[英]MRUnit test giving NULLPOINTER exception while writing to HDFS using MULTIPLEOUTPUTS
I currently have a mapReduce program that send data to hdfs with different file name.So in my reducer I am using MultipleOutputs to write to different files in HDFS (Full Reducer code below). 我目前有一个mapReduce程序,它使用不同的文件名将数据发送到hdfs.So在我的reducer中我使用MultipleOutputs写入HDFS中的不同文件(下面的完全减速器代码)。
I would like to test my code using mrunit and below is my test method. 我想用mrunit测试我的代码,下面是我的测试方法。
@Test
public void reducerMRUnit() throws IOException{
String output="";
ArrayList<Text> list = new ArrayList<Text>(0);
list.add(new Text(""));
reduceDriver.withInput(new Text(""), list);
reduceDriver.withPathOutput(new Text(output),NullWritable.get(),"");
reduceDriver.runTest();
}
But, when I run this test it giving me NPE. 但是,当我运行此测试时,它给了我NPE。
java.lang.NullPointerException
at org.apache.hadoop.fs.Path.<init>(Path.java:104)
at org.apache.hadoop.fs.Path.<init>(Path.java:93)
at org.apache.hadoop.mapreduce.lib.output.FileOutputFormat.getDefaultWorkFile(FileOutputFormat.java:286)
at org.apache.hadoop.mapreduce.lib.output.TextOutputFormat.getRecordWriter(TextOutputFormat.java:129)
at org.apache.hadoop.mapreduce.lib.output.MultipleOutputs.getRecordWriter(MultipleOutputs.java:476)
at org.apache.hadoop.mapreduce.lib.output.MultipleOutputs.write(MultipleOutputs.java:456)
at org.clinical3PO.learn.fasta.ArffToFastAReducer.reduce(ArffToFastAReducer.java:127)
at org.clinical3PO.learn.fasta.ArffToFastAReducer.reduce(ArffToFastAReducer.java:1)
at org.apache.hadoop.mapreduce.Reducer.run(Reducer.java:171)
at org.apache.hadoop.mrunit.mapreduce.ReduceDriver.run(ReduceDriver.java:265)
at org.apache.hadoop.mrunit.TestDriver.runTest(TestDriver.java:640)
at org.apache.hadoop.mrunit.TestDriver.runTest(TestDriver.java:627)
at org.clinical3PO.learn.fasta.MRUnitTest.ArffToFastAReducerMRUnitTest.reducerMRUnit(ArffToFastAReducerMRUnitTest.java:63)
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:497)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:76)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
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:459)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
Reducer code: 减速机代码:
import java.io.IOException;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.output.MultipleOutputs;
public class AReducer extends Reducer<Text, Text, Text, NullWritable>{
private MultipleOutputs<Text, NullWritable> mos = null;
@Override
public void setup(Context context) throws IOException {
mos = new MultipleOutputs<Text, NullWritable>(context);
}
@Override
public void reduce(Text key, Iterable<Text> values, Context context)
throws IOException, InterruptedException {
mos = new MultipleOutputs<Text, NullWritable>(context);
mos.write(key, value, "filename");
}
@Override
public void cleanup(Context context) throws IOException, InterruptedException {
mos.close();
}
}
Any Suggestions? 有什么建议么?
MRUnit currently has a known issue, which is not well documented, that testing MultipleOutputs
requires running the test with PowerMockRunner
and a PrepareForTest
annotation applied to mock the reducer class. MRUnit目前有一个已知问题,没有详细记录,测试MultipleOutputs
需要使用PowerMockRunner
运行测试并应用PrepareForTest
注释来模拟reducer类。 JIRA issues MRUNIT-13 and MRUNIT-213 contain detailed discussion of this. JIRA问题MRUNIT-13和MRUNIT-213包含对此的详细讨论。 MRUNIT-213 is still unresolved/unfixed. MRUNIT-213仍未解决/未解决。
Adding PowerMock to the project then triggers some further challenges in lining up the right compatible versions of Mockito and PowerMock. 将PowerMock添加到项目中会在排列Mockito和PowerMock的正确兼容版本时引发一些进一步的挑战。 The documentation on Using PowerMock with Mockito covers which versions are compatible. 使用PowerMock和Mockito的文档涵盖了哪些版本兼容。
I tried making these changes to your sample. 我尝试对您的样本进行这些更改。 That got past the NullPointerException
, but then I ran into one final problem. 这超过了NullPointerException
,但后来我遇到了一个最后的问题。 The expected path output declared in the test did not match up with the "filename"
path used by the reducer code. 测试中声明的预期路径输出与reducer代码使用的"filename"
路径不匹配。 I changed the expected path output to get the test completely passing. 我更改了预期的路径输出以使测试完全通过。
Here is my final result: a fully working project with your sample test. 这是我的最终结果:一个完整的项目与您的样品测试。 Enjoy! 请享用!
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>test</groupId>
<artifactId>test-mrunit</artifactId>
<packaging>jar</packaging>
<version>0.0.1-SNAPSHOT</version>
<name>Test MRUnit</name>
<description>Test MRUnit</description>
<properties>
<hadoop.version>2.7.1</hadoop.version>
<powermock.version>1.6.4</powermock.version>
</properties>
<dependencies>
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-common</artifactId>
<version>${hadoop.version}</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-mapreduce-client-core</artifactId>
<version>${hadoop.version}</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.mockito</groupId>
<artifactId>mockito-all</artifactId>
<version>1.10.19</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.powermock</groupId>
<artifactId>powermock-core</artifactId>
<version>${powermock.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.powermock</groupId>
<artifactId>powermock-module-junit4</artifactId>
<version>${powermock.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.powermock</groupId>
<artifactId>powermock-api-mockito</artifactId>
<version>${powermock.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.apache.mrunit</groupId>
<artifactId>mrunit</artifactId>
<version>1.1.0</version>
<classifier>hadoop2</classifier>
<scope>test</scope>
</dependency>
</dependencies>
</project>
import java.io.IOException;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.output.MultipleOutputs;
public class AReducer extends Reducer<Text, Text, Text, NullWritable>{
private MultipleOutputs<Text, NullWritable> mos = null;
@Override
public void setup(Context context) throws IOException {
mos = new MultipleOutputs<Text, NullWritable>(context);
}
@Override
public void reduce(Text key, Iterable<Text> values, Context context)
throws IOException, InterruptedException {
mos.write(key, NullWritable.get(), "filename");
}
@Override
public void cleanup(Context context) throws IOException, InterruptedException {
mos.close();
}
}
import java.io.IOException;
import java.util.ArrayList;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mrunit.mapreduce.ReduceDriver;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;
@RunWith(PowerMockRunner.class)
@PrepareForTest(AReducer.class)
public class TestAReducer {
@Test
public void reducerMRUnit() throws IOException{
ReduceDriver reduceDriver = new ReduceDriver(new AReducer());
String output = "";
ArrayList<Text> list = new ArrayList<Text>(0);
list.add(new Text(""));
reduceDriver.withInput(new Text(""), list);
reduceDriver.withPathOutput(new Text(output), NullWritable.get(), "filename");
reduceDriver.runTest();
}
}
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