commons-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Bill Barker" <billwbar...@verizon.net>
Subject Re: svn commit: r785552 - in /commons/proper/math/trunk/src:java/org/apache/commons/math/complex/Complex.javasite/xdoc/changes.xml
Date Sat, 20 Jun 2009 22:58:28 GMT

----- Original Message ----- 
From: "sebb" <sebbaz@gmail.com>
To: "Commons Developers List" <dev@commons.apache.org>
Sent: Saturday, June 20, 2009 4:02 AM
Subject: Re: svn commit: r785552 - in 
/commons/proper/math/trunk/src:java/org/apache/commons/math/complex/Complex.javasite/xdoc/changes.xml


On 20/06/2009, Bill Barker <billwbarker@verizon.net> wrote:
>
>  ----- Original Message ----- From: "sebb" <sebbaz@gmail.com>
>  To: "Commons Developers List" <dev@commons.apache.org>
>  Sent: Friday, June 19, 2009 5:14 AM
>
>  Subject: Re: svn commit: r785552 - in
> /commons/proper/math/trunk/src:java/org/apache/commons/math/complex/Complex.java
> site/xdoc/changes.xml
>
>
>  On 19/06/2009, Phil Steitz <phil.steitz@gmail.com> wrote:
>
> > luc.maisonobe@free.fr wrote:
> >
> > > ----- "Bill Barker" <billwbarker@verizon.net> a écrit :
> > >
> > >
> > >
> > > > ----- Original Message ----- From: <luc.maisonobe@free.fr>
> > > > To: "Commons Developers List" <dev@commons.apache.org>
> > > > Sent: Wednesday, June 17, 2009 2:58 PM
> > > > Subject: Re: svn commit: r785552 - in
> > /commons/proper/math/trunk/src:
> > > >
> > > > java/org/apache/commons/math/complex/Complex.java
> > > > site/xdoc/changes.xml
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > > ----- "Phil Steitz" <phil.steitz@gmail.com> a écrit :
> > > > >
> > > > >
> > > > >
> > > > > > Sorry if I am being dense here. What serialization problem do

> > > > > > the
> > > > > >
> > > > > >
> > > > >
> > > > new
> > > >
> > > >
> > > > >
> > > > > > fields cause, exactly? The class is immutable and they are set

> > > > > > by
> > > > > >
> > > > > >
> > > > >
> > > > the
> > > >
> > > >
> > > > >
> > > > > > constructor.
> > > > > >
> > > > > >
> > > > > It takes more space to store. If someone uses serialization to 
> > > > > store
> > > > >
> > > > >
> > > > or
> > > >
> > > > > send a bunch of complex >this will vastly increase the load.
> > > > >
> > > > >
> > > > The main problem is that the fields can be either transient or 
> > > > final,
> > > > but not both (or rather, you can't reset the value of final fields 
> > > > in
> > readObject).  I have a slight preference for transient for the reason
> > > > Luc gave (a BlockFieldMatrix<ComplexField> will get large quickly),

> > > >  >
> > and
> > > > have no problem doing the change myself.  But I can wait for other
> > opinions.
> > > >
> > >
> > > +1 for that.
> > > You can reset final fields in readObject, with some java.lang.reflect
> > dirty tricks. Look at the DeserializeReal{Vector, Matrix} methods in
> > MatrixUtils.
> > >
> > >
> >
> > >  +1
> > >
> >
> > Complex is not currently a final class, but if there are no use-cases
> > for it to be extended it could be made so, and one could then use the
> > "defensive readResolve" idiom (Effective Java item 57):
> >
> > private Object readResolve(){
> >   return new Complex(real, imaginary);
> > }
> >
> > This would still work even if Complex remained non-final, however
> > sub-classes could potentially subvert the deserialisation by
> > overriding the readResolve. Maybe that is a proce worth paying.
> >
> >
>>
>>  It is about as useful to subclass Complex as it is to subclass Double.
>
>In which case, why not make Complex final?
>

Personally, I have no problem with making it final.  But the existance of 
createComplex seem to point to somebody having a use case to subclass it.

>> But
>> with my recent patch, where the Complex readResolve method is final, but
>> invokes a method than can be overridden in a subclass (but which must 
>> still
>> return a Complex instance), I think that most of the problems would be
>> solved.  As always, comments welcome.
>
>The readResolve() method needs to be protected otherwise subclasses
>will not use it.
>

I'm being dense here.  I thought that ObjectInputStream ignored qualifiers 
on this method.

>The subclass could still subvert the Complex invariants by using the
>overridable createComplex() method to return the deserialised Complex
>instance without setting the transient fields correctly.
>
>I think we'll either have to make the class final, or accept that
>subclasses may be able to subvert it if they try hard enough.
>

Yes, but they have to try pretty hard ;).  At least a half dozen methods 
that use createComplex need to be overridden to have a working subclass.

>But does that matter? There are probably other serializable math
>classes that don't protect themselves.
>

IMHO, it doesn't matter that much.
>>
>>
> > The above code might be slightly slower than using reflection (or
> > maybe not), but it will always work regardless of security managers.
> >
> >
> > >  Phil
> > >
> >
> >
> > > Luc
> > >
> > >
> > >
> > > >
> >
> ---------------------------------------------------------------------
> > > > To unsubscribe, e-mail:
> > dev-unsubscribe@commons.apache.org
> > > > For additional commands, e-mail: dev-help@commons.apache.org
> > > >
> > > >
> > >
> > >
> >
> ---------------------------------------------------------------------
> > > To unsubscribe, e-mail:
> > dev-unsubscribe@commons.apache.org
> > > For additional commands, e-mail: dev-help@commons.apache.org
> > >
> > >
> > >
> >
> >
> >
> ---------------------------------------------------------------------
> >  To unsubscribe, e-mail:
> dev-unsubscribe@commons.apache.org
> >  For additional commands, e-mail: dev-help@commons.apache.org
> >
> >
> >
>
> ---------------------------------------------------------------------
>  To unsubscribe, e-mail: dev-unsubscribe@commons.apache.org
>  For additional commands, e-mail: dev-help@commons.apache.org
>
>
>
> ---------------------------------------------------------------------
>  To unsubscribe, e-mail: dev-unsubscribe@commons.apache.org
>  For additional commands, e-mail: dev-help@commons.apache.org
>
>

---------------------------------------------------------------------
To unsubscribe, e-mail: dev-unsubscribe@commons.apache.org
For additional commands, e-mail: dev-help@commons.apache.org



---------------------------------------------------------------------
To unsubscribe, e-mail: dev-unsubscribe@commons.apache.org
For additional commands, e-mail: dev-help@commons.apache.org


Mime
View raw message