Re: is package a namespace?

Joshua Cranmer <Pidgeot18@verizon.invalid>
Thu, 24 Jul 2008 14:00:03 GMT
puzzlecracker wrote:

Is it possible to have the same package extend over different
hierarchical file-system trees --still retain the same structure and
name -- and then place them into the same jar file, and they both can
access each other's package private members?

Under the system classloader, a Java package is strictly limited to one
folder hierarchy. If you use your own classloaders... anything goes.
Except for the interaction between classloaders.

Is it like in C++ that packages can be wired together, thus a
malicious code can be introduce that can tinker with internals of some
api... or Java worked around this problem?

If you don't use your own classloader, the only ways malicious code can
get into the internals is:

a. It asks for, and receives, permission to override security checks on
the classloader.
b. It modifies the jar file before startup.

I have actually used b before (inserting a modified version of
java.lang.Class into the bootstrap path), as well as a.

Beware of bugs in the above code; I have only proved it correct, not
tried it. -- Donald E. Knuth

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