目的是要跑通这个单元测试:hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestClose.java
这个Java文件比较简单:
/**
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* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
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package org.apache.hadoop.hdfs; import static org.junit.Assert.fail; import java.io.IOException;
import java.io.OutputStream;
import java.nio.channels.ClosedChannelException; import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.test.GenericTestUtils;
import org.junit.Test; public class TestClose { @Test
public void testWriteAfterClose() throws IOException {
Configuration conf = new Configuration();
MiniDFSCluster cluster = new MiniDFSCluster.Builder(conf)
.build(); try {
final byte[] data = "foo".getBytes(); FileSystem fs = FileSystem.get(conf);
OutputStream out = fs.create(new Path("/test")); out.write(data);
out.close();
try {
// Should fail.
out.write(data);
fail("Should not have been able to write more data after file is closed.");
} catch (ClosedChannelException cce) {
// We got the correct exception. Ignoring.
}
// Should succeed. Double closes are OK.
out.close();
} finally {
if (cluster != null) {
cluster.shutdown();
}
}
} }
通过实例化一个minicluster来测试hdfs的关闭功能是否正常。
直接运行Junit,将会报错,因为在CLASSPATH中找不到webapps/hdfs。
正确的做法(https://hadoop.apache.org/docs/current/hadoop-project-dist/hadoop-common/CLIMiniCluster.html )
要现在~/CVS/hadoop目录下执行如下两条命令:
hadoop@ubuntu:~/CVS/hadoop$ mvn clean install –DskipTests
hadoop@ubuntu:~/CVS/hadoop$ mvn package -Pdist -Dtar -DskipTests -Dmaven.javadoc.skip
执行完这两条命令后,会在如下目录生成webapps目录:
也就是说这个webapps目录是通过上面两条命令生成的,如果没有执行上面两条命令,那么这个目录下就不会有这个文件,导致java在运行时无法在CLASSPATH中找到这个文件夹。一切准备就绪,运行Junit,可以看到单元测试成功通过: