Re: trySetAccessible​

[mandy chung]

As described in the javadoc [1], Module::isOpen(String pn) returns true 
if this module has opened a package unconditionally. It returns true 
only if the module declares "opens pn;" unconditionally in 
module-info.java.  Since java.base does not open "java.io" 
unconditionally, so isOpen("java.io”) returns false.

Mandy
[1] 
http://download.java.net/java/jdk9/docs/api/java/lang/Module.html#isOpen-java.lang.String-

On 8/15/17 6:09 PM, Russell Gold wrote:
> I am clearly missing something, here. Using build 180, I have variables:
>
> Method method, Class callingClass.
>
> I evaluate:
>
> callingClass.getModule() -
> 		-> java.lang.Module at 2940 “unnamed module @f973499”
> method.getDeclaringClass()
> 		-> java.lang.Class “class java.io.ObjectInputStream”
> method.getDeclaringClass().getModule()
> 		-> java.lang.Module @2949 “module java.base"
> method.getDeclaringClass().getModule().isOpen("java.io”)
> 		-> false // which I read as saying that package “java.io” in module java.base is NOT open to the unnamed module
>
> but:
>
> method.getDeclaringClass().getModule().isOpen("java.io", callingClass.getModule())
> 		-> true  // which seems to say that it IS open to that particular unnamed module ?!
>
> of course, method.setAccessible(true) gives me the warning.
>
> What am I missing?
>
> Thanks,
> Russ
>
>> On Jul 11, 2017, at 6:11 AM, Alan Bateman <Alan.Bateman at oracle.com> wrote:
>>
>> On 11/07/2017 10:16, Uwe Schindler wrote:
>>> :
>>> Sorry, I mixed up the parameters. So basically the "correct" code to check if something like java.lang.String is open to Groovy would be:
>>>
>>> Module groovyModule = CachedClass.class.getModule(); // org.codehaus.groovy.reflection.CachedClass;
>>> Class clazz = String.class; // to test if open
>>> return clazz.getModule().isOpen(String.class.getPackage().getName(), groovyModule);
>>>
>>> If I do this, it returns "true" for String, Object or any other class. So the behaviour is consistent.
>> Yes, it has to be consistent.
>>
>> As an aside, you can replace getPackage().getName() with getPackageName() - it's more efficient and avoids the NPE when the class is an array or primitive.
>>
>>
>>> I implemented this check as a single MethodHandle to a precompiled method that takes a Class<?> and returns true/false if the Class is open to Groovy's module: https://goo.gl/XvdCQK
>>> By this it's possible to execute this without a Java 9 at compile time. Unfortunately, it doesn't help, because java.base is open to unnamed module
>> Right, although isOpen("java.lang") will return false because the package is not open to all modules.
>>
>>
>>> But now it is impossible for us to check, if something is not open by default.
>> Module::getDescriptor will return the module descriptor for named modules. So in this case, Object.class.getModule().getDescriptor() returns the ModuleDescriptor for java.base so you can inspect the packages and which are exported and/or opened before being changed by runtime. So there is enough in the API to determine which packages have been opened at runtime (either via CLI options or APIs).
>>
>> -Alan