RFE: annotation for resource wrapper methods

[Rob Spoor]

Hi,

When you wrap a resource (InputStream, etc) using a class constructor 
(e.g. new BufferedInputStream(...)), compilers usually don't complain. 
If you do the exact same thing using a utility method, compilers aren't 
that smart anymore. For instance, the following produces a warning that 
the FileInputStream may not be closed, even though the wrap method 
returns a new InputStream that closes the FileInputStream if it's closed 
itself:

     try (InputStream decoded = Base64.getDecoder().wrap(new 
FileInputStream("filename"))) {
         ...
     }

It would be nice if there were some annotation that we could use to mark 
a method as being resource-safe, because they either close the resource, 
or return a wrapper around it. It would be a bit like @SafeVarargs but 
for resources. Methods like wrap would then be annotated with this new 
annotation, and compilers shouldn't complain anymore. The alternative is 
a lot more verbose:

     try (@SuppressWarnings("resource") InputStream decoded = 
Base64.getDecoder().wrap(new FileInputStream(""))) {
         ....
     }


(I don't know if this is the right mailing list, but I couldn't find a 
better one.)


Kind regards,

Rob