Review Request JDK-8200559: Java agents doing instrumentation need a means to define auxiliary classes

[Alan Bateman]

On 16/04/2018 08:11, Rafael Winterhalter wrote:
> :
>
> I also think it is essential to being able to inject a class into a 
> non-opened package. Otherwise one could use a method handle. When 
> instrumenting classes one already has full privilege for all packages 
> as an agent can open modules. If one opens packages to define a class, 
> this would however open the package to the agent's module which is 
> typically the unnamed module. As this cannot be undone, such a 
> requirement might therefore be counter-productive to its intend.
>
It's important to separate the usages.

The Instrumentation object is for tool agents that are doing load time 
or dynamic instrumentation. Agents have full power to do anything and 
the accessibility of the classes that they instrument does not matter. 
With the proposed API, the agent can define classes in the same runtime 
package as the class being loaded or transformed, it does not matter if 
that the package is open or not.

Libraries doing code injection is different of course. There is no 
Instrumentation object in the picture for this scenario. Instead 
libraries must be called with a Lookup that has the appropriate access - 
that should be the only way that they can inject into runtime packages 
that aren't open.

-Alan