我正在使用MRUnit测试MultipleOutputs。测试用例失败，并显示以下消息。
java.lang.ClassCastException: org.apache.hadoop.io.serializer.WritableSerialization cannot be cast to org.apache.hadoop.io.serializer.Serialization
我根据看到的示例使用以下注释。
@RunWith(PowerMockRunner.class)
@PrepareForTest({MultipleOutputs.class, LoadMapper.class, LoadReducer.class})
作为参考，我添加了用于测试的代码。
@RunWith(PowerMockRunner.class)
@PrepareForTest({MultipleOutputs.class, LoadMapper.class, LoadReducer.class})
@PowerMockIgnore({
"org.apache.log4j.*",
"javax.xml.*",
"org.xml.sax.*",
"org.apache.xerces.*",
"org.w3c.dom.*"
})
public class LoadTest extends LoadReducer {
MapDriver<LongWritable, Text, NullWritable, Text> mapDriver;
Configuration conf = new Configuration();
@SuppressWarnings("deprecation")
@Before
public void setUp() {
conf.set(LoadConstants.START_TAG_KEY, LoadConstants.START_TAG_KEY);
conf.set(LoadConstants.END_TAG_KEY, LoadConstants.END_TAG_KEY);
LoadMapper loadMapper = new LoadMapper();
mapDriver = MapDriver.newMapDriver(loadMapper);
mapDriver.setConfiguration(conf);
}
@Test
public void testFailure() throws IOException {
String inputRecord = "";
String errorMsg = "";
mapDriver.withInput(new LongWritable(0), new Text(inputRecord))
.withMultiOutput(LoadConstants.BAD, NullWritable.get(), new Text(inputRecord + errorMsg))
.runTest();
}
}
错误的堆栈跟踪如下:
java.lang.LinkageError: loader constraint violation: when resolving method "org.apache.hadoop.io.serializer.SerializationFactory.<init>(Lorg/apache/hadoop/conf/Configuration;)V" the class loader (instance of org/powermock/core/classloader/MockClassLoader) of the current class, org/apache/hadoop/mrunit/internal/io/Serialization, and the class loader (instance of sun/misc/Launcher$AppClassLoader) for the method's defining class, org/apache/hadoop/io/serializer/SerializationFactory, have different Class objects for the type org/apache/hadoop/conf/Configuration used in the signature
at org.apache.hadoop.mrunit.internal.io.Serialization.<init>(Serialization.java:39)
at org.apache.hadoop.mrunit.TestDriver.getSerialization(TestDriver.java:530)
at org.apache.hadoop.mrunit.TestDriver.copy(TestDriver.java:675)
at org.apache.hadoop.mrunit.TestDriver.copyPair(TestDriver.java:679)
at org.apache.hadoop.mrunit.MapDriverBase.addInput(MapDriverBase.java:120)
at org.apache.hadoop.mrunit.MapDriverBase.withInput(MapDriverBase.java:210)
at x.x.x.LoadTest.testFailure(LoadTest.java:20)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.junit.internal.runners.TestMethod.invoke(TestMethod.java:66)
at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$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: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.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
为MRUnit添加了POM依赖项:
<dependency>
<groupId>org.apache.mrunit</groupId>
<artifactId>mrunit</artifactId>
<version>1.1.0</version>
<classifier>hadoop2</classifier>
</dependency>
如果有人遇到此问题，请提供帮助。
最佳答案
从测试类中删除mapDriver.setConfiguration时，此问题已解决。
@SuppressWarnings("deprecation")
@Before
public void setUp() {
conf.set(LoadConstants.START_TAG_KEY, LoadConstants.START_TAG_KEY);
conf.set(LoadConstants.END_TAG_KEY, LoadConstants.END_TAG_KEY);
LoadMapper loadMapper = new LoadMapper();
mapDriver = MapDriver.newMapDriver(loadMapper);
mapDriver.setConfiguration(conf); // Removed this line
}
我不确定原因。