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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