> -----Original Message-----
> From: apache@lucene.com [mailto:apache@lucene.com]
> Sent: Thursday, April 11, 2002 8:00 PM
> To: lucene-user@jakarta.apache.org
> Subject: RE: why is document final
>
>
> > From: Halácsy Péter
> >
> > could someone explain why Document is final?
>
> Because it was not designed to be subclassed.
>
> When I wrote Lucene I only made classes non-final that I
> expected end users
> to need to subclass. In the case of Document, this is
> perhaps overkill, but
> I prefer to have folks try to first use Lucene the way it is
> intended. This
> results in fewer spurious bug reports.
>
IndexWriter is final: I wanted to implement a BatchIndexWriter that adds documents first in a ram directory and after a while adds to a FSDirectory (as you suggested:
http://www.mail-archive.com/lucene-user@jakarta.apache.org/msg00128.html)
Searcher can't be subclassed (from other package than org.apache.lucene.search) because it has package protected abstract methods. I wanted to implement a ManagedSearcher class (something like PooledConnection) that can be used in conjuction with IndexAccessControl (
http://www.mail-archive.com/lucene-dev@jakarta.apache.org/msg00938.html)
> Why do you need to subclass Document?
>
I was wondering if I could make a class representing object of my application that are documents (--> extends Document). For example in the demo app org.apache.lucene.demo.FileDocument is not a Document, only a static factory class. It would be much object oriented to have a FileDocument as
public FileDocument extends Document {
public FileDocument(File file) throws IOException {
add(Field.Text("path", f.getPath()));
add(Field.Keyword("modified",
DateField.timeToString(f.lastModified())));
FileInputStream is = new FileInputStream(f);
Reader reader = new BufferedReader(new InputStreamReader(is));
add(Field.Text("contents", reader));
}
}
On the other hand I can imagine that IndexWriter.addDocument saves the type of Document as ObjectOutputStream does. Example
EmailDocument ed = new EmailDocument(from, to, subject, body, time);
myWriter.addDocument(ed);
....
Hits hits = mySearcher.search(...);
EmailDocument ed = (EmailDocument) hits.doc(1);
System.out.println(ed.getFrom());
I can package the object/index mapping logic into the EmailDocument class.
peter
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