[zeromq-dev] Java binding

gonzalo diethelm gdiethelm at dcv.cl
Mon Feb 22 15:50:26 CET 2010

> > I don't know if the fact that you can call through JNI a private
> > member function from member functions in another class within the
> > package, is documented to always work in Java, but it SEEMS we could
> > declare these functions private.
> Little digging on the web got me this:
> http://java.sun.com/docs/books/tutorial/java/javaOO/accesscontrol.html
> As far as I understand the text, private member shouldn't be
> from another class in the package. The fact that it works with JNI may
> be just an artifact and we shouldn't use it IMO.

And I found this gem, at sun.com. It seems we can go ahead, declare
these two methods private and enjoy ourselves...


10.9 Violating Access Control Rules

The JNI does not enforce class, field, and method access control
restrictions that can be expressed at the Java programming language
level through the use of modifiers such as private and final. It is
possible to write native code to access or modify fields of an object
even though doing so at the Java programming language level would lead
to an IllegalAccessException. JNI's permissiveness was a conscious
design decision, given that native code can access and modify any memory
location in the heap anyway.

Native code that bypasses source-language-level access checks may have
undesirable effects on program execution. For example, an inconsistency
may be created if a native method modifies a final field after a
just-in-time (JIT) compiler has inlined accesses to the field.
Similarly, native methods should not modify immutable objects such as
fields in instances of java.lang.String or java.lang.Integer. Doing so
may lead to breakage of invariants in the Java platform implementation.

Gonzalo Diethelm

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