gwt-plugin compile-error with JDK-17: Unable to make private final sun.util.calendar.BaseCalendar$Date java.util.Date.getCalendarDate() accessible - gwt

Question

I try to upgrade my large java-application from jdk-11 to jdk-17. On jdk-11 all is ok.
We use the following gwt-plugin (version 1.0.1) to compile:
<plugin>
<groupId>net.ltgt.gwt.maven</groupId>
<artifactId>gwt-maven-plugin</artifactId>
<configuration>
<moduleName>xxxxxxxxxxxxx</moduleName>
<jvmArgs>
<jvmArg>-showversion</jvmArg>
<jvmArg>-Xmx2048M</jvmArg>
</jvmArgs>
</configuration>
<executions>
<execution>
<goals>
<goal>compile</goal>
</goals>
</execution>
</executions>
</plugin>
but the compile complains with:
[INFO] --- gwt-maven-plugin:1.0.1:compile (default-cli) # xxxxxxx ---
[WARNING] openjdk version "17.0.2" 2022-01-18 LTS
[WARNING] OpenJDK Runtime Environment Zulu17.32+13-CA (build 17.0.2+8-LTS)
[WARNING] OpenJDK 64-Bit Server VM Zulu17.32+13-CA (build 17.0.2+8-LTS, mixed mode, sharing)
[INFO] Compiling module xxxxxxxx
...
[INFO] java.lang.reflect.InaccessibleObjectException: Unable to make private final sun.util.calendar.BaseCalendar$Date java.util.Date.getCalendarDate() accessible: module java.base does not "opens java.util" to unnamed module #145f66e3
[INFO] at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:354)
[INFO] at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:297)
[INFO] at java.base/java.lang.reflect.Method.checkCanSetAccessible(Method.java:199)
[INFO] at java.base/java.lang.reflect.Method.setAccessible(Method.java:193)
[INFO] at org.hibernate.validator.util.privilegedactions.SetAccessibility.run(SetAccessibility.java:39)
[INFO] at org.hibernate.validator.util.ReflectionHelper.setAccessibility(ReflectionHelper.java:354)
[INFO] at org.hibernate.validator.metadata.BeanMetaDataImpl.addMethodMetaConstraint(BeanMetaDataImpl.java:474)
[INFO] at org.hibernate.validator.metadata.BeanMetaDataImpl.initMethodConstraints(BeanMetaDataImpl.java:654)
[INFO] at org.hibernate.validator.metadata.BeanMetaDataImpl.initClass(BeanMetaDataImpl.java:546)
[INFO] at org.hibernate.validator.metadata.BeanMetaDataImpl.createMetaData(BeanMetaDataImpl.java:540)
[INFO] at org.hibernate.validator.metadata.BeanMetaDataImpl.<init>(BeanMetaDataImpl.java:209)
[INFO] at org.hibernate.validator.metadata.BeanMetaDataImpl.<init>(BeanMetaDataImpl.java:163)
[INFO] at org.hibernate.validator.engine.ValidatorImpl.getBeanMetaData(ValidatorImpl.java:1211)
[INFO] at org.hibernate.validator.engine.ValidatorImpl.getConstraintsForClass(ValidatorImpl.java:251)
[INFO] at com.google.gwt.validation.rebind.BeanHelperCache.doCreateHelper(BeanHelperCache.java:113)
If I add the add-opens parameter like this:
<plugin>
<groupId>net.ltgt.gwt.maven</groupId>
<artifactId>gwt-maven-plugin</artifactId>
<configuration>
<moduleName>xxxxxxxxxxxxx</moduleName>
<jvmArgs>
<jvmArg>-showversion</jvmArg>
<jvmArg>-Xmx2048M</jvmArg>
<jvmArg>--add-opens java.base/java.util=ALL-UNNAMED</jvmArg>
</jvmArgs>
</configuration>
<executions>
<execution>
<goals>
<goal>compile</goal>
</goals>
</execution>
</executions>
</plugin>
then, I get the following error:
[INFO] --- gwt-maven-plugin:1.0.1:compile (default-cli) # xxxxxx ---
[WARNING] Unrecognized option: --add-opens java.base/java.util=ALL-UNNAMED
[WARNING] Error: Could not create the Java Virtual Machine.
[WARNING] Error: A fatal exception has occurred. Program will exit.
Above the log stated, that I use a jdk-17.
How do I need to set the add-opens parameter ?
Do you see any other workaround?

Answer 1

The comment from Stuart solved my issue. Thanks a lot.
The following configuration worked for me:
<plugin>
<groupId>net.ltgt.gwt.maven</groupId>
<artifactId>gwt-maven-plugin</artifactId>
<configuration>
<moduleName>xxxxxxxx</moduleName>
<jvmArgs>
<jvmArg>-showversion</jvmArg>
<jvmArg>-Xmx2048M</jvmArg>
<jvmArg>--add-opens</jvmArg>
<jvmArg>java.base/java.util=ALL-UNNAMED</jvmArg>
</jvmArgs>
</configuration>
<executions>
<execution>
<goals>
<goal>compile</goal>
</goals>
</execution>
</executions>
</plugin>