You can't really do this in a single thread without risking blocking.
But with another thread, it's fairly simple. For example, I do this in
my gzip-middleware, copying an InputStream through a pipe with GZIP
wrapping:
https://github.com/amalloy/ring-gzip-middleware/blob/master/src/ring/middleware/gzip.clj#L10
I'm turning an input stream into another input stream, but you can do
something similar. It's a bit weird, because you're really *not*
attempting to convert an outputstream to an inputstream in your
example. You're calling a function that writes to stdout and returns
nil, and hoping that somehow a stream gets created. Really using with-
out-str is a reasonable approach here; just create a StringReader from
the resulting string.
But if you need asynchronicity, you can probably do something like
(let [pipe-in (PipedInputStream.)
pipe-out (PipedOutputStream. pipe-in)]
(future ; new thread to prevent blocking deadlock
(binding [*out* (PrintWriter. pipe-out)]
(ofn var)))
pipe-in)
This lets ofn run in another thread, writing its output to *out*,
which passes through the pipe and becomes an input stream for ring to
use.
On Dec 15, 1:01 pm, Trevor <[email protected]> wrote:
> I have created an output stream, which appears to work fine, however
> I get an error when trying to convert the output stream into an input
> stream for use in ring:
>
> ('use [clojure.java.io :only [input-stream]])
>
> => (with-out-str (ofn var))
> "it works!"
>
> Now when I use ring:
> {:body (input-stream (ofn var))}
>
> java.lang.IllegalArgumentException: No implementation of method: :make-
> input-stream of protocol: #'clojure.java.io/IOFactory found for class:
> nil
>
> Is there something special I need to do to convert output stream into
> an input stream ?
>
> Thanks,
> Trevor
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