我想运行我在 Mahout In Action 中找到的这段代码:
package org.help;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.SequenceFile;
import org.apache.hadoop.io.Text;
import org.apache.mahout.math.DenseVector;
import org.apache.mahout.math.NamedVector;
import org.apache.mahout.math.VectorWritable;
public class SeqPrep {
public static void main(String args[]) throws IOException{
List<NamedVector> apples = new ArrayList<NamedVector>();
NamedVector apple;
apple = new NamedVector(new DenseVector(new double[]{0.11, 510, 1}), "small round green apple");
apples.add(apple);
Configuration conf = new Configuration();
FileSystem fs = FileSystem.get(conf);
Path path = new Path("appledata/apples");
SequenceFile.Writer writer = new SequenceFile.Writer(fs, conf, path, Text.class, VectorWritable.class);
VectorWritable vec = new VectorWritable();
for(NamedVector vector : apples){
vec.set(vector);
writer.append(new Text(vector.getName()), vec);
}
writer.close();
SequenceFile.Reader reader = new SequenceFile.Reader(fs, new Path("appledata/apples"), conf);
Text key = new Text();
VectorWritable value = new VectorWritable();
while(reader.next(key, value)){
System.out.println(key.toString() + " , " + value.get().asFormatString());
}
reader.close();
}
}
我编译它:
$ javac -classpath :/usr/local/hadoop-1.0.3/hadoop-core-1.0.3.jar:/home/hduser/mahout/trunk/core/target/mahout-core-0.8-SNAPSHOT.jar:/home/hduser/mahout/trunk/core/target/mahout-core-0.8-SNAPSHOT-job.jar:/home/hduser/mahout/trunk/core/target/mahout-core-0.8-SNAPSHOT-sources.jar -d myjavac/ SeqPrep.java
我把它装 jar 了:
$ jar -cvf SeqPrep.jar -C myjavac/ .
现在我想在本地 hadoop 节点上运行它。我试过:
hadoop jar SeqPrep.jar org.help.SeqPrep
但是我得到:
Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/mahout/math/Vector
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:247)
at org.apache.hadoop.util.RunJar.main(RunJar.java:149)
所以我尝试使用 libjars 参数:
$ hadoop jar SeqPrep.jar org.help.SeqPrep -libjars /home/hduser/mahout/trunk/core/target/mahout-core-0.8-SNAPSHOT.jar -libjars /home/hduser/mahout/trunk/core/target/mahout-core-0.8-SNAPSHOT-job.jar -libjars /home/hduser/mahout/trunk/core/target/mahout-core-0.8-SNAPSHOT-sources.jar -libjars /home/hduser/mahout/trunk/math/target/mahout-math-0.8-SNAPSHOT.jar -libjars /home/hduser/mahout/trunk/math/target/mahout-math-0.8-SNAPSHOT-sources.jar
遇到了同样的问题。我不知道还能尝试什么。
我的最终目标是能够将 hadoop fs 上的 .csv 文件读入稀疏矩阵,然后将其乘以随机 vector 。
编辑: 看起来 Razvan 明白了(注意:请参阅下面的另一种不会干扰您的 hadoop 安装的方法)。供引用:
$ find /usr/local/hadoop-1.0.3/. |grep mah
/usr/local/hadoop-1.0.3/./lib/mahout-core-0.8-SNAPSHOT-tests.jar
/usr/local/hadoop-1.0.3/./lib/mahout-core-0.8-SNAPSHOT.jar
/usr/local/hadoop-1.0.3/./lib/mahout-core-0.8-SNAPSHOT-job.jar
/usr/local/hadoop-1.0.3/./lib/mahout-core-0.8-SNAPSHOT-sources.jar
/usr/local/hadoop-1.0.3/./lib/mahout-math-0.8-SNAPSHOT-sources.jar
/usr/local/hadoop-1.0.3/./lib/mahout-math-0.8-SNAPSHOT-tests.jar
/usr/local/hadoop-1.0.3/./lib/mahout-math-0.8-SNAPSHOT.jar
然后:
$hadoop jar SeqPrep.jar org.help.SeqPrep
small round green apple , small round green apple:{0:0.11,1:510.0,2:1.0}
编辑:我试图在不将 mahout jar 复制到 hadoop 库中的情况下执行此操作/
$ rm /usr/local/hadoop-1.0.3/lib/mahout-*
当然还有:
hadoop jar SeqPrep.jar org.help.SeqPrep
Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/mahout/math/Vector
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:247)
at org.apache.hadoop.util.RunJar.main(RunJar.java:149)
Caused by: java.lang.ClassNotFoundException: org.apache.mahout.math.Vector
at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
当我尝试 mahout 作业文件时:
$hadoop jar ~/mahout/trunk/core/target/mahout-core-0.8-SNAPSHOT-job.jar org.help.SeqPrep
Exception in thread "main" java.lang.ClassNotFoundException: org.help.SeqPrep
at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:247)
at org.apache.hadoop.util.RunJar.main(RunJar.java:149)
如果我尝试包含我制作的 .jar 文件:
$ hadoop jar ~/mahout/trunk/core/target/mahout-core-0.8-SNAPSHOT-job.jar SeqPrep.jar org.help.SeqPrep
Exception in thread "main" java.lang.ClassNotFoundException: SeqPrep.jar
编辑:显然我一次只能发送一个 jar 到 hadoop。这意味着我需要将我创建的类添加到 mahout 核心作业文件中:
~/mahout/trunk/core/target$ cp mahout-core-0.8-SNAPSHOT-job.jar mahout-core-0.8-SNAPSHOT-job.jar_backup
~/mahout/trunk/core/target$ cp ~/workspace/seqprep/bin/org/help/SeqPrep.class .
~/mahout/trunk/core/target$ jar uf mahout-core-0.8-SNAPSHOT-job.jar SeqPrep.class
然后:
~/mahout/trunk/core/target$ hadoop jar mahout-core-0.8-SNAPSHOT-job.jar org.help.SeqPrep
Exception in thread "main" java.lang.ClassNotFoundException: org.help.SeqPrep
编辑: 好的,现在我可以在不影响我的 hadoop 安装的情况下完成它。我在之前的编辑中错误地更新了 .jar。应该是:
~/mahout/trunk/core/target$ jar uf mahout-core-0.8-SNAPSHOT-job.jar org/help/SeqPrep.class
然后:
~/mahout/trunk/core/target$ hadoop jar mahout-core-0.8-SNAPSHOT-job.jar org.help.SeqPrep
small round green apple , small round green apple:{0:0.11,1:510.0,2:1.0}
最佳答案
您需要使用 Mahout 提供的“作业”JAR 文件。它打包了所有依赖项。您也需要将您的类(class)添加到其中。这就是所有 Mahout 示例的工作方式。您不应该将 Mahout jar 放在 Hadoop 库中,因为那样会将程序“安装”到 Hadoop 中太深。
关于java - 如何构建/运行这个简单的 Mahout 程序而不出现异常?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/11479600/