Re: [xsl] [java] transforming a file to itself - buffered?

[Robert Koberg <rob@xxxxxxxxxx>]

Hi and thanks Joerg,

J.Pietschmann wrote:

> Robert Koberg wrote:
>
> > What is the best way to handle transforming a file to itself?
> >
> > Currently I do:
> > File source = new File(servlet_context.getRealPath(_xml));
> > transformer.transform(new StreamSource(source), new 
> > StreamResult(source));
>
>
> Opening a file both for reading and writing at the same
> time is always risky. Either write to a buffer, and write
> the buffer to disk after the transformation has finished,
> or write to a temporary file and rename to the original
> file afterwards.

The reason I want to use java.nio is because there is a locking method. 
It can lock the entire file or parts of the file. I am just 
experimenting... I can open the file and provide the source through nio. 
I would like to be able to write to the part of the document that i have 
specified. Currently I only let one user access a particular file at a time.

> Something like;
>  ByteArrayOutputStream baos=new B...;
>  File source = new File(servlet_context.getRealPath(_xml));
>  transformer.transform(new StreamSource(source), new StreamResult(baos));
>  byte buf[]=baos.toByteArray();
>  new FileOutputStream(source).write(buf);
>
> BTW doing this in a servlet context appears to be
> rather strange...

Why? Am I doing something stupid? I have only had a few concurrent users 
at any one time and there has not been any problems. The user base for 
any 'one' set of files is pretty small (1-10 users).

thanks again,
-Rob



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