Java 模拟系统类时 Mockito + PowerMock LinkageError
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Mockito + PowerMock LinkageError while mocking system class
提问by Wojciech Reszelewski
I've got such a code snippet:
我有这样的代码片段：
@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:
在运行此测试时，我得到：
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.CodeCoverCoverageCounterya5ud0ow79ijrr1dvjrp4nxx60qhxeua02ta2fzpmb1d.<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$PowerMockJUnit44MethodRunner.runTestMethod(PowerMockJUnit44RunnerDelegateImpl.java:312)
at org.junit.internal.runners.MethodRoadie.run(MethodRoadie.java:86)
at org.junit.internal.runners.MethodRoadie.runBeforesThenTestThenAfters(MethodRoadie.java:94)
at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$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.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:
你知道我怎样才能防止这种情况吗？我也许还有另一种方法来模拟这样一段代码：
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
...
Enumeration<URL> resources = classLoader.getResources(path);
采纳答案by crandrad
Try adding this annotation to your Test class:
尝试将此注释添加到您的 Test 类：
@PowerMockIgnore("javax.management.*")
@PowerMockIgnore("javax.management.*")
Worked for me.
为我工作。
回答by ash
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.classbecause it is required during JVM startup - well before PowerMock can instrument.
为了模拟系统类，准备作为测试目标的类，而不是Thread.class. PowerMock 无法检测，Thread.class因为它在 JVM 启动期间是必需的 - 早在 PowerMock 可以检测之前。
The way instrumentation works, once a class is loaded, it can no longer be intstrumented.
检测的工作方式是，一旦加载了一个类，就不能再对其进行检测。
See the PowerMock wiki.
请参阅PowerMock 维基。
回答by u3530358
Classloaderconflict, use this: @PowerMockIgnore("javax.management.*")
类加载器冲突，使用这个：@PowerMockIgnore("javax.management.*")
Let mock classloaderdo not load javax.*.It works.
让模拟类加载器不加载javax.*.它的工作原理。
回答by Rens Groenveld
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).
这可能是一个老话题，但我也遇到了这个问题。事实证明，当 powermock 发现同一个包中有 2 个同名的类（通过不同的依赖项）时，某些 java 版本无法处理 powermockito。
With any version higher than Java 7_25 it gives this error.
任何高于 Java 7_25 的版本都会出现此错误。
回答by Jason D
Similar to the accepted response here, I ended up having to exclude all of the SSL related classes:
与此处接受的响应类似，我最终不得不排除所有与 SSL 相关的类：
@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.
将它添加到我的班级的顶部解决了错误。
回答by user3474985
In PowerMock 1.7.0 a user-defined global configuration can be added to your project's classpath. PowerMockConfig
在 PowerMock 1.7.0 中，可以将用户定义的全局配置添加到项目的类路径中。电源模拟配置
org/powermock/extensions/configuration.properties
Simply add a line in the properties file like:
只需在属性文件中添加一行，例如：
powermock.global-ignore=javax.management.*
This will resolve the error for all the test classes in your project.
这将解决项目中所有测试类的错误。
