Missing Class Informations in heapdumps?

[Bernd]

Hello,

while researching on the following StackOverflow Question (dealing with
minimum footprint on startup) I noticed that the jmap generated heapdump
does not contain all class instances and the ones which are contained do
not list most of the fields of a class.

https://stackoverflow.com/a/44397441/13189

The original question was, why a hello world java class loads so many
classes and especially has so many (115) java.lang.ref.Field instances in
the (jmap -histo) histogram.

To explain this I was expecting to simply query the instances in MAT,
however the Field instances do not show up as reachable and can therefore
not be queries (I think those are cached Field accessors for some system
classes, but I cannot see that in the dump file).

Both Eclipse MAT and jvisualvm Profiler do not show them (and do only show
a small number of class instances and now fields for them).

Is this a known limitation that not all class instances and their fields
are present in the dump or is this more a problem of the tools displaying
the dump? Is this restricted to classes from the system classloader (as I
do not recall having seen that problem in application classes).

Bernd
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