hadoop类未找到异常，即使它在hadoop类路径中

Question

Just installed hadoop and have a simple program below which I found online to display the configurations

import java.util.*;
import org.apache.hadoop.conf.*;

class printHadoop {

  public static void main(String args[]) {
    Configuration conf = new Configuration();
    if ( args.length == 1)
      conf.addResource(args[0]);
    Iterator it = conf.iterator();
    while (it.hasNext()) {
      System.out.println(it.next());
    }
  }
}

I compiled it and tried to run it through hadoop

$hadoop -cp . printHadoop

It throws a classnotfound error , its not able to find the org.apache.hadoop.conf.* which are in hadoop folder

But when I look at the classpath for hadoop

$hadoop classpath

It does include the jars that contain the required packages.

/usr/local/hadoop/libexec/../conf:/usr/lib/jvm/java-6-openjdk-amd64/lib/tools.jar:/usr/local/hadoop/libexec/..:/usr/local/hadoop/libexec/../hadoop-core-1.0.4.jar:/usr/local/hadoop/libexec/../lib/asm-3.2.jar:/usr/local/hadoop/libexec/../lib/aspectjrt-1.6.5.jar:/usr/local/hadoop/libexec/../lib/aspectjtools-1.6.5.jar:/usr/local/hadoop/libexec/../lib/commons-beanutils-1.7.0.jar:/usr/local/hadoop/libexec/../lib/commons-beanutils-core-1.8.0.jar:/usr/local/hadoop/libexec/../lib/commons-cli-1.2.jar:/usr/local/hadoop/libexec/../lib/commons-codec-1.4.jar:/usr/local/hadoop/libexec/../lib/commons-collections-3.2.1.jar:/usr/local/hadoop/libexec/../lib/commons-configuration-1.6.jar:/usr/local/hadoop/libexec/../lib/commons-daemon-1.0.1.jar:/usr/local/hadoop/libexec/../lib/commons-digester-1.8.jar:/usr/local/hadoop/libexec/../lib/commons-el-1.0.jar:/usr/local/hadoop/libexec/../lib/commons-httpclient-3.0.1.jar:/usr/local/hadoop/libexec/../lib/commons-io-2.1.jar:/usr/local/hadoop/libexec/../lib/commons-lang-2.4.jar:/usr/local/hadoop/libexec/../lib/commons-logging-1.1.1.jar:/usr/local/hadoop/libexec/../lib/commons-logging-api-1.0.4.jar:/usr/local/hadoop/libexec/../lib/commons-math-2.1.jar:/usr/local/hadoop/libexec/../lib/commons-net-1.4.1.jar:/usr/local/hadoop/libexec/../lib/core-3.1.1.jar:/usr/local/hadoop/libexec/../lib/hadoop-capacity-scheduler-1.0.4.jar:/usr/local/hadoop/libexec/../lib/hadoop-fairscheduler-1.0.4.jar:/usr/local/hadoop/libexec/../lib/hadoop-thriftfs-1.0.4.jar:/usr/local/hadoop/libexec/../lib/hsqldb-1.8.0.10.jar:/usr/local/hadoop/libexec/../lib/jackson-core-asl-1.8.8.jar:/usr/local/hadoop/libexec/../lib/jackson-mapper-asl-1.8.8.jar:/usr/local/hadoop/libexec/../lib/jasper-compiler-5.5.12.jar:/usr/local/hadoop/libexec/../lib/jasper-runtime-5.5.12.jar:/usr/local/hadoop/libexec/../lib/jdeb-0.8.jar:/usr/local/hadoop/libexec/../lib/jersey-core-1.8.jar:/usr/local/hadoop/libexec/../lib/jersey-json-1.8.jar:/usr/local/hadoop/libexec/../lib/jersey-server-1.8.jar:/usr/local/hadoop/libexec/../lib/jets3t-0.6.1.jar:/usr/local/hadoop/libexec/../lib/jetty-6.1.26.jar:/usr/local/hadoop/libexec/../lib/jetty-util-6.1.26.jar:/usr/local/hadoop/libexec/../lib/jsch-0.1.42.jar:/usr/local/hadoop/libexec/../lib/junit-4.5.jar:/usr/local/hadoop/libexec/../lib/kfs-0.2.2.jar:/usr/local/hadoop/libexec/../lib/log4j-1.2.15.jar:/usr/local/hadoop/libexec/../lib/mockito-all-1.8.5.jar:/usr/local/hadoop/libexec/../lib/oro-2.0.8.jar:/usr/local/hadoop/libexec/../lib/servlet-api-2.5-20081211.jar:/usr/local/hadoop/libexec/../lib/slf4j-api-1.4.3.jar:/usr/local/hadoop/libexec/../lib/slf4j-log4j12-1.4.3.jar:/usr/local/hadoop/libexec/../lib/xmlenc-0.52.jar:/usr/local/hadoop/libexec/../lib/jsp-2.1/jsp-2.1.jar:/usr/local/hadoop/libexec/../lib/jsp-2.1/jsp-api-2.1.jar

Any Idea why the classnotfound exception is happening when all the required jars are displayed above?

Answer 1

Rather than using hadoop -cp . printHadoop hadoop -cp . printHadoop , try hadoop jar . printHadoop hadoop jar . printHadoop having done the following first:

export HADOOP_CLASSPATH=$HADOOP_CLASSPATH:`echo *.jar`:`echo lib/*.jar | sed 's/ /:/g'`

This will add all jars found in the current directory (and the lib directory if you have one) to the classpath.

Answer 2

As I can see from your question you're trying to use completely wrong syntax. Correct should be:

hadoop jar <your-jar> printHadoop