Getting Java Class objects, and JSS

Alan Ruttenberg alanruttenberg at
Wed Jul 8 15:59:17 UTC 2015

There are also specific forms for certain kinds of optimization. An
examples is with-constant-signature

In the following, the method lookup for #"Foo" and #"Bar" are looked up
based on the signature of the arguments for the first call of the function
in the body. Thereafter the methods are called directly. Doesn't work if
you might have different types returned, but in many cases of optimization
one doesn't.

(let ((baz something))
   (with-constant-signature ((foo "Foo") (bar "Bar"))
     (dotimes (i 1000) (foo (bar baz)))))

I haven't looked at dynamic dispatch in recent Java but it is possible that
the implementation might move to that if it performs better.


On Wed, Jul 8, 2015 at 7:42 AM John Pallister <john at> wrote:

> Hi Mark,
> Thanks for pointing out getClass(), I should've thought of that myself...
> And thanks for the JSS information, I'll have a look into that.
> On 8 July 2015 at 08:27, Mark Evenson <evenson at> wrote:
>> > On 07 Jul 2015, at 22:24, John Pallister <john at> wrote:
>> […]
>> > Some of the tutorials have code like:
>> >
>> >   context.addServlet(HelloServlet.class, "/");
>> >
>> > Is it possible to get Class objects for Java classes I've made with
>> JNEW-RUNTIME-CLASS (or indeed for any other Java class)?
>> Since all Java references to non-primitive types descend from
>> java.lang.Object,
>> one may always get a reference to the class object by [calling the
>> “getClass()”
>> method][1].
>> [1]:
>> > I've been using "raw" JCLASS & JMETHOD etc. calls to experience just how
>> > painful that really is, but I'm apprehensive about using JSS and paying
>> the
>> > runtime dynamic dispatch penalty, given that on GAE time is money.
>> Something
>> > more like a SLIME plug-in that looked up & cached classes, methods &
>> fields at
>> > editing time (perhaps also parsing Java expressions) and generated
>> "statically
>> > typed" code would be nice (possibly using code from e.g. JDEE and/or
>> CEDET) -
>> > has anyone else thought about this?
>> I wouldn’t necessarily be afraid of the “penalty" for using JSS, or at
>> least, I
>> might benchmark the difference in performance before shying away from JSS
>> at
>> the outset.
>> JSS [already creates a cache of all classes that on the classpath][2].
>> JSS:JAVA-CLASS-METHOD-NAMES provides a listing of all methods of a class,
>> which
>> is not currently cached, but could be.  Extending this to java fields
>> would be
>> useful.  I would welcome patches to JSS which extends these introspection
>> facilities as the basis for the tooling you wish to build.
>> [2]:
>> [3]:
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