Session s = ...;
Connection c = s.connection();
PS stmnt = c.prepareStatement( ... );
RS rs = stmnt.executeQuery();
s.load( ... );
rs.next();
...
Seems harmless enough, right? Will it work? Answer: well it depends ;)
Both the ConnectionProvider being used and the connection release mode
configured play parts in this (which is a PIA to explain and even more
so to justify). This is exactly the scenario which forced me to add the
notion of BorrowedConnectionProxy to the core as it is now in the first
place, so that the behavior could be consistent; the downside is that it
essentially overrides *any* connection releasing.
ah yes - it comes down to the release mode. Now I remember.
so should we start by @deprecate connection() in 3.2 ?
We don't really have any other portable way of exposing the connection
running the same tx as the session.
If you as a user are doing some work with the connection obtained from a
Hibernate Session, how big of a disruption is it to change from that
usage pattern to this new usage pattern. And whether than disruption is
then adequately offset by any advantages of this new usage pattern.
Yes, and for the usecase of simply getting a connection and do a "one-off"
task
the change is not a big deal.
The issue comes when you are in the scenario of having mixed Hibernate and
JDBC code;
here getting access to a shared connection is good (session.connection()
is one, openSession(connection) is another and ConnectionProvider is a
third)
But I would argue all three are relevant, but I would also be completely
fine
by giving those who want to have "unbounded" access a bigger burden ..e.g.
remembering to close the connection,
live with releasemode being circumvented etc.
The advantages are the typical "avoid tedious error handling", "avoid
redundant resource management", blah-blah-blah you heard from every
other library supporting delegation/templating solutions to JDBC access.
Additionally, you get integration with our notion of connection release
modes, exception conversion, logging, etc. Some of those "extras" could
be achieved even via exposing the proxy rather than the "raw"
connection, but the connection release modes are explicitly
circumvented...
I don't talk against having the new thing exposed, fine by me.
I just think there still is a important "niche" usage for
session.connection(). (not forgetting many books, training, examples,
applications that refers to this method)
On that note:
Will the following snippet be equal to c = session.connection() ?
final Connection[] c = new Connection[1];
session.doWork(
new Work() {
public void performWork(Workspace workspace) {
c[0] = workspace.getConnection();
}
}
);
/max
-----Original Message-----
From: Max Andersen
Sent: Wednesday, August 30, 2006 9:09 AM
To: Steve Ebersole
Cc: hibernate-dev@lists.jboss.org
Subject: Re: [hibernate-dev] Connection proxying
However, removing that connection() method does additionally create an
issue in regards to how to then deal with the common usage pattern of
"subordinate sessions": sf.openSession( s.connection() )... One
thought
was to add either a sf.openSubordinateSession( s ) or even
s.openSubordinateSession()
and...
openSubordinateSession(Interceptor)
openSubordinateStatelessSession()
its a loong name...and isn't the session one gets from getSession a more
true
"subordinate" ?
Needs a better name....or maybe just keep session.connection() around ?
:)
What are the arguments *against* session.connection() if you do the
proxying you
are suggesting ?
/max
-----Original Message-----
From: Max Andersen
Sent: Wednesday, August 30, 2006 2:30 AM
To: Steve Ebersole; hibernate-dev@lists.jboss.org
Subject: Re: [hibernate-dev] Connection proxying
Since the intention is to provide a safer execution for the user then
+1,
but if you are going to do this then i guess session.connection() will
still be ok
since it will just be proxied.
btw. your example is a bit simplified since when hibernate runs inside
an
appserver
the user will normally also have to cast through the appservers
"proxying".
( ( OracleConnection ) (( AppServerConnection ) ( HibernateConnection
)
connection ).getWrappedConnection()
).getNativeConnection()).doSomethingOracleSpecific()
...but I guess we will then soon see NativeJdbcExtractorAdapter
implementation for Hibernate ;)
/max
This is in regards to the JDBC interaction code I recently committed
into the sandbox in SVN.
I am considering proxying the JDBC connections specifically for the
purpose of auto-registering "subordinate objects" (result sets and
statements) for automatic cleanup. Currently the registration is a
manual process in order to take advantage of the automatic cleanup
(have
a look at org.hibernate.jdbc4.jdbc.impl.BasicWorkTest for the basic
usage pattern). Specifically what I am thinking is taking a page
from
how app servers implement Connection handles in relation to data
sources:
public interface HibernateConnection extends java.sql.Connection {
public Connection getWrappedConnection();
}
Of course this makes it more difficult for anyone depending on
casting
to a particular driver's Connection impl at some point. But,
considering that this is atypical usage, my thought was to treat it
as
the more complex use-case; and since this generally requires casting
anyway, one extra cast and "extraction" is not that big of a deal to
me.
For example, to get an oracle connection (for LOB handling for
example):
( ( OracleConnection ) connection ).doSomethingOracleSpecific() -> (
(
OracleConnection ) ( ( HibernateConnection ) connection
).getWrappedConnection() ).doSomethingOracleSpecific()
Plus, would potentially allow for some other niceties like automatic
statement logging (perhaps even with parameter replacement).
Thoughts?
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--
Max Rydahl Andersen
callto://max.rydahl.andersen
Hibernate
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