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From Edwin Lee <edwin11_1...@yahoo.com.sg>
Subject Re: ClassCastException when writing to index writer
Date Tue, 07 Oct 2008 04:34:06 GMT
Hi Paul,

now i'm curious to know how the overriden java.util.Vector implements the clone
method. Any chance of posting a snippet? ;)



Cheers,
Edwin



--- Paul Chan <wayofdragon@gmail.com> wrote:

> Seems like I found the culprit to the problem.  Because I am using
> Terracotta to doing JVM clustering, it has overriden many classes of
> java.util.*.  If I take out Terracotta from my configuration, then I don't
> get the ClassCastException problem any longer.  I will talk to the
> Terracotta folks to see if I have done something wrong on my end.
> 
> Thanks again for everyone's help!
> 
> On Mon, Oct 6, 2008 at 12:26 PM, Paul Chan <wayofdragon@gmail.com> wrote:
> 
> > Hi Edwin,
> >
> > Yes, I am running the TestVector against the same class path as my actual
> > application.  My class path contains the Lucene JAR files.  This is very
> > bizzard because my TestVector class extends Vector and it works, but for
> > some reason SegmentInfos also extends Vector but it doesnt work.
> > I did some more investigation and I found the following:
> >
> > final class SegmentInfos extends Vector
> > {
> >    public Object clone() {
> >       Object a = super.clone(); --> code that I added to do some debug
> >      SegmentInfos sis = (SegmentInfos) a;
> >      ...
> >    }
> > }
> >
> > When super.clone() returns, it actually returns a Vector object instead of
> > a SegmentInfos object against my expectation so that explains why the
> > ClassCastException occurs.  On the other hand, when I run my TestVector
> > class:
> >
> > final class TestVector extends Vector
> > {
> >    public Object clone() {
> >       Object a = super.clone(); --> code that I added to do some debug
> >       TestVector sis = (TestVector) a;
> >      ...
> >    }
> > }
> >
> > When super.clone() returns, it returns TestVector!
> >
> > This tells me that there is something wrong with Lucene build file that
> > causes this problem, but I have no idea what it could be.  In Lucene's
> > common-build.xml, I changed the 1.4 properties to 1.6 propreties but still
> > to no avail.
> >
> >
> >
> > On Mon, Oct 6, 2008 at 12:04 PM, Edwin Lee
> <edwin11_1979@yahoo.com.sg>wrote:
> >
> >> Hi Paul,
> >>
> >> When you say that your dummy TestVector class works, are you running it
> >> using
> >> the same classpaths that you used to run your actual application? Does it
> >> contain the Lucene JAR files?
> >>
> >>
> >>
> >> Regards,
> >> Edwin
> >>
> >>
> >>
> >> --- Paul Chan <wayofdragon@gmail.com> wrote:
> >>
> >> > I have tried to recompile Lucene 2.3.2 under my environment (SUN JDK
> >> 1.6)
> >> > and it still doesn't work.  I am beginning to think that maybe there is
> >> > something wrong with lucene's build script.  My TestVector class's
> >> clone()
> >> > method works without a hitch, but SegmentInfos' clone() method doesnt
> >> work
> >> > at all.  I don't really know what to do at this moment.  Does anyone
> >> have
> >> > any insight?
> >> >
> >> > On Sun, Oct 5, 2008 at 10:45 PM, Paul Chan <wayofdragon@gmail.com>
> >> wrote:
> >> >
> >> > > Thank you all for your input.  However, this is what I have discovered
> >> so
> >> > > far:
> >> > >
> >> > >    - I tried running the test that Edwin suggested and it failed for
> >> me in
> >> > >    my environment (Lucene 2.3.2, Windows XP, SUN JDK 1.5 or 1.6)
> >> > >
> >> > > e.g. SegmentInfos sis = new SegmentInfos();
> >> > >       SegmentInfos sis2 = (SegmentInfos) sis.clone();
> >> > >
> >> > >    - Interestingly, I tried to create a dummy test class which mimics
> >> > >    SegmentInfos as follows and it works!:
> >> > >
> >> > > public class TestVector extends Vector
> >> > > {
> >> > >    public TestVector clone()
> >> > >    {
> >> > >       TestVector cl = (TestVector)super.clone();
> >> > >       return cl;
> >> > >    }
> >> > > }
> >> > >
> >> > >          TestVector vector = new TestVector();
> >> > >          TestVector vClone = (TestVector)vector.clone();
> >> > >
> >> > >    - This tells me that perhaps there is something wrong with the
> >> lucene
> >> > >    package that I have downloaded (some sort of incompatibility?).
 I
> >> will
> >> > try
> >> > >    to recompile the lucene package in my own environment and see if
I
> >> can
> >> > fix
> >> > >    the problem.
> >> > >
> >> > >
> >> > > On Sat, Oct 4, 2008 at 2:21 AM, Edwin Lee <edwin11_1979@yahoo.com.sg
> >> >wrote:
> >> > >
> >> > >> i think, very likely, you have another copy of java.util.Vector
> >> loaded,
> >> > >> and
> >> > >> this one tries to be too clever with its implementation of clone
> >> > >> (instantiate a
> >> > >> new Vector instance) instead of delegating to its super class
> >> (Object).
> >> > >>
> >> > >>
> >> > >>
> >> > >> HTH,
> >> > >> Edwin
> >> > >>
> >> > >>
> >> > >>
> >> > >> --- Chris Hostetter <hossman_lucene@fucit.org> wrote:
> >> > >>
> >> > >> >
> >> > >> > :        SegmentInfos sis = (SegmentInfos) super.clone();
> >> > >> >
> >> > >> > : We see that it is trying to cast a Vector into SegmentInfos
which
> >> > >> explains
> >> > >> > : the ClassCastException.  This is definitely a bug.
> >> > >> >
> >> > >> > I'm really not sure how you could be getting that
> >> ClassCastException
> >> > >> > unless there's a really horrific bug in the JRE you are using.
> >> > >> >
> >> > >> > You'll see this in just about every (non-trivial) use of
> >> super.clone()
> >> > >> ...
> >> > >>
> >> > >>
> >> > >>
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> >> > >>
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> >> > >>
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> >> > >
> >> >
> >>
> >>
> >>
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> 



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