Re: module java.base does not "opens java.lang" to unnamed module

How to solve InaccessibleObjectException ("Unable to make {member} accessible: module {A} does not 'opens {package}' to {B}") on Java 9?

touches on the issue:

Using --add-opens should be considered a workaround.

The right thing is for libraries performing illegal access to fix their issues.

https://www.reddit.com/r/java/comments/p9ymhb/what_exactly_is_the_reason_for_denying_reflection

reflection  removes encapsulation: makes every element in a code unit part of its API

Strong encapsulation aids in maintainability and security.

https://blogs.oracle.com/javamagazine/post/a-peek-into-java-17-continuing-the-drive-to-encapsulate-the-java-runtime-internals

The result is a user class that is tightly coupled to the internal implementation of the JDK.

If enough developers abuse this openness, this leads to a situation in which it is difficult or impossible 

to make changes to the internals, because to do so would break deployed libraries and applications.

This is one of the problems that modules were invented to solve.

I have found:

On app engine there's no need for --add-opens java.base/java.lang=ALL-UNNAMED, only on local jetty.

This java fix for LinkedHashMap reflection failure is probably more worrying:

...

Field field = LinkedHashMap_CustomFieldSerializer.class.getDeclaredField("reflectionHasFailed");

field.setAccessible(true);

...

On Saturday 22 June 2024 at 02:53:52 BST, Craig Mitchell <mail@craig-mitchell.com> wrote:

This is because, from Java 9, access to the Java classes has been restricted.  More info:  https://stackoverflow.com/questions/41265266/how-to-solve-inaccessibleobjectexception-unable-to-make-member-accessible-m

In the case of GWT, if you want exceptions passed back via RPC, GWT needs access to the java.lang classes to serialise them to contain all the Java class details.

So, you need to add:  --add-opens java.base/java.lang=ALL-UNNAMED  when running.

I didn't know it was not recommended.  Why is it bad to do?

On Saturday 22 June 2024 at 3:34:59 am UTC+10 Tim Macpherson wrote:

It happens with the latest tbroyer archetype, just change the server method so it always throws 

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On Fri, Jun 21, 2024 at 4:20 PM, Colin Alworth

<co...@colinalworth.com> wrote:

Can you share a little more detail, like the full error message with stack trace, and the GWT version you're using? Some improvements were made in this area for GWT 2.11, and some messages of this kind are merely warnings, indicating that reflection was attempted and some fallback can usually be used instead.

On Friday, June 21, 2024 at 8:45:59 AM UTC-5 tim_mac...@yahoo.co.uk wrote:

SInce upgrading to Java 11,  throwing a new IllegalArgumentException in an RPC server-side implementation gives  InaccessibleObjectException. It can be stopped by using a VM argument --add-opens, but apparently this is not recommended.
Can anyone  clarify ?

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