Well there is a remove method in ClassValue,
http://docs.oracle.com/javase/7/docs/api/java/lang/ClassValue.html#remove(java.lang.Class)and
it seems that the cache is implemented in a way that it does not hold
class objects, thus it does not prevent class from GCing (the cached value
is stored in class object itself).
On Thu, Jan 30, 2014 at 3:40 PM, Ambrose Bonnaire-Sergeant <
abonnaireserge...@gmail.com> wrote:
> Is there any way to invalidate this cache?
>
> Thanks,
> Ambrose
>
>
> On Thu, Jan 30, 2014 at 9:35 PM, pron <ron.press...@gmail.com> wrote:
>
>> The bean function is a very useful Java interop feature that provides a
>> read-only view of a Java Bean as a Clojure map.
>> As it stands, the function performs introspection on the bean's class
>> whenever the function is called:
>>
>>
>> (defn bean
>> "Takes a Java object and returns a read-only implementation of the
>>
>>
>> map abstraction based upon its JavaBean properties."
>> {:added "1.0"}
>>
>>
>> [^Object x]
>> (let [c (. x (getClass))
>>
>>
>> pmap (reduce1 (fn [m ^java.beans.PropertyDescriptor pd]
>>
>>
>> (let [name (. pd (getName))
>>
>>
>> method (. pd (getReadMethod))]
>>
>>
>> (if (and method (zero? (alength (. method
>> (getParameterTypes)))))
>>
>>
>> (assoc m (keyword name) (fn []
>> (clojure.lang.Reflector/prepRet (.getPropertyType pd) (. method (invoke x
>> nil)))))
>>
>>
>> m)))
>> {}
>> (seq (.. java.beans.Introspector
>>
>>
>> (getBeanInfo c)
>>
>>
>>
>> (getPropertyDescriptors))))
>> v (fn [k] ((pmap k)))
>>
>>
>> snapshot (fn []
>> (reduce1 (fn [m e]
>>
>>
>> (assoc m (key e) ((val e))))
>>
>>
>> {} (seq pmap)))]
>>
>>
>>
>> (proxy [clojure.lang.APersistentMap]
>> []
>>
>>
>> (containsKey [k] (contains? pmap k))
>>
>>
>> (entryAt [k] (when (contains? pmap k) (new clojure.lang.MapEntry k (v
>> k))))
>>
>>
>> (valAt ([k] (when (contains? pmap k) (v k)))
>>
>>
>> ([k default] (if (contains? pmap k) (v k) default)))
>>
>>
>> (cons [m] (conj (snapshot) m))
>>
>>
>> (count [] (count pmap))
>>
>>
>> (assoc [k v] (assoc (snapshot) k v))
>>
>>
>> (without [k] (dissoc (snapshot) k))
>>
>>
>> (seq [] ((fn thisfn [plseq]
>>
>>
>> (lazy-seq
>> (when-let [pseq (seq plseq)]
>>
>>
>> (cons (new clojure.lang.MapEntry (first pseq) (v (first
>> pseq)))
>>
>>
>> (thisfn (rest pseq)))))) (keys pmap))))))
>>
>>
>>
>>
>>
>> I propose to cache the pmap value for each class using JDK 7's
>> ClassValue<http://docs.oracle.com/javase/7/docs/api/>.
>> Here's a proposed implementation:
>>
>>
>> (def ^:private ^java.lang.ClassValue bean-class-value
>>
>>
>> (proxy [java.lang.ClassValue]
>> []
>> (computeValue [c]
>>
>>
>> (reduce (fn [m ^java.beans.PropertyDescriptor pd]
>>
>>
>> (let [name (. pd (getName))
>>
>>
>> method (. pd (getReadMethod))
>>
>>
>> type (.getPropertyType pd)]
>> (if (and method (zero? (alength (. method
>> (getParameterTypes)))))
>>
>>
>> (assoc m (keyword name) (fn [x]
>> (clojure.lang.Reflector/prepRet type (. method (invoke x nil)))))
>>
>>
>> m)))
>> {}
>> (seq (.. java.beans.Introspector
>>
>>
>> (getBeanInfo c)
>> (getPropertyDescriptors)))))))
>>
>>
>>
>> (defn bean
>> "Takes a Java object and returns a read-only implementation of the
>>
>>
>> map abstraction based upon its JavaBean properties."
>> {:added "1.0"}
>>
>>
>> [^Object x]
>> (let [c (. x (getClass))
>>
>>
>> pmap (.get bean-class-value c)
>>
>>
>> v (fn [k] ((pmap k) x))
>>
>>
>> snapshot (fn []
>> (reduce (fn [m e]
>>
>>
>> (assoc m (key e) ((val e) x)))
>>
>>
>> {} (seq pmap)))]
>> (proxy [clojure.lang.APersistentMap]
>>
>>
>> []
>> (containsKey [k] (contains? pmap k))
>>
>>
>> (entryAt [k] (when (contains? pmap k) (new clojure.lang.MapEntry k (v
>> k))))
>>
>>
>> (valAt ([k] (when (contains? pmap k) (v k)))
>>
>>
>> ([k default] (if (contains? pmap k) (v k) default)))
>>
>>
>> (cons [m] (conj (snapshot) m))
>>
>>
>> (count [] (count pmap))
>> (assoc [k v] (assoc (snapshot) k v))
>>
>>
>> (without [k] (dissoc (snapshot) k))
>>
>>
>> (seq [] ((fn thisfn [plseq]
>>
>>
>> (lazy-seq
>> (when-let [pseq (seq plseq)]
>>
>>
>> (cons (new clojure.lang.MapEntry (first pseq) (v (first
>> pseq)))
>>
>>
>> (thisfn (rest pseq)))))) (keys pmap))))))
>>
>>
>>
>>
>>
>>
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>
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