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From "Louis Letourneau (JIRA)" <ibatis-...@incubator.apache.org>
Subject [jira] Created: (IBATISNET-102) Calling OpenConnection on a DaoManager in different threads causes an Exception
Date Thu, 11 Aug 2005 21:56:54 GMT
Calling OpenConnection on a DaoManager in different threads causes an Exception
-------------------------------------------------------------------------------

         Key: IBATISNET-102
         URL: http://issues.apache.org/jira/browse/IBATISNET-102
     Project: iBatis for .NET
        Type: Bug
  Components: DataAccess  
    Versions: DataAccess 1.6.0, DataAccess 1.6.1    
 Environment: windows xp sp2, .Net 1.1 sp1
    Reporter: Louis Letourneau


Opening many (different)connections each in a seperate thread (as would occur in a web application)
for one instance of a DaoManager causes connection already opened exceptions (or calling CloseConnection
in the same circumstances causes connection already closed exceptions) . It's as if the new
sessions don't get created individually for each thread...

I took the liberty of checking the source code of the DataAccess component, and the variable
_localSqlMapSession in WindowSessionContainer.cs should be static. If it's not the ThreadStatic
attribute will have no effect and every thread will have the same session (as in my case).
(The java ThreadLocal object can be used on a non-static field. The ThreadStatic attribute
cannot. The compiler ignores the attribute on non-static fields).

Exception:
Got: IBatisNet.DataAccess.Exceptions.DataAccessException: DaoManager could not invoke OpenConnection().
A connection is already started. Call CloseConnection first.

I think that if you wish to have the same behaviour as the java dao implementation (having
multiple DaoManager instances that each have different sessions per thread) adding the static
modifier to the ThreadStatic field will not fix the issue in WindowSessionContainer.cs.

Instead of the static ThreadStatic field(which will be shared by every WindowSessionContainer
in a given thread), maybe a hashtable instance that has the current daomanager name as key
and the session as value would work.

ie(WindowSessionContainer.cs) Replace:
------------------------------------------------
[ThreadStatic] 
private 'static' IDalSession _localSqlMapSession = null; // currently missing the static modifier
here

public IDalSession LocalSession
{
	get
	{
		return _localSqlMapSession;
	}
}

public void Store(IDalSession session)
{
	_localSqlMapSession = session;
}
------------------------------------------------
by
------------------------------------------------
[ThreadStatic] 
private static IDictionary _localSqlMapSessions; // can't initialize ThreadStatic variables.
private static Object _mutex = new Object();
private string _daoManagerName;

public WindowSessionContainer(string daoManagerName) {
	lock(_mutex) {
		if(_localSqlMapSessions == null)
			_localSqlMapSessions = new Hashtable();
	}
	_daoManagerName = daoManagerName;
}

public IDalSession LocalSession
{
	get
	{
		return _localSqlMapSessions[_daoManagerName];
	}
}

public void Store(IDalSession session)
{
	_localSqlMapSessions[_daoManagerName] = session;
}
------------------------------------------------

This way, for a given thread, every WindowSessionContainer will share the _localSqlMapSessions,
but since there is one WindowSessionContainer per DaoManager, the IDalSession will be unique
by thread+DaoManager instance. And as a bonus, when the thread dies, the resources will be
cleaned up.


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