Usage of strong references on Method/Constructor & WeakHashMap usage
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Key: JEXL-61
URL: https://issues.apache.org/jira/browse/JEXL-61
Project: Commons JEXL
Issue Type: Improvement
Affects Versions: 2.0, 1.1.1
Reporter: Henri Biestro
Fix For: Later
In MethodMap and IntrospectorBase in 2.0, we are using strong references on
Method(s) and Constructor(s).
However, the ClassMap is using a WeakHashMap keyed on class and
IntrospectorBase use SoftRefence on classes to allow the GC to remove them if
the need arise.
I might misunderstand the whole thing but it seems "odd" since the GC can
probaby *not* remove a class for which a strong reference on method or
constructor exists; the getDeclaringClass seems to prevent this from being
possible. The fix would be to use SoftReference on those List<Method> and
Constructor used in the code.
The second - nitpicking - oddity is that a WeakHashMap is not the best fit for
the kind of cache Jexl is using; a "SoftHashMap" should be a better choice; but
the previous fix could prevent the inherent WeakHashMap problem too since
holding those methods/ctors through SoftReference should still make "hard
enough" references to the classes held by the keys for them to be removed.
In any case, the code is this way since its origin and no-one has complained
(yet) about this (obscure feature to me) which documented intent is to "detect
class loader changes"., thus the low priority. My (wild)guess is that anyone
having really encountered this issue probably increased permSpace size for
other reasons.
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