Implementing a FileSystemProvider

[Alan Bateman]

Christian Schlichtherle wrote:
>
> Hi Alan,
>
>  
>
> now that I've released TrueZIP 7.1 (http://truezip.java.net), I have 
> finally some time to look into the FileSystemProvider implementation.
>
>  
>
> I wonder if it's OK for a java.nio.file.spi.FileSystemProvider 
> implementation to use the java.io.File* classes or if this might 
> create a recursion? If not OK, which conditions could lead to a 
> recursion then?
>
>  
>
> I recall from our conversations some time ago that federation is not 
> supported in JSE 7. I take from this that File* classes never look up 
> a FileSystemProvider and therefore it should be safe to use File* in a 
> FileSystemProvider implementation. Is this correct?
>
>  
>
> Regards,
>
> Christian
>
It should be okay for providers that implement URI schemes other than 
"file".

However if you want your provider to be the default provider 
(implementing the "file" scheme) then it would be problem if the 
provider used java.io.File (or any of FileInputStream, FileOutputStrea, 
or RandomAccessFile). While it will work now it is unlikely to work in 
the future as these classes should redirect to the default provider when 
it is overridden. There is code in place to detect recursive attempts to 
initialize the default provider but there is nothing except a stack 
overflow that would arise if you invoked a method on java.io.File that 
delegated to the default provider.

-Alan.
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