Unable to run my project on Java 16

[Betalord]

Hi,
I just ported my project from older computer to a new one where I have JDK 16 installed, and my app crashes:

com.thoughtworks.xstream.converters.ConversionException: No converter available
---- Debugging information ----
message             : No converter available
type                : java.util.RegularEnumSet
converter           : com.thoughtworks.xstream.converters.enums.EnumSetConverter
message[1]          : Could not initialize class com.thoughtworks.xstream.converters.enums.EnumSetConverter$Reflections
converter[1]        : com.thoughtworks.xstream.converters.reflection.SerializableConverter
message[2]          : Unable to make private void java.util.EnumSet.readObject(java.io.ObjectInputStream) throws java.io.InvalidObjectException accessible: module java.base does not "opens java.util" to unnamed module @6aceb1a5
converter[2]        : com.thoughtworks.xstream.converters.reflection.ReflectionConverter
message[3]          : Unable to make field private static final long java.util.EnumSet.serialVersionUID accessible: module java.base does not "opens java.util" to unnamed module @6aceb1a5
class               : com.betalord.sgx.core.Map
required-type       : com.betalord.sgx.core.Map
converter-type      : com.betalord.sgx.xstreamconverters.MapConverter
path                : /map/supportedPlayers
line number         : 6
version             : 1.4.13
-------------------------------

Any idea why? Was working well with some much older JDK on the other computer.

[joehni]

You have to start the JVM of Java 16 with Option
--illegal-access=permit

[Betalord]

Could you elaborate on this solution a bit? What side effects does it have, why is it needed?

When using it, my Java says:
Java HotSpot(TM) 64-Bit Server VM warning: Option --illegal-access is deprecated and will be removed in a future release.
And a few lines later:
WARNING: All illegal access operations will be denied in a future release

[joehni]

XStream mimics Java serialization, which does a lot of stuff that is not possible with public API. Java 16 changed the preference for the --illegal-access option to allow this access.

[d98ama]

Are there any ways around this? It seems like this option is removed in Java 17:

OpenJDK 64-Bit Server VM warning: Ignoring option --illegal-access=permit; support was removed in 17.0

[Betalord]

I managed to resolve it by passing these parameters:
java --illegal-access=permit --add-opens java.base/java.lang=ALL-UNNAMED --add-opens java.base/java.io=ALL-UNNAMED --add-opens java.base/java.util=ALL-UNNAMED --add-opens java.base/java.util.concurrent=ALL-UNNAMED
which I found in another thread. However, this is a workaround, not a solution.