我是刚开始编写Hadoop代码的新手，并且知道此问题已被多次回答。但是，我仍然很难找出正确的类路径来编译WordCount.java代码。我正在运行CentOS版本7。
我的Hadoop版本是:
Hadoop 2.7.1 Subversion
https://git-wip-us.apache.org/repos/asf/hadoop.git -r 15ecc87ccf4a0228f35af08fc56de536e6ce657a
Compiled by jenkins on 2015-06-29T06:04Z
Compiled with protoc 2.5.0
From source with checksum fc0a1a23fc1868e4d5ee7fa2b28a58a
This command was run using /usr/local/hadoop/share/hadoop/common/hadoop-common-2.7.1.jar
当我回显$ PATH时，得到以下信息:
我正在运行的Java版本是:
java version "1.7.0_91"
OpenJDK Runtime Environment (rhel-2.6.2.1.el7_1-x86_64 u91-b00)
OpenJDK 64-Bit Server VM (build 24.91-b01, mixed mode)
我确实在vi .bashrc中设置了Java和Hadoop的所有环境变量，如下所示，并且jps通过了。 Java也可以与其他代码一起编译，但是我认为我弄错了Hadoop的类路径。
Java变量
export JAVA_HOME=/usr/lib/jvm/jre-1.7.0-openjdk/
export PATH=$PATH:$JAVA_HOME
Hadoop变量
export HADOOP_INSTALL=/usr/local/hadoop
export PATH=$PATH:$HADOOP_INSTALL/bin
export PATH=$PATH:$HADOOP_INSTALL/sbin
export HADOOP_MAPRED_HOME=$HADOOP_INSTALL
export HADOOP_COMMON_HOME=$HADOOP_INSTALL
export HADOOP_HDFS_HOME=$HADOOP_INSTALL
export YARN_HOME=$HADOOP_INSTALL
export HADOOP_COMMON_LIB_NATIVE_DIR=$HADOOP_INSTALL/lib/native
当我尝试在工作目录中编译WordCount.java时，出现这些错误:
WordCount.java:5: error: package org.apache.hadoop.conf does not exist
import org.apache.hadoop.conf.*;
^
WordCount.java:6: error: package org.apache.hadoop.fs does not exist
import org.apache.hadoop.fs.*;
^
WordCount.java:7: error: package org.apache.hadoop.conf does not exist
import org.apache.hadoop.conf.*;
^
WordCount.java:8: error: package org.apache.hadoop.io does not exist
import org.apache.hadoop.io.*;
^
WordCount.java:9: error: package org.apache.hadoop.mapreduce does not exist
import org.apache.hadoop.mapreduce.*;
^
WordCount.java:10: error: package org.apache.hadoop.mapreduce.lib.input does not exist
import org.apache.hadoop.mapreduce.lib.input.*;
^
WordCount.java:11: error: package org.apache.hadoop.mapreduce.lib.output does not exist
import org.apache.hadoop.mapreduce.lib.output.*;
^
WordCount.java:12: error: package org.apache.hadoop.util does not exist
import org.apache.hadoop.util.*;
^
WordCount.java:14: error: cannot find symbol
public class WordCount extends Configured implements Tool {
^
symbol: class Configured
WordCount.java:14: error: cannot find symbol
public class WordCount extends Configured implements Tool {
^
symbol: class Tool
WordCount.java:47: error: cannot find symbol
public static class Map extends Mapper<LongWritable, Text, Text, IntWritable> {
^
symbol: class Mapper
location: class WordCount
WordCount.java:47: error: cannot find symbol
public static class Map extends Mapper<LongWritable, Text, Text, IntWritable> {
^
symbol: class LongWritable
location: class WordCount
WordCount.java:47: error: cannot find symbol
public static class Map extends Mapper<LongWritable, Text, Text, IntWritable> {
^
symbol: class Text
location: class WordCount
WordCount.java:47: error: cannot find symbol
public static class Map extends Mapper<LongWritable, Text, Text, IntWritable> {
^
symbol: class Text
location: class WordCount
WordCount.java:47: error: cannot find symbol
public static class Map extends Mapper<LongWritable, Text, Text, IntWritable> {
^
symbol: class IntWritable
location: class WordCount
WordCount.java:48: error: cannot find symbol
private final static IntWritable one = new IntWritable(1);
^
symbol: class IntWritable
location: class Map
WordCount.java:49: error: cannot find symbol
private Text word = new Text();
^
symbol: class Text
location: class Map
WordCount.java:52: error: cannot find symbol
public void map(LongWritable key, Text value,
^
symbol: class LongWritable
location: class Map
WordCount.java:52: error: cannot find symbol
public void map(LongWritable key, Text value,
^
symbol: class Text
location: class Map
WordCount.java:53: error: package Mapper does not exist
Mapper.Context context) throws IOException, InterruptedException {
^
WordCount.java:63: error: cannot find symbol
public static class Reduce extends Reducer<Text, IntWritable, Text, IntWritable> {
^
symbol: class Reducer
location: class WordCount
WordCount.java:63: error: cannot find symbol
public static class Reduce extends Reducer<Text, IntWritable, Text, IntWritable> {
^
symbol: class Text
location: class WordCount
WordCount.java:63: error: cannot find symbol
public static class Reduce extends Reducer<Text, IntWritable, Text, IntWritable> {
^
symbol: class IntWritable
location: class WordCount
WordCount.java:63: error: cannot find symbol
public static class Reduce extends Reducer<Text, IntWritable, Text, IntWritable> {
^
symbol: class Text
location: class WordCount
WordCount.java:63: error: cannot find symbol
public static class Reduce extends Reducer<Text, IntWritable, Text, IntWritable> {
^
symbol: class IntWritable
location: class WordCount
WordCount.java:66: error: cannot find symbol
public void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {
^
symbol: class Text
location: class Reduce
WordCount.java:66: error: cannot find symbol
public void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {
^
symbol: class IntWritable
location: class Reduce
WordCount.java:66: error: cannot find symbol
public void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {
^
symbol: class Context
location: class Reduce
WordCount.java:17: error: cannot find symbol
int res = ToolRunner.run(new WordCount(), args);
^
symbol: variable ToolRunner
location: class WordCount
WordCount.java:22: error: cannot find symbol
Path inputPath = new Path(args[0]);
^
symbol: class Path
location: class WordCount
WordCount.java:22: error: cannot find symbol
Path inputPath = new Path(args[0]);
^
symbol: class Path
location: class WordCount
WordCount.java:23: error: cannot find symbol
Path outputPath = new Path(args[1]);
^
symbol: class Path
location: class WordCount
WordCount.java:23: error: cannot find symbol
Path outputPath = new Path(args[1]);
^
symbol: class Path
location: class WordCount
WordCount.java:25: error: cannot find symbol
Configuration conf = getConf();
^
symbol: class Configuration
location: class WordCount
WordCount.java:25: error: cannot find symbol
Configuration conf = getConf();
^
symbol: method getConf()
location: class WordCount
WordCount.java:26: error: cannot find symbol
Job job = new Job(conf, this.getClass().toString());
^
symbol: class Job
location: class WordCount
WordCount.java:26: error: cannot find symbol
Job job = new Job(conf, this.getClass().toString());
^
symbol: class Job
location: class WordCount
WordCount.java:26: error: cannot find symbol
Job job = new Job(conf, this.getClass().toString());
^
symbol: method getClass()
WordCount.java:28: error: cannot find symbol
FileInputFormat.setInputPaths(job, inputPath);
^
symbol: variable FileInputFormat
location: class WordCount
WordCount.java:29: error: cannot find symbol
FileOutputFormat.setOutputPath(job, outputPath);
^
symbol: variable FileOutputFormat
location: class WordCount
WordCount.java:33: error: cannot find symbol
job.setInputFormatClass(TextInputFormat.class);
^
symbol: class TextInputFormat
location: class WordCount
WordCount.java:34: error: cannot find symbol
job.setOutputFormatClass(TextOutputFormat.class);
^
symbol: class TextOutputFormat
location: class WordCount
WordCount.java:35: error: cannot find symbol
job.setMapOutputKeyClass(Text.class);
^
symbol: class Text
location: class WordCount
WordCount.java:36: error: cannot find symbol
job.setMapOutputValueClass(IntWritable.class);
^
symbol: class IntWritable
location: class WordCount
WordCount.java:37: error: cannot find symbol
job.setOutputKeyClass(Text.class);
^
symbol: class Text
location: class WordCount
WordCount.java:38: error: cannot find symbol
job.setOutputValueClass(IntWritable.class);
^
symbol: class IntWritable
location: class WordCount
WordCount.java:48: error: cannot find symbol
private final static IntWritable one = new IntWritable(1);
^
symbol: class IntWritable
location: class Map
WordCount.java:49: error: cannot find symbol
private Text word = new Text();
^
symbol: class Text
location: class Map
WordCount.java:51: error: method does not override or implement a method from a supertype
@Override
^
WordCount.java:68: error: cannot find symbol
for (IntWritable value : values) {
^
symbol: class IntWritable
location: class Reduce
WordCount.java:72: error: cannot find symbol
context.write(key, new IntWritable(sum));
^
symbol: class IntWritable
location: class Reduce
WordCount.java:65: error: method does not override or implement a method from a supertype
@Override
^
52 errors
有人可以指出我正确的方向吗？谢谢。
最佳答案
您可以按照以下方式运行它:
javac WordCount.java -cp $(hadoop classpath)
您可以尝试找到
hadoop的确切位置，如下所示对我有用，就像我使用brew在Mac中安装的(在Linux中会有所不同):javac WordCount.java -cp $(/usr/local/Cellar/hadoop/2.8.0/bin/hadoop classpath)
WordCount.class出现在目录中。