You are viewing a plain text version of this content. The canonical link for it is here.
Posted to dev@lucene.apache.org by Daniel Shane <sh...@LEXUM.UMontreal.CA> on 2009/09/10 16:05:57 UTC
LowerCaseFilter, is there a reason why the class is final?
Hi all,
I was wondering why the LowerCaseFilter is declared final? In my code, I
would like to extend it but apparently its not possible. I'm just
wondering why extending this type of class is considered evil?
Daniel Shane
---------------------------------------------------------------------
To unsubscribe, e-mail: java-dev-unsubscribe@lucene.apache.org
For additional commands, e-mail: java-dev-help@lucene.apache.org
RE: LowerCaseFilter, is there a reason why the class is final?
Posted by Uwe Schindler <uw...@thetaphi.de>.
I forget, this known as "Decorator Pattern":
http://en.wikipedia.org/wiki/Decorator_pattern
-----
Uwe Schindler
H.-H.-Meier-Allee 63, D-28213 Bremen
http://www.thetaphi.de
eMail: uwe@thetaphi.de
> -----Original Message-----
> From: Uwe Schindler [mailto:uwe@thetaphi.de]
> Sent: Thursday, September 10, 2009 4:09 PM
> To: java-dev@lucene.apache.org
> Subject: RE: LowerCaseFilter, is there a reason why the class is final?
>
> See https://issues.apache.org/jira/browse/LUCENE-1753
>
> In general, if you want to add functionality plug another filter into the
> chain. At least the implementations should be final (next/incrementToken).
>
> -----
> Uwe Schindler
> H.-H.-Meier-Allee 63, D-28213 Bremen
> http://www.thetaphi.de
> eMail: uwe@thetaphi.de
>
>
> > -----Original Message-----
> > From: Daniel Shane [mailto:shaned@LEXUM.UMontreal.CA]
> > Sent: Thursday, September 10, 2009 4:06 PM
> > To: java-dev@lucene.apache.org
> > Subject: LowerCaseFilter, is there a reason why the class is final?
> >
> > Hi all,
> >
> > I was wondering why the LowerCaseFilter is declared final? In my code, I
> > would like to extend it but apparently its not possible. I'm just
> > wondering why extending this type of class is considered evil?
> >
> > Daniel Shane
> >
> > ---------------------------------------------------------------------
> > To unsubscribe, e-mail: java-dev-unsubscribe@lucene.apache.org
> > For additional commands, e-mail: java-dev-help@lucene.apache.org
>
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: java-dev-unsubscribe@lucene.apache.org
> For additional commands, e-mail: java-dev-help@lucene.apache.org
---------------------------------------------------------------------
To unsubscribe, e-mail: java-dev-unsubscribe@lucene.apache.org
For additional commands, e-mail: java-dev-help@lucene.apache.org
Re: LowerCaseFilter, is there a reason why the class is final?
Posted by Ted Dunning <te...@gmail.com>.
Lucene has always had way too much use of final for my taste. I have often
had to resort of chicanery to get around this.
In many cases, there wasn't even an alternative abstract class. Writing
test cases involving IndexWriters was a case that sticks in my memory.
On Fri, Sep 11, 2009 at 7:13 AM, Mark Miller <ma...@gmail.com> wrote:
> I think thats true - but its also interesting to note: LowerCaseFilter
> has been final since it was put into svn in 01.
>
--
Ted Dunning, CTO
DeepDyve
Re: LowerCaseFilter, is there a reason why the class is final?
Posted by Mark Miller <ma...@gmail.com>.
I think thats true - but its also interesting to note: LowerCaseFilter
has been final since it was put into svn in 01.
--
- Mark
http://www.lucidimagination.com
Ted Dunning wrote:
>
> Copy/paste. Clearly Uwe and others were worried that users wouldn't
> be able to extend these classes compatibly.
>
> My own opinion is that this causes worse problems with back
> compatibility because people wind up copying code instead of calling
> it. You may be able to extend an abstract class to minimize your work.
>
> On Fri, Sep 11, 2009 at 5:33 AM, Daniel Shane
> <shaned@lexum.umontreal.ca <ma...@lexum.umontreal.ca>> wrote:
>
> Does anyone else see a way of doing this that is simple?
>
>
>
>
> --
> Ted Dunning, CTO
> DeepDyve
>
---------------------------------------------------------------------
To unsubscribe, e-mail: java-dev-unsubscribe@lucene.apache.org
For additional commands, e-mail: java-dev-help@lucene.apache.org
Re: LowerCaseFilter, is there a reason why the class is final?
Posted by Daniel Shane <sh...@LEXUM.UMontreal.CA>.
IMHO, if I'm forced to write a by-pass filter to re-use a filter instead
of copy/pasting it, I think we are getting way off the Decorator
Pattern. Its not simple anymore. I bet you have 9 chances out of 10 that
a dev. will copy/paste that code before writing a by-pass filter.
Extending the functionality of a filter should not be something
difficult. And having everyone write their own bypass filter seems
really annoying. Imagine all those people having to write the by-pass
filter.
We should include such a filter in Lucene natively and add in the
JavaDocs of the filter the mention that you can extend them with it to
avoid people copy/pasting code.
If you want I can cook up a draft to get things started.
Daniel Shane
Ted Dunning wrote:
>
> Copy/paste. Clearly Uwe and others were worried that users wouldn't
> be able to extend these classes compatibly.
>
> My own opinion is that this causes worse problems with back
> compatibility because people wind up copying code instead of calling
> it. You may be able to extend an abstract class to minimize your work.
>
> On Fri, Sep 11, 2009 at 5:33 AM, Daniel Shane
> <shaned@lexum.umontreal.ca <ma...@lexum.umontreal.ca>> wrote:
>
> Does anyone else see a way of doing this that is simple?
>
>
>
>
> --
> Ted Dunning, CTO
> DeepDyve
>
Re: LowerCaseFilter, is there a reason why the class is final?
Posted by Ted Dunning <te...@gmail.com>.
Copy/paste. Clearly Uwe and others were worried that users wouldn't be able
to extend these classes compatibly.
My own opinion is that this causes worse problems with back compatibility
because people wind up copying code instead of calling it. You may be able
to extend an abstract class to minimize your work.
On Fri, Sep 11, 2009 at 5:33 AM, Daniel Shane <sh...@lexum.umontreal.ca>wrote:
> Does anyone else see a way of doing this that is simple?
--
Ted Dunning, CTO
DeepDyve
RE: LowerCaseFilter, is there a reason why the class is final?
Posted by Uwe Schindler <uw...@thetaphi.de>.
> The only thing I can do is add a filter before the LowerCaseFilter that
> would pass all the non-word tokens to the next filter, but it seems really
> complicated for a case where a simple extend would do the job.
This is the way to go!
Uwe
---------------------------------------------------------------------
To unsubscribe, e-mail: java-dev-unsubscribe@lucene.apache.org
For additional commands, e-mail: java-dev-help@lucene.apache.org
Re: LowerCaseFilter, is there a reason why the class is final?
Posted by Daniel Shane <sh...@LEXUM.UMontreal.CA>.
With the current API of TokenStream (incrementToken) I really do not see
how I could do the following scenario with the Decorator Pattern :
I have a case where I would like to execute the LowerCaseFilter only if
the token is of type "word". I do not want to execute the
LowerCaseFilter if the token is of type "number" for example.
Unfortunately, I don't see how this is possible using the current API
and the fact that the filters are final.
The only thing I can do is add a filter before the LowerCaseFilter that
would pass all the non-word tokens to the next filter, but it seems
really complicated for a case where a simple extend would do the job.
Or, if the API had two methods, one which increments the stream and
another which process the current "token" or attributes then it would be
possible to do what I have in mind using the Decorator Pattern.
Does anyone else see a way of doing this that is simple?
Daniel Shane
Uwe Schindler wrote:
> See https://issues.apache.org/jira/browse/LUCENE-1753
>
> In general, if you want to add functionality plug another filter into the
> chain. At least the implementations should be final (next/incrementToken).
>
> -----
> Uwe Schindler
> H.-H.-Meier-Allee 63, D-28213 Bremen
> http://www.thetaphi.de
> eMail: uwe@thetaphi.de
>
>
>
>> -----Original Message-----
>> From: Daniel Shane [mailto:shaned@LEXUM.UMontreal.CA]
>> Sent: Thursday, September 10, 2009 4:06 PM
>> To: java-dev@lucene.apache.org
>> Subject: LowerCaseFilter, is there a reason why the class is final?
>>
>> Hi all,
>>
>> I was wondering why the LowerCaseFilter is declared final? In my code, I
>> would like to extend it but apparently its not possible. I'm just
>> wondering why extending this type of class is considered evil?
>>
>> Daniel Shane
>>
>> ---------------------------------------------------------------------
>> To unsubscribe, e-mail: java-dev-unsubscribe@lucene.apache.org
>> For additional commands, e-mail: java-dev-help@lucene.apache.org
>>
>
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: java-dev-unsubscribe@lucene.apache.org
> For additional commands, e-mail: java-dev-help@lucene.apache.org
>
>
RE: LowerCaseFilter, is there a reason why the class is final?
Posted by Uwe Schindler <uw...@thetaphi.de>.
See https://issues.apache.org/jira/browse/LUCENE-1753
In general, if you want to add functionality plug another filter into the
chain. At least the implementations should be final (next/incrementToken).
-----
Uwe Schindler
H.-H.-Meier-Allee 63, D-28213 Bremen
http://www.thetaphi.de
eMail: uwe@thetaphi.de
> -----Original Message-----
> From: Daniel Shane [mailto:shaned@LEXUM.UMontreal.CA]
> Sent: Thursday, September 10, 2009 4:06 PM
> To: java-dev@lucene.apache.org
> Subject: LowerCaseFilter, is there a reason why the class is final?
>
> Hi all,
>
> I was wondering why the LowerCaseFilter is declared final? In my code, I
> would like to extend it but apparently its not possible. I'm just
> wondering why extending this type of class is considered evil?
>
> Daniel Shane
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: java-dev-unsubscribe@lucene.apache.org
> For additional commands, e-mail: java-dev-help@lucene.apache.org
---------------------------------------------------------------------
To unsubscribe, e-mail: java-dev-unsubscribe@lucene.apache.org
For additional commands, e-mail: java-dev-help@lucene.apache.org