On Fri, Jan 21, 2011 at 4:27 AM, weltermann17 <[email protected]>wrote:
> [...] As stated elsewhere in this forum a basic solution could be to always
> call exhaust and release on a representation after using it (samples in
> Scala):
>
> val representation = response.getEntity
> if (null != representation) {
> try {
> // do something with it
> } finally {
> representation.exhaust
> representation.release
> }
> }
>
> To not clutter our code with this we adopted the "Disposable Pattern"
> for Scala:
> [...]
> This allows cleaner code (many details omitted):
> [...]
> With "using" and "disposable" the compiler ensures that in either
> case (success or failure) the representation is exhausted and released. In
> case of failure the exception is handled elsewhere.
>
> Now this is Scala and doesn't help much in a pure Java environment. I
> think it would be great if this were made part of Restlet, but I'm sure
> it wouldn't be easy.
>
I'm still waiting to hear from Jerome or Thierry about whether explicitly
exhausting and releasing every representation is even a good idea, but doing
it in Java isn't hard to do nicely:
JsonNode data = consume(clientRes.get(MediaType.APPLICATION_JSON),
new ReaderRepresentationConsumer<JsonNode>() {
public JsonNode consume(Reader reader) throws Exception {
return getObjectMapper() // using Jackson, but same idea
.readTree(reader)
.get("response")
.get("data");
}
});
where you've defined the following in a utility package for general use:
public interface RepresentationConsumer<T> {
T consume(Representation rep) throws Exception;
}
public abstract class ReaderRepresentationConsumer<T>
implements RepresentationConsumer<T> {
public final T consume(Representation rep) throws Exception {
return consume(new InputStreamReader(rep.getStream()));
}
public abstract T consume(Reader reader) throws Exception;
}
public static <T>
T consume(Representation rep,
RepresentationConsumer<T> consumer)
throws Exception {
try {
return consumer.consume(rep);
} finally {
rep.exhaust();
rep.release();
}
}
This could be tweaked to handle finer-grained exceptions.
And don't forget the try-with-resources language enhancement coming as part
of JSR 334:
try (CloseableRepresentation rep = clientRes.get()) {
// do something with rep
} // automatically calls rep.close(), which could call exhaust, release.
--tim
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