Two questions regarding implementing ModuleFinder

[Alan Bateman]

On 28/07/2016 16:59, Andrew Dinn wrote:

> :
>
> The part I am dubious about here is the URI, in particular the need to
> provide a scheme (supplied as the String "byteman"). I passed that
> because I get an error if I simply pass null for the scheme (it
> complains that this is not an absolute URI). I can see that the module
> should have a name but why does it need to be absolute? Indeed, why is
> it needed at all? The various javadocs eventually lead to a suggestion
> that the URI may be used by a security manager. If this is really what
> it is for then do I need to worry about having invented scheme 'byteman'
> out of thin air? WIl the security code ever try to convert it to a URL?
The IllegalArgumentException "URI is not absolute" is a bug, it arises 
when converting the URI to a URL, we'll get that fixed.

But to your question then the module location is used as the CodeSource:

      * <p> This URI, when present, is used as the {@linkplain
      * java.security.CodeSource#getLocation location} value of a {@link
      * java.security.CodeSource CodeSource} so that a module's classes 
can be
      * granted specific permissions when loaded by a {@link
      * java.security.SecureClassLoader SecureClassLoader}.

and so interesting when running with a security manager and granting the 
module permissions.

>
> I am required to implement find as it has no default. I also need to
> implement read so I can redirect to the agent to provide the class
> format byte[]. However, it appears that find is only needed so it can be
> called from the default method open and that open is only there to be
> called from the default method read. Is there any possibility that
> something else might call find?
>
The main user of ModuleReader is class loaders that load 
classes/resources from the modules. ClassLoaders need to implement 
methods such as findResource and findResources will attempt to return a 
URL to resources in modules defined to the ClassLoader. You should see 
your find method invoked for these cases.

-Alan