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From "Niels Beekman" <ni...@wis.nl>
Subject RE: Calling DAO within TypeHandlerCallback
Date Fri, 03 Jun 2005 08:37:20 GMT
Yes, but they are not separate, I think the following happens:

MyDao
	getObject()
		startTransaction()
       		MyTypeHandlerCallBack.getResult()
       			MyOtherDao.getOtherObject()
       				startTransaction() - state is already active, continue
					// process OtherObject
	       			commitTransaction() - commits the transaction
      	 			endTransaction() - closes the resultset / statement
			GetSomeMoreProperties() - throws an exception, resultset is already closed
		commitTransaction()
		endTransaction()

All calls to a DAO are wrapped in a DaoProxy which takes care of the autocommit-behaviour,
if you call a DAO within a DAO (via typehandlers), commitTransaction() is called on the DaoContext,
which is the same for both DAO's.

To make this work properly, autocommit should happen on separate contexts, or commitTransaction()
should implement some kind of "transaction-depth" i.e. nested transactions.

Hopefully this clarifies a bit.

Niels

________________________________________
From: Clinton Begin [mailto:clinton.begin@gmail.com] 
Sent: donderdag 2 juni 2005 0:20
To: ibatis-user-java@incubator.apache.org
Subject: Re: Calling DAO within TypeHandlerCallback


No, but now that you've explained that, it makes sense.  With autocommit, you'll get a separate
transaction for each call (which makes sense for that semantic).

This might make a great FAQ entry.

Clinton

On 5/31/05, Niels Beekman <niels@wis.nl> wrote:
Update:

Strange, when I do not use autocommit-semantics and explicitly demarcate my transactions,
everything goes fine. Well, at least I have a workaround.

Until now, I used autocommit-semantics for most of my reads, and only explicitly demarcated
when updating/inserting/deleting, should I always use the latter, even for reads?

Niels
________________________________________
From: Clinton Begin [mailto:clinton.begin@gmail.com]
Sent: dinsdag 31 mei 2005 17:46 
To: ibatis-user-java@incubator.apache.org
Subject: Re: Calling DAO within TypeHandlerCallback


DAOs never touch result sets. So I wonder what you mean by that? Similarly, iBATIS only closes
result sets once all columns have been iterated through (and hence all TypeHandlers have been
executed). Unfortunately some drivers (like IBM's DB2 driver) like to close resultsets automatically
when the last row is read....you're using JTDS, which we've also had a lot of troubling reports
about. Just for giggles, can you try either the Microsoft driver or the Sybase driver, depending
on which database you're using?

Cheers,
Clinton

On 5/31/05, Niels Beekman <niels@wis.nl> wrote:
Hi, me again :)

When using a TypeHandlerCallback-implementation that calls the DAO, any 
subsequent property that iBATIS tries to fetch results in the following
error (this dump occurred with a Date-property):

java.sql.SQLException: Invalid state, the ResultSet object is closed.
at
net.sourceforge.jtds.jdbc.JtdsResultSet.checkOpen (JtdsResultSet.java:284
)
at
net.sourceforge.jtds.jdbc.JtdsResultSet.findColumn (JtdsResultSet.java:86
4)
at
net.sourceforge.jtds.jdbc.JtdsResultSet.getTimestamp(JtdsResultSet.java:
1225)
at
org.apache.commons.dbcp.DelegatingResultSet.getTimestamp (DelegatingResul
tSet.java:261)
at
com.ibatis.sqlmap.engine.type.DateTypeHandler.getResult(DateTypeHandler.
java:44)
at
com.ibatis.sqlmap.engine.mapping.result.BasicResultMap.getPrimitiveResul
tMappingValue( BasicResultMap.java:544)
at
com.ibatis.sqlmap.engine.mapping.result.BasicResultMap.getResults(BasicR
esultMap.java:303)
at
com.ibatis.sqlmap.engine.execution.SqlExecutor.handleResults(SqlExecutor
.java:363) 
at
com.ibatis.sqlmap.engine.execution.SqlExecutor.executeQuery(SqlExecutor.
java:184)
at
com.ibatis.sqlmap.engine.mapping.statement.GeneralStatement.sqlExecuteQu
ery(GeneralStatement.java :205)
at
com.ibatis.sqlmap.engine.mapping.statement.GeneralStatement.executeQuery
WithCallback(GeneralStatement.java:173)
at
com.ibatis.sqlmap.engine.mapping.statement.GeneralStatement.executeQuery
ForObject(GeneralStatement.java :104)
at
com.ibatis.sqlmap.engine.impl.SqlMapExecutorDelegate.queryForObject(SqlM
apExecutorDelegate.java:561)
at
com.ibatis.sqlmap.engine.impl.SqlMapExecutorDelegate.queryForObject (SqlM
apExecutorDelegate.java :536)
at
com.ibatis.sqlmap.engine.impl.SqlMapSessionImpl.queryForObject(SqlMapSes
sionImpl.java:97)
at
com.ibatis.sqlmap.engine.impl.SqlMapClientImpl.queryForObject (SqlMapClie
ntImpl.java:70)
at
com.ibatis.dao.client.template.SqlMapDaoTemplate.queryForObject (SqlMapDa
oTemplate.java:162)
at
nl.wis.services.dao.impl.sqlmap.SqlMapBaseDaoTemplate.queryForObject (Sql
MapBaseDaoTemplate.java:120)
at <snip>

When just constructing objects within the handler (as stated in FAQ), 
all goes well. I tried to do some debugging and it seems that the inner
DAO-call disposes the resultset, which would obviously result in the
stated error, but I'm not sure this is the case.

I really like the typehandlers, so hopefully this can be resolved... 

Thanks again,

Niels



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