Lookup.defineClass

[Russell Gold]

Upon further testing, this turns out to be less capable than the “Unsafe” version - in particular, I cannot create a test stub in a closed package. The problem is that unit tests often need to do a number of things like this that make no sense in a production environment. 

The problem has to do with creating test stubs to take the place of JDK objects. In many cases, this requires access to package-protected classes or fields, as the JDK doesn’t provide clean interfaces for a lot of its functionality. In the past, we could do this by defining a subclass in the same package as the JDK class we needed to stub. That no longer works without command-line switches. Related to this, unit tests must often create stub classes specifically in thread context class loaders - but those classes are frequently not in the same package as the test code. This new feature doesn’t support that at all, and I don’t even see a way to use a command line switch to enable it.

- Russ

> On Mar 14, 2017, at 4:47 PM, Alan Bateman <Alan.Bateman at oracle.com> wrote:
> 
> On 14/03/2017 17:37, Russell Gold wrote:
>> Hi Alan,
>> 
>> I am trying this in SimpleStub, and it seems to work for my current test cases if I do this:
>>> MethodHandles.Lookup in = MethodHandles.privateLookupIn( baseClass, MethodHandles.lookup() ).dropLookupMode( MethodHandles.Lookup.PRIVATE );
>>> return in.defineClass(classBytes);
>> 
>> My tests create stubs from public, package-private and protected classes. Is that what you are expecting? It seems a bit overly complex. 
> You get a full-power lookup on the "baseClass", passing your own lookup that proves you have access. Then you drop private access as it's not supported by defineClass at this time. So it looks right.
> 
> 
>> 
>> In gmbal, I see that this may not suffice, as the current interfaces provide no way to supply a class to use as a base. Figuring out how those interfaces are being used might change my answer.
>> 
> Could you add an overloaded register method to ManagedObjectManager to take the Lookup?
> 
> -Alan