如何在 Hortonworks Sandbox 中编译 WordCount.java？

Question

我正在学习教程并尝试 运行 Hortonworks Data Platform Sandbox 中的 WordCount 示例。但是，当我尝试从命令行编译时出现错误并且无法构建它。

在终端我输入Java编译命令：

$ javac WordCount.java

我没有编译和获取 .class 文件，而是收到以下错误：

WordCount.java:27: error: package org.apache.hadoop.conf does not exist

import org.apache.hadoop.conf.Configuration;

^

WordCount.java:28: error: package org.apache.hadoop.conf does not exist

import org.apache.hadoop.conf.Configured;

^

WordCount.java:29: error: package org.apache.hadoop.fs does not exist

import org.apache.hadoop.fs.Path;

^

WordCount.java:30: error: package org.apache.hadoop.io does not exist

import org.apache.hadoop.io.IntWritable;

^

WordCount.java:31: error: package org.apache.hadoop.io does not exist

import org.apache.hadoop.io.LongWritable;

^

WordCount.java:32: error: package org.apache.hadoop.io does not exist

import org.apache.hadoop.io.Text;

^

WordCount.java:42: error: package org.apache.hadoop.util does not exist

import org.apache.hadoop.util.Tool;

^

WordCount.java:43: error: package org.apache.hadoop.util does not exist

import org.apache.hadoop.util.ToolRunner;

^

WordCount.java:54: error: cannot find symbol

public class WordCount extends Configured implements Tool {

^

symbol: class Configured

WordCount.java:54: error: cannot find symbol

public class WordCount extends Configured implements Tool {

^

symbol: class Tool

WordCount.java:61: error: cannot access Closeable

public static class MapClass extends MapReduceBase

^

class file for org.apache.hadoop.io.Closeable not found

WordCount.java:64: error: cannot find symbol

private final static IntWritable one = new IntWritable(1);

^

symbol: class IntWritable

location: class MapClass

WordCount.java:65: error: cannot find symbol

private Text word = new Text();

^

symbol: class Text

location: class MapClass

WordCount.java:67: error: cannot find symbol

public void map(LongWritable key, Text value,

^

symbol: class LongWritable

location: class MapClass

WordCount.java:67: error: cannot find symbol

public void map(LongWritable key, Text value,

^

symbol: class Text

location: class MapClass

WordCount.java:68: error: cannot find symbol

OutputCollector<Text, IntWritable> output,

^

symbol: class Text

location: class MapClass

WordCount.java:68: error: cannot find symbol

OutputCollector<Text, IntWritable> output,

^

symbol: class IntWritable

location: class MapClass

WordCount.java:83: error: cannot find symbol

implements Reducer<Text, IntWritable, Text, IntWritable> {

^

symbol: class Text

location: class WordCount

WordCount.java:83: error: cannot find symbol

implements Reducer<Text, IntWritable, Text, IntWritable> {

^

symbol: class IntWritable

location: class WordCount

WordCount.java:83: error: cannot find symbol

implements Reducer<Text, IntWritable, Text, IntWritable> {

^

symbol: class Text

location: class WordCount

WordCount.java:83: error: cannot find symbol

implements Reducer<Text, IntWritable, Text, IntWritable> {

^

symbol: class IntWritable

location: class WordCount

WordCount.java:85: error: cannot find symbol

public void reduce(Text key, Iterator<IntWritable> values,

^

symbol: class Text

location: class Reduce

WordCount.java:85: error: cannot find symbol

public void reduce(Text key, Iterator<IntWritable> values,

^

symbol: class IntWritable

location: class Reduce

WordCount.java:86: error: cannot find symbol

OutputCollector<Text, IntWritable> output,

^

symbol: class Text

location: class Reduce

WordCount.java:86: error: cannot find symbol

OutputCollector<Text, IntWritable> output,

^

symbol: class IntWritable

location: class Reduce

我做错了什么？我使用当前版本的 Hortonworks Sandbox 2.6.1。 Hadoop 版本为 3.1.1

Answer 1

您需要指定正确的 class 路径。在 Sandbox 中你可以使用 hadoop class路径信息。

试试这个（注意引号，它们必须是反引号！"`"）：

$ javac -cp `hadoop classpath` WordCount.java