Adding a link() Method to Method

[Alan Bateman]

Jeremy Manson wrote:
> Hi folks,
>
> I found myself in need of a method that determines whether a given
> native method is linked, and links it if it is present.  My use case
> prevents me from calling the method directly and catching an
> UnsatisfiedLinkError, because the method has side effects.
>
> This is not the first time I've needed such a method, so I implemented
> it and dropped it into java.lang.reflect.Method. I thought I would ask
> if it was something that should be added to the platform.  The
> prototype looks like this:
>
>    /**
>     * Attempts to link this method, per Section 5.6 of the Java
>     * Virtual Machine Specification.  Returns {@code true} if this is
>     * a Java method, or if it is a native method and the Java Virtual
>     * Machine succeeds in loading an appropriate native-language
>     * definition of it; returns {@code false} otherwise.
>     *
>     * @return {@code true} if this is a Java method, or if it is a
>     * native method and the Java Virtual Machine succeeds in
>     * loading an appropriate native-language definition of it; returns
>     * {@code false} otherwise.
>     *
>     * @since 1.7
>     */
>    public boolean tryLink();
>
> This is basically useful in any case where you would otherwise catch
> UnsatisfiedLinkError, but can't invoke the method.  For example, if
> you have a binary that lives on the system, but you aren't sure
> whether that shared library provides the implementation you want.
>
> (Another point in the design space would be to have it called link(),
> return void, and throw an UnsatisfiedLinkError if it fails.  It is
> also worth pointing out that the JVMS calls it "binding", not
> "linking", so there is that possibility as well.)
>
> What do you all think?  It seems equally as useful as the ability to
> catch UnsatisfiedLinkError from native method invocation.
>
> Jeremy
>   
In your example, is this a versioning issue with the native library? 
Just wondering if it would make more sense to write a native method that 
returns a version number of some such? One thing to mention is that you 
could encounter libraries that do their own linking with RegisterNatives.

-Alan.