tomcat 6/7 stream closed error in ring json - works in lein ring server

[Colin Yates]

Hi all,

I have developed a ring/compojure app which receives and servers JSON.  All is well in 'lein ring server' but as soon as I do 'lein ring uberwar' and deploy it to tomcat 6 or 7 it fails.  To be explicit, the app deploys and I can view the static resources, but as soon as I issue a JSON POST I get the following error:

[code]

java.io.IOException: Stream closed

org.apache.catalina.connector.InputBuffer.read(InputBuffer.java:325)

org.apache.catalina.connector.CoyoteInputStream.read(CoyoteInputStream.java:193)

sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:283)

sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:325)

sun.nio.cs.StreamDecoder.read(StreamDecoder.java:177)

java.io.InputStreamReader.read(InputStreamReader.java:184)

java.io.BufferedReader.fill(BufferedReader.java:154)

java.io.BufferedReader.read(BufferedReader.java:175)

clojure.core$slurp.doInvoke(core.clj:6279)

clojure.lang.RestFn.invoke(RestFn.java:410)

ring.middleware.json$read_json.doInvoke(json.clj:12)

clojure.lang.RestFn.invoke(RestFn.java:423)

ring.middleware.json$wrap_json_body$fn__1031.invoke(json.clj:19)

ring.middleware.json$wrap_json_params$fn__1035.invoke(json.clj:31)

compojure.core$routing$fn__362.invoke(core.clj:107)

clojure.core$some.invoke(core.clj:2443)

compojure.core$routing.doInvoke(core.clj:107)

clojure.lang.RestFn.applyTo(RestFn.java:139)

clojure.core$apply.invoke(core.clj:619)

compojure.core$routes$fn__366.invoke(core.clj:112)

health.servlet$_service$fn__1016.invoke(servlet.clj:1)

ring.util.servlet$make_service_method$fn__50.invoke(servlet.clj:126)

health.servlet$_service.invoke(servlet.clj:1)

health.servlet.service(Unknown Source)

[/code]

Any help?

[Colin Yates]

Apologies - I just realised a Compojure group existed.  I have posted in there (https://groups.google.com/forum/#!topic/compojure/_jut36dXmCM) as well.

[James Reeves]

Hi Colin,

One of the compromises Ring makes for efficiency is that the body of a request is an InputStream, rather than a static string or byte array pre-loaded into memory. Because it's a stream, it can potentially be consumed by previous middleware.

For some reason you have both wrap-json-body and wrap-json-params in your stacktrace:

    ring.middleware.json$wrap_json_body$fn__1031.invoke(json.clj:19)

  ring.middleware.json$wrap_json_params$fn__1035.invoke(json.clj:31)

Both middleware read from the body InputStream, so one of them is going to fail when you try and read the body twice.

- James

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[Colin Yates]

Hi James,

Not sure why I did that double wrapping..

However, wouldn't that also fail in Jetty?

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[James Reeves]

It would. I'm not sure why one fails and the other does not, unless the request object passed through Tomcat is different somehow, or unless you accidentally sent two different HTTP requests when testing.

Regardless, the error message you've received is pretty clear - the JSON stream is consumed by the first JSON middleware before the second can get to up.

- James

[Colin Yates]

(is this is the longest delay in replying ever? :))

You are right - I mistakenly thought that json-wrap-params only exposed the request params as oppose to exposing the JSONified body in the params; I thought json-wrap-body and json-wrap-params were complimentary.

Now I have read the docs (https://github.com/ring-clojure/ring-json) it is clear that only one is required.

Problem solved - chose one or the other.