Could not reconfigure JMX java.lang.LinkageError

Java 8

Maven 3.9,7

I want to validate that a private method was called once.

In my pom.xml:

<dependency> <groupId>org.mockito</groupId> <artifactId>mockito-core</artifactId> <version>3.12.4</version> <scope>test</scope> </dependency> <dependency> <groupId>org.mockito</groupId> <artifactId>mockito-inline</artifactId> <version>3.12.4</version> <scope>test</scope> </dependency> <dependency> <groupId>org.powermock</groupId> <artifactId>powermock-module-junit4</artifactId> <version>2.0.2</version> <scope>test</scope> </dependency> <dependency> <groupId>org.powermock</groupId> <artifactId>powermock-api-mockito2</artifactId> <version>2.0.2</version> <scope>test</scope> </dependency> 

Here's my class:

public class MyClass { @Override public void handle(AttendantRequestEvent event) { String eventId = UUID.randomUUID().toString(); myPrivateMethod(eventId, eventId); } private void myPrivateMethod(String eventId, String eventId2) { System.out.println("myPrivateMethod, eventId = " + eventId + ", eventId2 = " + eventId2); } } 

Here's the unit test:

import static org.assertj.core.api.Assertions.assertThat; import static org.junit.Assert.assertNotNull; import static org.mockito.Answers.RETURNS_DEEP_STUBS; import static org.mockito.ArgumentMatchers.any; import static org.mockito.Mockito.*; import org.junit.Before; import org.junit.Test; import org.junit.runner.RunWith; import org.mockito.*; import org.powermock.api.mockito.PowerMockito; import org.powermock.core.classloader.annotations.PrepareForTest; import org.powermock.modules.junit4.PowerMockRunner; @RunWith(PowerMockRunner.class) @PrepareForTest(MyClass.class) public class MyClassTest { @Test public void shouldCallMyPrivateMethod() throws Exception { try (MockedStatic<UUID> utilities = Mockito.mockStatic(UUID.class)) { AssistanceRequestsHandler assistanceRequestsHandlerMock = PowerMockito.spy(new AssistanceRequestsHandler()); String fixedUuid = "a1b2c3d4-e5f6-7890-1234-567890abcdef"; UUID uuidMock = mock(UUID.class); utilities.when(UUID::randomUUID).thenReturn(uuidMock); when(uuidMock.toString()).thenReturn(fixedUuid); // Act assistanceRequestsHandlerMock.handle(new InfoEvent(any())); // Assert PowerMockito.verifyPrivate(assistanceRequestsHandlerMock, times(1)) .invoke("myPrivateMethod", fixedUuid, fixedUuid); } } } 

And it's working just fine. Here's a result:

myPrivateMethod, eventId = a1b2c3d4-e5f6-7890-1234-567890abcdef, eventId2 = a1b2c3d4-e5f6-7890-1234-567890abcdef 

Nice.

Now, I want to use a logger in my private method, e.g. something like this (in MyClass.java):

private void myPrivateMethod(String eventId, String eventId2) { Logger.info(this, "myPrivateMethod, eventId_1 = {}, eventId_2 {}", eventId, eventId2); } 

And the test was successfully passed, but it raised the next error:

ScriptEngineManager providers.next(): javax.script.ScriptEngineFactory: Provider jdk.nashorn.api.scripting.NashornScriptEngineFactory not a subtype 2025-04-25 12:12:15,086 main ERROR Could not reconfigure JMX java.lang.LinkageError: loader constraint violation: loader (instance of org/powermock/core/classloader/javassist/JavassistMockClassLoader) previously initiated loading for a different type with name "javax/management/MBeanServer" at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClass(ClassLoader.java:757) at org.powermock.core.classloader.javassist.JavassistMockClassLoader.loadUnmockedClass(JavassistMockClassLoader.java:90) at org.powermock.core.classloader.MockClassLoader.loadClassByThisClassLoader(MockClassLoader.java:104) at org.powermock.core.classloader.DeferSupportingClassLoader.loadClass1(DeferSupportingClassLoader.java:147) at org.powermock.core.classloader.DeferSupportingClassLoader.loadClass(DeferSupportingClassLoader.java:98) at java.lang.ClassLoader.loadClass(ClassLoader.java:352) at org.apache.logging.log4j.core.jmx.Server.unregisterAllMatching(Server.java:337)