Mockito + PowerMock LinkageError while mocking system class

Question

I've got such a code snippet:

@RunWith(PowerMockRunner.class)
@PrepareForTest({Thread.class})
public class AllMeasuresDataTest {

@Before
public void setUp() throws Exception {
}

@Test
public void testGetMeasures() {
    AllMeasuresData measure = new AllMeasuresData();
    assertEquals(measure.getMeasures(), null);
    HashMap<String, Measure> map = new HashMap<String, Measure>();
    measure.setMeasures(map);
    assertEquals(measure.getMeasures(), map);
    measure.setMeasures(null);
    assertEquals(measure.getMeasures(), null);
}

@Test
public void testAllMeasuresData() throws IOException {
    ClassLoader loader = PowerMockito.mock(ClassLoader.class);
    Thread threadMock = PowerMockito.mock(Thread.class);
    Vector<URL> vec = new Vector<URL>();
    Mockito.when(loader.getResources("measure")).thenReturn(vec.elements());
    Mockito.when(threadMock.getContextClassLoader()).thenReturn(loader);
    PowerMockito.mockStatic(Thread.class);
    Mockito.when(Thread.currentThread()).thenReturn(threadMock);
        ...
    }
}

While running this tests I got:

java.lang.LinkageError: loader constraint violation: loader (instance of org/powermock/core/classloader/MockClassLoader) 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:791)
at java.lang.ClassLoader.defineClass(ClassLoader.java:634)
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:356)
at org.codecover.instrumentation.java.measurement.ProtocolImpl.initializeMBean(ProtocolImpl.java:247)
at org.codecover.instrumentation.java.measurement.ProtocolImpl.<init>(ProtocolImpl.java:237)
at org.codecover.instrumentation.java.measurement.ProtocolImpl.getInstance(ProtocolImpl.java:185)
at measure.CodeCoverCoverageCounter$6ya5ud0ow79ijrr1dvjrp4nxx60qhxeua02ta2fzpmb1d.<clinit>(MeasureCalculatorsHolder.java:146)
at measure.MeasureCalculatorsHolder.<clinit>(MeasureCalculatorsHolder.java:17)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:188)
at javassist.runtime.Desc.getClassObject(Desc.java:43)
at javassist.runtime.Desc.getClassType(Desc.java:152)
at javassist.runtime.Desc.getType(Desc.java:122)
at javassist.runtime.Desc.getType(Desc.java:78)
at algorithm.AllMeasuresDataTest.testGetMeasures(AllMeasuresDataTest.java:26)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.junit.internal.runners.TestMethod.invoke(TestMethod.java:66)
at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.runTestMethod(PowerMockJUnit44RunnerDelegateImpl.java:312)
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:296)
at org.powermock.modules.junit4.internal.impl.PowerMockJUnit49RunnerDelegateImpl$PowerMockJUnit49MethodRunner.executeTestInSuper(PowerMockJUnit49RunnerDelegateImpl.java:116)
at org.powermock.modules.junit4.internal.impl.PowerMockJUnit49RunnerDelegateImpl$PowerMockJUnit49MethodRunner.executeTest(PowerMockJUnit49RunnerDelegateImpl.java:77)
at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.runBeforesThenTestThenAfters(PowerMockJUnit44RunnerDelegateImpl.java:284)
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:209)
at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.runMethods(PowerMockJUnit44RunnerDelegateImpl.java:148)
at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$1.run(PowerMockJUnit44RunnerDelegateImpl.java:122)
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:120)
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:50)
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.codecover.juniteclipse.runner.EclipseTestRunner.main(EclipseTestRunner.java:40)

Do you know how can I prevent this? I maybe there is another way to mock such a piece of code:

ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
...
Enumeration<URL> resources = classLoader.getResources(path);

First test is getters and setters test, I'm calling constructor there (and there the exception occurs). The second one is constructor test. I want to get control of what resources enumeration contains in third code snippet. — Wojciech Reszelewski, May 13 '13 at 11:20
First of all, it looks to me that your tests are very tightly coupled to your implementation. By experience, this will lead to fragile tests. Preferrably, you want to think "black box" when writing your tests. "What is this piece of code supposed to do", rather than "How is this piece of code doing it". Second, I think you'd be better off just creating a set of resources and let the Java runtime deal with the classloading itself. — NilsH, May 13 '13 at 11:22
It is possible to create various sets of resources, as they where test cases? — Wojciech Reszelewski, May 13 '13 at 11:30
Sure. The easiest for you is probably to parametrize the name of the resources. Then you can pass different resource names into your tests. — NilsH, May 13 '13 at 11:34
You mean creating another method with new parameters? It's strange, but I'm writing tests for project that's already complete, but tests are missing, so it's not so easy in that case. — Wojciech Reszelewski, May 13 '13 at 11:56

crandrad · Accepted Answer · 2015-11-22T05:11:28.433

483

Try adding this annotation to your Test class:

@PowerMockIgnore("javax.management.*")

Worked for me.

edited Nov 22 '15 at 05:11

answered Jan 21 '14 at 20:06

crandrad

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precision *"to your Test Class". Simple and usefull answer ! – pdem Nov 19 '15 at 10:09
3

Can this be done by code or config as well? I could not find any way to do this. We have hundreds of tests ... i can not adjust them all. – Frederic Leitenberger Jul 11 '17 at 18:01
1

@FredericLeitenberger see my answer below – user3474985 Jan 03 '19 at 23:43
6

Can you please also explain the intution and meaning of this fix? What instruction are we giving to PowerMockito using that line? – Swapnil B. Oct 05 '19 at 01:41

Jason D · Answer 2 · 2019-05-15T17:59:28.170

38

Similar to the accepted response here, I ended up having to exclude all of the SSL related classes:

@PowerMockIgnore({"javax.management.*", "org.apache.http.conn.ssl.*", "com.amazonaws.http.conn.ssl.*", "javax.net.ssl.*"})

Adding that to the top of my class resolved the error.

edited May 15 '19 at 17:59

answered Jul 22 '16 at 18:31

Jason D

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Still needed to add some more paths but you saved my life man! `@PowerMockIgnore({"javax.management.*", "org.apache.http.conn.ssl.*", "com.amazonaws.*", "javax.net.ssl.*","com.sun.*"})` – Francisco López-Sancho Aug 04 '16 at 12:29
Good to know about com.sun too. – Jason D Aug 04 '16 at 14:04
2

I needed the following: @PowerMockIgnore({"javax.management.*", "javax.crypto.*"}) – Kristof Neirynck Jun 12 '17 at 10:29
3

This one saved me: @PowerMockIgnore({"javax.management.*", "org.apache.http.*", "com.amazonaws.http.conn.ssl.*", "javax.net.ssl.*", "com.sun.*", "javax.xml.*", "javax.crypto.*"}) – Fayaz Ahmed Apr 05 '19 at 00:22

score 29 · Answer 3 · edited Apr 14 '14 at 02:38

29

Classloader conflict, use this: @PowerMockIgnore("javax.management.*")

Let mock classloader do not load javax.*. It works.

edited Apr 14 '14 at 02:38

Logan Wayne

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answered Apr 14 '14 at 02:10

烬哥哥

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After using `@PowerMockIgnore("javax.management.*")`, the test class works well singly. But running as `Junit test` on that **package** got `Failed to load ApplicationContext` error. `org.apache.catalina.LifecycleException: A child container failed during start` and so on. – niaomingjian May 22 '17 at 10:23

score 8 · Answer 4 · answered Dec 12 '14 at 08:38

8

This may be a bit of an old topic, but I have also ran into this problem. Turns out that some of the java versions cannot handle powermockito when powermock finds out there are 2 classes with the same name in the same package (over different dependencies).

With any version higher than Java 7_25 it gives this error.

answered Dec 12 '14 at 08:38

Rens Groenveld

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"With any version higher than Java 7_25 it gives this error.", This is informative. – Kajal Sinha Jun 16 '16 at 02:08
What it means: "cannot handle powermockito"? Is there any way to deal with it besides ignoring by annotation? – Line May 19 '17 at 07:27
It's a long time ago, but I think we sorted it out by making sure there are not 2 classes with the same name in the same kind of package. Of course, if you have 2 libraries you depend on, and they reside in there... it is going to be difficult. I don't know if this issue has been fixed in the meantime. – Rens Groenveld May 19 '17 at 11:28

score 8 · Answer 5 · answered Jan 03 '19 at 23:41

8

In PowerMock 1.7.0 a user-defined global configuration can be added to your project's classpath. PowerMockConfig

org/powermock/extensions/configuration.properties

Simply add a line in the properties file like:

powermock.global-ignore=javax.management.*

This will resolve the error for all the test classes in your project.

answered Jan 03 '19 at 23:41

user3474985

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Note, spaces and double quotes are not allowed in the configuration.properties file. See: https://github.com/powermock/powermock/issues/989 – Navigatron Sep 28 '21 at 08:38

score 5 · Answer 6 · edited Jul 03 '17 at 20:03

5

In order to mock system classes, prepare the class that is the target of the test, not Thread.class. There's no way PowerMock will be able to instrument Thread.class because it is required during JVM startup - well before PowerMock can instrument.

The way instrumentation works, once a class is loaded, it can no longer be intstrumented.

See the PowerMock wiki.

edited Jul 03 '17 at 20:03

try-catch-finally

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answered Aug 31 '13 at 19:17

ash

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score 5 · Answer 7 · answered Feb 03 '21 at 12:06

5

Depending on your individual setup, it may be necessary to add more methods to @PowerMockIgnore. I stumbled over this with slf4j, for using PowerMock and slf4j together, you'll need

@PowerMockIgnore({ "com.sun.org.apache.xerces.*", "javax.xml.*", "org.xml.*", "javax.management.*", "org.w3c.dom.*" })

answered Feb 03 '21 at 12:06

David Georg Reichelt

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Compared to other examples of `@PowerMockIgnore` , this one worked for me, because of the `"org.xml.*"` entry. Others with this issue should check, which signature issues arise from PowerMock and Ignore those packages with the annotation. – Webchen Nov 30 '21 at 09:53

Mockito + PowerMock LinkageError while mocking system class

7 Answers7

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