Resolving java.lang.UnsupportedOperationException: PermittedSubclasses Requires by Updating ASM and Related Dependencies

While studying Java virtual threads, the author encountered a java.lang.UnsupportedOperationException: PermittedSubclasses requires error after upgrading the JDK, caused by an outdated ASM library that does not support JDK 9+.

Step 1 – Remove old ASM dependencies: Using the Maven‑helper plugin, search for existing ASM artifacts and exclude them with the excludes syntax.

Step 2 – Add a compatible ASM version: Include ASM 9.2 (or any version that supports the current JDK) in the pom.xml :

<dependency>
    <groupId>org.ow2.asm</groupId>
    <artifactId>asm</artifactId>
    <version>9.2</version>
</dependency>

In many cases this alone resolves the issue because other libraries may already bring the required ASM transitive dependency.

Step 3 – Upgrade related libraries: The JsonPath library used an old ASM version, so updating it to the latest release eliminated further conflicts.

Step 4 – Check Groovy SDK and Maven‑Groovy plugin: An outdated Groovy SDK and Maven‑Groovy compiler plugin also caused failures. The correct configurations are:

<dependency>
    <groupId>org.codehaus.groovy</groupId>
    <artifactId>groovy</artifactId>
    <version>3.0.19</version>
</dependency>

<plugins>
    <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-dependency-plugin</artifactId>
        <version>3.0.1</version>
        ...
    </plugin>
    <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-shade-plugin</artifactId>
        <version>3.2.4</version>
        ...
    </plugin>
</plugins>

Step 5 – Handle Log4j shutdownHook warning: After the JDK upgrade, Log4j prints a warning about the shutdown hook. Adding shutdownHook="disable" to the Log4j2 configuration silences the warning:

<configuration status="WARN" monitorInterval="30" shutdownHook="disable">
    ...
</configuration>

Following these steps resolves the ASM compatibility error and eliminates the additional Log4j warning, allowing the project to run smoothly on the upgraded JDK.