title: PowerMock LinkageError: MockClassLoader javax/management/MBeanServer
body: <p>I'm seeing the following PowerMock/EasyMock error with the following JARS:</p>
  
  <p><strong>Jars</strong></p>
  
  <ul>
  <li>activemq-all-5.9.0.jar</li>
  <li>com.ibm.mq.headers-7.0.1.5.jar</li>
  <li>com.ibm.mq.jmqi-7.5.0.0.jar</li>
  <li>com.ibm.mqjms-7.5.0.0.jar</li>
  <li>javassist-3.9.0.GA.jar</li>
  <li>junit-4.10.jar</li>
  <li>powermock-easymock-1.5.1-full.jar</li>
  <li>com.ibm.mq-7.0.1.5.jar</li>
  <li>easymock-3.2.jar</li>
  <li>objenesis-2.1.jar</li>
  <li>cglib-nodep-2.2.jar</li>
  <li>easymockclassextension-2.4.jar</li>
  <li>com.ibm.disthub2-1.jar</li>
  </ul>
  
  <p><strong>Runtime Error:</strong></p>
  
  <pre><code>java.lang.NoClassDefFoundError: com.ibm.mq.jms.MQQueueConnectionFactory$$EnhancerByCGLIB$$7cb492ab (initialization failure)
      at java.lang.J9VMInternals.initialize(J9VMInternals.java:140)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:60)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37)
      at java.lang.reflect.Method.invoke(Method.java:611)
      at net.sf.cglib.proxy.Enhancer.setCallbacksHelper(Enhancer.java:619)
      at net.sf.cglib.proxy.Enhancer.setThreadCallbacks(Enhancer.java:612)
      at net.sf.cglib.proxy.Enhancer.registerCallbacks(Enhancer.java:581)
      at org.easymock.internal.ClassProxyFactory.createProxy(ClassProxyFactory.java:251)
      at org.easymock.internal.MocksControl.createMock(MocksControl.java:114)
      at org.easymock.internal.MocksControl.createMock(MocksControl.java:88)
      at org.easymock.internal.MocksControl.createMock(MocksControl.java:79)
      at org.powermock.api.easymock.PowerMock.doCreateMock(PowerMock.java:2212)
      at org.powermock.api.easymock.PowerMock.doMock(PowerMock.java:2163)
      at org.powermock.api.easymock.PowerMock.createNiceMock(PowerMock.java:187)
      at QueueServiceTest.testSendMessage(QueueServiceTest.java:30)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:60)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37)
      at java.lang.reflect.Method.invoke(Method.java:611)
      at org.junit.internal.runners.TestMethod.invoke(TestMethod.java:66)
      at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.runTestMethod(PowerMockJUnit44RunnerDelegateImpl.java:310)
      at org.junit.internal.runners.MethodRoadie$2.run(MethodRoadie.java:86)
      at org.junit.internal.runners.MethodRoadie.runBeforesThenTestThenAfters(MethodRoadie.java:94)
      at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.executeTest(PowerMockJUnit44RunnerDelegateImpl.java:294)
      at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.executeTestInSuper(PowerMockJUnit47RunnerDelegateImpl.java:127)
      at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.executeTest(PowerMockJUnit47RunnerDelegateImpl.java:82)
      at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.runBeforesThenTestThenAfters(PowerMockJUnit44RunnerDelegateImpl.java:282)
      at org.junit.internal.runners.MethodRoadie.runTest(MethodRoadie.java:84)
      at org.junit.internal.runners.MethodRoadie.run(MethodRoadie.java:49)
      at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.invokeTestMethod(PowerMockJUnit44RunnerDelegateImpl.java:207)
      at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.runMethods(PowerMockJUnit44RunnerDelegateImpl.java:146)
      at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$1.run(PowerMockJUnit44RunnerDelegateImpl.java:120)
      at org.junit.internal.runners.ClassRoadie.runUnprotected(ClassRoadie.java:34)
      at org.junit.internal.runners.ClassRoadie.runProtected(ClassRoadie.java:44)
      at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.run(PowerMockJUnit44RunnerDelegateImpl.java:118)
      at org.powermock.modules.junit4.common.internal.impl.JUnit4TestSuiteChunkerImpl.run(JUnit4TestSuiteChunkerImpl.java:101)
      at org.powermock.modules.junit4.common.internal.impl.AbstractCommonPowerMockRunner.run(AbstractCommonPowerMockRunner.java:53)
      at org.powermock.modules.junit4.PowerMockRunner.run(PowerMockRunner.java:53)
      at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:49)
      at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
  Caused by: java.lang.LinkageError: loading constraint violation: loader "org/powermock/core/classloader/MockClassLoader@4b564b56" previously initiated loading for a different type with name "javax/management/MBeanServer" defined by loader "com/ibm/oti/vm/BootstrapClassLoader@17e717e7"
      at java.lang.ClassLoader.defineClass(ClassLoader.java:275)
      at java.lang.ClassLoader.defineClass(ClassLoader.java:212)
      at org.powermock.core.classloader.MockClassLoader.loadUnmockedClass(MockClassLoader.java:201)
      at org.powermock.core.classloader.MockClassLoader.loadModifiedClass(MockClassLoader.java:149)
      at org.powermock.core.classloader.DeferSupportingClassLoader.loadClass(DeferSupportingClassLoader.java:67)
      at java.lang.ClassLoader.loadClass(ClassLoader.java:626)
      at com.ibm.msg.client.commonservices.monitor.MonitorAgent.registerMBean(MonitorAgent.java:176)
      at com.ibm.msg.client.commonservices.propertystore.PropertyStore.intializePropertyStoreControl(PropertyStore.java:751)
      at com.ibm.msg.client.commonservices.propertystore.PropertyStore.initialize(PropertyStore.java:515)
      at com.ibm.msg.client.commonservices.CommonServices.&lt;clinit&gt;(CommonServices.java:119)
      at java.lang.J9VMInternals.initializeImpl(Native Method)
      at java.lang.J9VMInternals.initialize(J9VMInternals.java:200)
      at com.ibm.msg.client.commonservices.propertystore.PropertyStore.initialize(PropertyStore.java:512)
      at com.ibm.msg.client.commonservices.propertystore.PropertyStore.&lt;clinit&gt;(PropertyStore.java:235)
      at java.lang.J9VMInternals.initializeImpl(Native Method)
      at java.lang.J9VMInternals.initialize(J9VMInternals.java:200)
      at com.ibm.msg.client.commonservices.trace.Trace.&lt;clinit&gt;(Trace.java:469)
      at java.lang.J9VMInternals.initializeImpl(Native Method)
      at java.lang.J9VMInternals.initialize(J9VMInternals.java:200)
      at java.lang.Class.forNameImpl(Native Method)
      at java.lang.Class.forName(Class.java:139)
      at javassist.runtime.Desc.getClassObject(Desc.java:43)
      at javassist.runtime.Desc.getClazz(Desc.java:52)
      at com.ibm.msg.client.jms.internal.JmsReadablePropertyContextImpl.&lt;clinit&gt;(JmsReadablePropertyContextImpl.java:49)
      at java.lang.J9VMInternals.initializeImpl(Native Method)
      at java.lang.J9VMInternals.initialize(J9VMInternals.java:200)
      at java.lang.J9VMInternals.initialize(J9VMInternals.java:167)
      at java.lang.J9VMInternals.initialize(J9VMInternals.java:167)
      at java.lang.J9VMInternals.initialize(J9VMInternals.java:167)
      at java.lang.J9VMInternals.initialize(J9VMInternals.java:167)
      at java.lang.J9VMInternals.initialize(J9VMInternals.java:167)
      at java.lang.J9VMInternals.initialize(J9VMInternals.java:167)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:60)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37)
      at java.lang.reflect.Method.invoke(Method.java:611)
      at net.sf.cglib.proxy.Enhancer.setCallbacksHelper(Enhancer.java:619)
      at net.sf.cglib.proxy.Enhancer.setThreadCallbacks(Enhancer.java:612)
      at net.sf.cglib.proxy.Enhancer.registerCallbacks(Enhancer.java:581)
      at org.easymock.internal.ClassProxyFactory.createProxy(ClassProxyFactory.java:189)
      ... 36 more
  </code></pre>