IllegalAccessError when test accesses classes outside of current module (Gradle)

[kevinross]

Describe the bug

Using a package-private constructor in a class in the main source set that extends a class in a different (gradle) subproject, from the test source set causes an IllegalAccessError due to differing classloaders. Reproducer attached.

Expected behavior

AlternateImpl should be able to be instantiated according to the language spec, and indeed it can be with quarkus < 3.22.

Actual behavior

The below stacktrace results from executing ./gradlew :tests:test

class com.example.AlternateImpl tried to access method 'void com.example.SomeImpl.<init>()' (com.example.AlternateImpl is in unnamed module of loader io.quarkus.bootstrap.classloading.QuarkusClassLoader @363c32cc; com.example.SomeImpl is in unnamed module of loader io.quarkus.bootstrap.classloading.QuarkusClassLoader @4c4d27c8)
java.lang.IllegalAccessError: class com.example.AlternateImpl tried to access method 'void com.example.SomeImpl.<init>()' (com.example.AlternateImpl is in unnamed module of loader io.quarkus.bootstrap.classloading.QuarkusClassLoader @363c32cc; com.example.SomeImpl is in unnamed module of loader io.quarkus.bootstrap.classloading.QuarkusClassLoader @4c4d27c8)
	at com.example.AlternateImpl.<init>(AlternateImpl.java:5)
	at com.test.UnitTestingTest.testImpl(UnitTestingTest.java:11)
	at java.base/java.lang.reflect.Method.invoke(Method.java:580)
	at io.quarkus.test.junit.QuarkusTestExtension.runExtensionMethod(QuarkusTestExtension.java:1047)
	at io.quarkus.test.junit.QuarkusTestExtension.interceptTestMethod(QuarkusTestExtension.java:894)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)

How to Reproduce?

issue47646repro.tar.gz

Output of uname -a or ver

Darwin CAOT-KEVINR-M2 24.4.0 Darwin Kernel Version 24.4.0: Wed Mar 19 21:17:25 PDT 2025; root:xnu-11417.101.15~1/RELEASE_ARM64_T6020 arm64

Output of java -version

openjdk version "21" 2023-09-19 OpenJDK Runtime Environment GraalVM CE 21+35.1 (build 21+35-jvmci-23.1-b15) OpenJDK 64-Bit Server VM GraalVM CE 21+35.1 (build 21+35-jvmci-23.1-b15, mixed mode, sharing)

Quarkus version or git rev

3.22.1

Build tool (ie. output of mvnw --version or gradlew --version)

------------------------------------------------------------ Gradle 8.14 ------------------------------------------------------------ Build time: 2025-04-25 09:29:08 UTC Revision: 34c560e3be961658a6fbcd7170ec2443a228b109 Kotlin: 2.0.21 Groovy: 3.0.24 Ant: Apache Ant(TM) version 1.10.15 compiled on August 25 2024 Launcher JVM: 21 (GraalVM Community 21+35-jvmci-23.1-b15) Daemon JVM: /Users/$USER/.sdkman/candidates/java/21-graalce (no JDK specified, using current Java home) OS: Mac OS X 15.4 aarch64

Additional information

No response

[quarkus-bot]

/cc @geoand (kotlin)

[kevinross]

(the issue template mangled the formatting of the version outputs)

[geoand]

cc @holly-cummins

[celcius112]

I'm having the same issue as the one described by @kevinross. In my case I have a @QuarkusTest calling the controller GreetingResource, the later being a package-private class found in another module.

In module A:

@QuarkusTest
// the issue appears no matter if this annotation is present
@TestHTTPEndpoint(GreetingResource.class)
class GreetingResourceTest {
	@Test
	void testHelloEndpoint() {...}
}

In module B:

@Path("/hello")
class GreetingResource {

    @GET
    public String hello() {...}
}

The above code will fail with a similar error:

2025-05-05 13:12:39,360 ERROR [io.qua.ver.htt.run.QuarkusErrorHandler] (executor-thread-1) HTTP Request to /hello failed, error id: d1aab7de-f82a-43ac-bd36-d7719092e410-1: java.lang.IllegalAccessError: failed to access class org.acme.GreetingResource from class org.acme.GreetingResource$quarkusrestinvoker$hello_df324e1539083188359af68039a7afafb7b77cdb (org.acme.GreetingResource is in unnamed module of loader io.quarkus.bootstrap.classloading.QuarkusClassLoader @553f1d75; org.acme.GreetingResource$quarkusrestinvoker$hello_df324e1539083188359af68039a7afafb7b77cdb is in unnamed module of loader io.quarkus.bootstrap.classloading.QuarkusClassLoader @479ac2cb)
	at org.acme.GreetingResource$quarkusrestinvoker$hello_df324e1539083188359af68039a7afafb7b77cdb.invoke(Unknown Source)
	at org.jboss.resteasy.reactive.server.handlers.InvocationHandler.handle(InvocationHandler.java:29)
	at io.quarkus.resteasy.reactive.server.runtime.QuarkusResteasyReactiveRequestContext.invokeHandler(QuarkusResteasyReactiveRequestContext.java:141)
	at org.jboss.resteasy.reactive.common.core.AbstractResteasyReactiveContext.run(AbstractResteasyReactiveContext.java:147)
	at io.quarkus.vertx.core.runtime.VertxCoreRecorder$15.runWith(VertxCoreRecorder.java:637)
	at org.jboss.threads.EnhancedQueueExecutor$Task.doRunWith(EnhancedQueueExecutor.java:2675)
	at org.jboss.threads.EnhancedQueueExecutor$Task.run(EnhancedQueueExecutor.java:2654)
	at org.jboss.threads.EnhancedQueueExecutor.runThreadBody(EnhancedQueueExecutor.java:1627)
	at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.run(EnhancedQueueExecutor.java:1594)
	at org.jboss.threads.DelegatingRunnable.run(DelegatingRunnable.java:11)
	at org.jboss.threads.ThreadLocalResettingRunnable.run(ThreadLocalResettingRunnable.java:11)
	at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
	at java.base/java.lang.Thread.run(Thread.java:1583)

Making GreetingResource public resolves the issue.

A reproducer can be found here:
classloader-issue.zip

[kevinross]

indeed, making them public resolves the problem, but it does break encapsulation

[gsmet]

FWIW, this is only tangentially related to @holly-cummins 's work. I'm on it.

[gsmet]

Oh, let me correct that: the initial issue reported by @kevinross seems related to @holly-cummins 's work and it's probably best if Holly has a look at it.

The issue reported by @celcius112 while relatively similar is completely different and that's what I'm working on.