Simple interface for objects that are sources for an InputStream.
This is the base interface for Spring's more extensive Resource interface.
For single-use streams, InputStreamResource can be used for any
given InputStream. Spring's ByteArrayResource or any
file-based Resource implementation can be used as a concrete
instance, allowing one to read the underlying content stream multiple times.
This makes this interface useful as an abstract content source for mail
attachments, for example.
Return an InputStream for the content of an underlying resource.
It is expected that each call creates a fresh stream.
This requirement is particularly important when you consider an API such
as JavaMail, which needs to be able to read the stream multiple times when
creating mail attachments. For such a use case, it is required
that each getInputStream() call returns a fresh stream.
the input stream for the underlying resource (must not be null)
java.io.FileNotFoundException - if the underlying resource doesn't exist
java.io.IOException - if the content stream could not be opened