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From sebb <seb...@gmail.com>
Subject Re: svn commit: r785552 - in /commons/proper/math/trunk/src: java/org/apache/commons/math/complex/Complex.java site/xdoc/changes.xml
Date Fri, 19 Jun 2009 12:14:44 GMT
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.

The above code might be slightly slower than using reflection (or
maybe not), but it will always work regardless of security managers.

>  Phil
>
>
> > Luc
> >
> >
> >
> > >
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