java 17 support

[just1602]

Hello!

I try to update an application that use Gson to java 17 this morning and I get the following warning and error :

WARNING: Illegal reflective access by com.google.gson.internal.reflect.UnsafeReflectionAccessor (file:/app/libs/gson-2.8.7.jar) to constructor java.lang.StackTraceElement()

java.lang.reflect.InaccessibleObjectException: Unable to make private java.lang.StackTraceElement() accessible: module java.base does not "opens java.lang" to unnamed module 

I was wondering if there was plan to make Gson compatible with java 17 since reflexive call to internal API isn't allowed anymore?

A blog article about the java runtime encapsulation : https://blogs.oracle.com/javamagazine/java-runtime-encapsulation-internals

[Marcono1234]

Gson will only perform perform illegal access when you try to serialize or deserialize a third-party class without having a custom type adapter specified (and for which no built-in adapter exists). In your case it sounds like you are trying to deserialize java.lang.StackTraceElement. Could you please check if that is the case?

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Note that I am not a maintainer of this project.

[just1602]

Thanks! I'll check this out and try to create a type adapter for this class that is use in one of our library. :)

[piegamesde]

Please reopen. There definitely should be a built-in type adapter in GSON for types like Exception and StackTraceElement.

[Marcono1234]

@piegamesde, this issue was specifically about being unable to use reflection for JDK classes. The previous functionality was inherently unreliable because it depended on JDK internals.
If you think Gson should provide built-in adapters for Exception (or even Throwable) and StackTraceElement feel free to create a new feature request issue.

(This is also related to #469)

[Marcono1234]

There is now a feature request for proper support for Throwable: #2352