>>
> you
>
>>>could drop me some lines of source code.
>>>
>>>Thanks Michael
>>>
>>>
>>>
>>>
>>>
>>>
>>
>>
>
>
> ----------------------------------------------------------------------------
> ----
>
>
>
>>package test.ojb.odmg;
>>
>>
>>import junit.framework.TestCase;
>>import ojb.broker.Identity;
>>import ojb.broker.PersistenceBroker;
>>import ojb.broker.PersistenceBrokerFactory;
>>import ojb.broker.cache.ObjectCacheFactory;
>>import ojb.odmg.OJB;
>>import ojb.odmg.states.ModificationState;
>>import ojb.odmg.states.StateNewClean;
>>import ojb.odmg.states.StateNewDirty;
>>import org.odmg.*;
>>
>>import java.util.List;
>>
>>/** Demo Application that shows basic concepts for Applications using the
>>
> OJB ODMG
>
>> * implementation as an transactional object server.
>> */
>>public class OdmgExamples extends TestCase
>>{
>> public static void main(String[] args)
>> {
>> String[] arr = {CLASS.getName()};
>> junit.textui.TestRunner.main(arr);
>> }
>>
>> private static Class CLASS = OdmgExamples.class;
>> private String databaseName;
>>
>> /**
>> * Insert the method's description here.
>> * Creation date: (24.12.2000 00:33:40)
>> */
>> public OdmgExamples(String name)
>> {
>> super(name);
>> }
>>
>> /**
>> * Insert the method's description here.
>> * Creation date: (06.12.2000 21:58:53)
>> */
>> public void setUp()
>> {
>> databaseName =
>>
> PersistenceBrokerFactory.getConfiguration().getRepositoryFilename();
>
>>
>> }
>>
>> /**
>> * Insert the method's description here.
>> * Creation date: (06.12.2000 21:59:14)
>> */
>> public void tearDown()
>> {
>> databaseName = null;
>> }
>>
>> /**TestThreadsNLocks state transition of modification states*/
>> public void testModificationStates()
>> {
>> // get facade instance
>> Implementation odmg = OJB.getInstance();
>> Database db = odmg.newDatabase();
>> //open database
>> try
>> {
>> db.open(databaseName, Database.OPEN_READ_WRITE);
>> }
>> catch (ODMGException ex)
>> {
>> fail("ODMGException: " + ex.getMessage());
>> }
>> ModificationState oldState = StateNewClean.getInstance();
>> ModificationState newState = oldState.markDirty();
>> assertEquals(StateNewDirty.getInstance(), newState);
>>
>> oldState = newState;
>> newState = oldState.markDirty();
>> assertEquals(oldState, newState);
>>
>>
>> // close database
>> try
>> {
>> db.close();
>> }
>> catch (ODMGException ex)
>> {
>> fail("ODMGException: " + ex.getMessage());
>> }
>>
>> }
>>
>> public void testOdmgSession()
>> {
>> // get facade instance
>> Implementation odmg = OJB.getInstance();
>> Database db = odmg.newDatabase();
>> //open database
>> try
>> {
>> db.open(databaseName, Database.OPEN_READ_WRITE);
>> }
>> catch (ODMGException ex)
>> {
>> fail("ODMGException: " + ex.getMessage());
>> }
>> Transaction tx = odmg.newTransaction();
>>
>> //perform transaction
>> try
>> {
>> tx.begin();
>>
>> Article example = new Article();
>> example.setArticleId(777);
>> db.makePersistent(example);
>>
>>
>>
>> // modify Object
>> example.setStock(333);
>> example.addToStock(47);
>> example.addToStock(7);
>> example.addToStock(4);
>>
>>
>> //System.out.println("now commit all changes...");
>> tx.commit();
>> }
>> catch (Exception ex)
>> {
>> tx.abort();
>> }
>>
>> // close database
>> try
>> {
>> db.close();
>> }
>> catch (ODMGException ex)
>> {
>> fail("ODMGException: " + ex.getMessage());
>> }
>> }
>>
>> public void testOQLQuery()
>> {
>> // get facade instance
>> Implementation odmg = OJB.getInstance();
>> Database db = odmg.newDatabase();
>> //open database
>> try
>> {
>> db.open(databaseName, Database.OPEN_READ_WRITE);
>> }
>> catch (ODMGException ex)
>> {
>> fail("ODMGException: " + ex.getMessage());
>> }
>> Transaction tx = odmg.newTransaction();
>>
>> //perform transaction
>> try
>> {
>> tx.begin();
>>
>>
>> OQLQuery query = odmg.newOQLQuery();
>> query.create("select anArticle from " +
>>
> Article.class.getName() + " where articleId = 7");
>
>> List results = (List) query.execute();
>>
>> Article a = (Article) results.get(0);
>>
>>
>> // cross check with PersistenceBroker lookup
>> // 1. get OID
>> Article example = new Article();
>> example.setArticleId(7);
>> Identity oid = new Identity(example);
>> // 2. lookup object by OID
>> PersistenceBroker broker = OJB.getInstance().getBroker();
>> broker.clearCache();
>> Article b = (Article) broker.getObjectByIdentity(oid);
>>
>> assertEquals("should be same object", a, b);
>>
>> //System.out.println("now commit all changes...");
>> tx.commit();
>> }
>> catch (Exception ex)
>> {
>> tx.abort();
>> fail("ODMGException: " + ex.getMessage());
>> }
>>
>> // close database
>> try
>> {
>> db.close();
>> }
>> catch (ODMGException ex)
>> {
>> fail("ODMGException: " + ex.getMessage());
>> }
>> }
>>
>> public void testNrmAndDlists()
>> {
>> // get facade instance
>> Implementation odmg = OJB.getInstance();
>> Database db = odmg.newDatabase();
>> //open database
>> try
>> {
>> db.open(databaseName, Database.OPEN_READ_WRITE);
>> }
>> catch (ODMGException ex)
>> {
>> fail("ODMGException: " + ex.getMessage());
>> }
>> Transaction tx = odmg.newTransaction();
>>
>> //perform transaction
>> try
>> {
>> tx.begin();
>>
>>
>> OQLQuery query = odmg.newOQLQuery();
>> query.create("select x from " + Article.class.getName() + "
>>
> where productGroupId = 7");
>
>> DList results = (DList) query.execute();
>>
>>
>> int originalSize = results.size();
>>
>> OJB.getLogger().info(results);
>>
>> String name = "gimme fruits !";
>>
>> db.bind(results, name);
>> tx.commit();
>>
>> // clear the cache to make sure things are loaded from RDBMS !
>> OJB.getInstance().getBroker().clearCache();
>>
>> tx = odmg.newTransaction();
>> tx.begin();
>>
>> // look it up again
>> DList newResults = (DList) db.lookup(name);
>>
>> assertEquals(originalSize,newResults.size());
>> OJB.getLogger().info(results);
>>
>> tx.commit();
>>
>>
>> }
>> catch (Throwable t)
>> {
>> tx.abort();
>> fail("ODMGException: " + t.getMessage());
>> }
>>
>> // close database
>> try
>> {
>> db.close();
>> }
>> catch (ODMGException ex)
>> {
>> fail("ODMGException: " + ex.getMessage());
>> }
>> }
>>
>>
>>
>> public void testOQLQueryBind()
>> {
>> // get facade instance
>> Implementation odmg = OJB.getInstance();
>> Database db = odmg.newDatabase();
>> //open database
>> try
>> {
>> db.open(databaseName, Database.OPEN_READ_WRITE);
>> }
>> catch (ODMGException ex)
>> {
>> fail("ODMGException: " + ex.getMessage());
>> }
>> Transaction tx = odmg.newTransaction();
>>
>> //perform transaction
>> try
>> {
>> tx.begin();
>>
>>
>> OQLQuery query = odmg.newOQLQuery();
>> query.create("select anArticle from " +
>>
> Article.class.getName() + " where articleId = $678");
>
>> query.bind(new Integer(7));
>>
>> List results = (List) query.execute();
>>
>> Article a = (Article) results.get(0);
>>
>> //crosscheck with PersistenceBroker lookup
>> // 1. get OID
>> Article example = new Article();
>> example.setArticleId(7);
>> Identity oid = new Identity(example);
>>
>> ObjectCacheFactory.getObjectCache().clear();
>> // 2. lookup object by OID
>> PersistenceBroker broker = OJB.getInstance().getBroker();
>> broker.clearCache();
>> Article b = (Article) broker.getObjectByIdentity(oid);
>>
>> assertEquals("should be same object", a, b);
>>
>> //System.out.println("now commit all changes...");
>> tx.commit();
>> }
>> catch (Exception ex)
>> {
>> tx.abort();
>> fail("ODMGException: " + ex.getMessage());
>> }
>>
>> // close database
>> try
>> {
>> db.close();
>> }
>> catch (ODMGException ex)
>> {
>> fail("ODMGException: " + ex.getMessage());
>> }
>> }
>>
>> public void tesOQLQueryOnCollections()
>> {
>> // get facade instance
>> Implementation odmg = OJB.getInstance();
>> Database db = odmg.newDatabase();
>> //open database
>> try
>> {
>> db.open(databaseName, Database.OPEN_READ_WRITE);
>> }
>> catch (ODMGException ex)
>> {
>> fail("ODMGException: " + ex.getMessage());
>> }
>> Transaction tx = odmg.newTransaction();
>>
>> //perform transaction
>> try
>> {
>> tx.begin();
>> OQLQuery query = odmg.newOQLQuery();
>> query.create("select aLotOfArticles from " +
>>
> Article.class.getName() + " where productGroupId = 4");
>
>> DCollection results = (DCollection) query.execute();
>> results = results.query("price > 35");
>>
>> // now perform control query
>> query = odmg.newOQLQuery();
>> query.create("select aLotOfArticles from " +
>>
> Article.class.getName() + " where productGroupId = 4 and price > 35");
>
>> DCollection check = (DCollection) query.execute();
>>
>> assertEquals(results, check);
>>
>>
>> tx.commit();
>> }
>> catch (Exception ex)
>> {
>> tx.abort();
>> ex.printStackTrace();
>> fail("ODMGException: " + ex.getMessage());
>> }
>>
>> // close database
>> try
>> {
>> db.close();
>> }
>> catch (ODMGException ex)
>> {
>> fail("ODMGException: " + ex.getMessage());
>> }
>> }
>>
>>
>> /**try to open non-existing db*/
>> public void tesWrongDbName()
>> {
>> // get facade instance
>> OJB objectserver = OJB.getInstance();
>> Database db = objectserver.newDatabase();
>>
>> //try open database with non existing repository file:
>> String wrongDatabaseName = "ThereIsNoSuchFile";
>> try
>> {
>> db.open(wrongDatabaseName, Database.OPEN_READ_WRITE);
>> fail("should not be able to open database " +
>>
> wrongDatabaseName);
>
>> }
>> catch (ODMGException ex)
>> {
>> return;
>> }
>> }
>>}
>>
>>
>
>
>
>
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