Hey thanks for all the feedback.
So I got a working solution, bits and pieces of this solution online.
Cedric mentioned it, but basically, I'm having my java code call a clojure
function that (via STM), pushes new event objects to a list in Clojure
(fig.1). And with my Clojure code in place, my Java code looks like the
below (fig.2). And this ensures that the Java callback pushes to an STM
guarded place in memory.
(def event-list (ref ()))
(defn pushEvent [event]
(dosync (alter event-list conj event) ))
(defn -pushEvent [event]
(pushEvent event))
fig.1
eventObject = ... ;
//Load the namespace
RT.var("clojure.core","eval").invoke(RT.var("clojure.core","read-string").invoke("(use
'my.namespace)"));
//Find a function in namespace
IFn fn = (IFn)RT.var("my.namespace","my-function");
//Call that function
Object result = *fn.invoke( eventObject );*
System.out.println(result);
fig.2
Now, this works, but I'm always open to a better idea. In clojure-land, 1)
there's a thread constantly checking for new events on the list and 2)
there will be a thread of execution for each eventID. So I'm trying to come
up with the best data and functional pattern to handle all this. I'm not
sure a plain-jane Clojure list does the trick.
Hmm
Tim
No 6: "I'm not a number. I'M A FREE MAN!!!"
No 2: "HA HA HA HA HAAAAAAA"
-- The Prisoner
On Tue, Apr 9, 2013 at 3:48 PM, Cedric Greevey <[email protected]> wrote:
> On Tue, Apr 9, 2013 at 12:41 PM, Timothy Washington <[email protected]>wrote:
>
>> Hi all,
>>
>> I have a polyglot project, comprising of a little Java and mostly Clojure
>> code. The Java class is a concrete callback for an external library. There
>> will be sub-second firing of that callback, and event map objects will get
>> pushed onto a list.
>>
>
> Now, after the generic advice for sharing state between Java and Clojure,
> in your specific case it sounds like you might have only a single piece of
> state and it *may* be a queue being produced by the Java callback and
> consumed by Clojure.
>
> In the single-piece-of-state-but-not-a-queue case you could use
> java.util.concurrent.AtomicReference around a java.util.List from the Java
> side, or even a Clojure atom (clojure.lang.Atom class).
>
> In the queue case you can do better:
> java.util.concurrent.LinkedBlockingQueue. In the callback class, static
> LinkedBlockingQueue queue = new LinkedBlockingQueue(); and, in the callback
> method, queue.offer(anotherEventMapObject); in the Clojure code, (.poll
> CallbackClass/queue) to fetch an event map in the consumer (it will block,
> as the name implies, if the queue is empty until the producer offers
> another one, so you might want a dedicated thread to do the consuming,
> depending).
>
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