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


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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