Java变量

Question

我是新手编译Hadoop代码并且知道这个问题已被多次回答。但是，我仍然发现很难找出正确的类路径来使WordCount.java代码进行编译。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

当我回复$ PATH时，我得到了以下内容：

/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:/usr/lib/jvm/jre-1.7.0-openjdk /：/ USR /本地/ Hadoop的/ bin中：在/ usr /本地/ Hadoop的/ sbin目录：/home/hduser/.local/bin：/家庭/ hduser /斌：/usr/lib/jvm/jre-1.7.0-openjdk/：的/ usr /本地/ hadoop的/ bin中：在/ usr /本地/ hadoop的/ sbin目录

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中为Java和Hadoop设置了所有环境变量，如下所示，并且jps通过。 Java也可以编译其他代码，但我认为我得到了Hadoop的类路径错误。

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，我收到了这些错误：

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

有人能指出我正确的方向吗？谢谢。

Answer 1

您可以像下面这样运行它：

javac WordCount.java -cp $(hadoop classpath)

如果您收到以下错误：

zsh：找不到命令：hadoop

javac：-cp需要一个参数

您可以尝试找到hadoop的确切位置，因为以下对我有效，因为我使用brew在Mac中安装（在Linux中会有所不同）：

javac WordCount.java -cp $(/usr/local/Cellar/hadoop/2.8.0/bin/hadoop classpath)

hadoop类路径为编译器提供了正确编译所需的所有路径，您应该会在目录中看到生成的WordCount.class。

Answer 2

我也有Hadoop 2.7.1，我可以编译WordCount。

所有丢失的软件包均来自hadoop-common和hadoop-core个罐子。

你需要在你的pom.xml中包含以下Maven依赖项（我只有以下依赖项并且它为我编译）：

<dependencies>
    <dependency>
        <groupId>org.apache.hadoop</groupId>
        <artifactId>hadoop-hdfs</artifactId>
        <version>2.7.1</version>
    </dependency>

    <dependency>
        <groupId>org.apache.hadoop</groupId>
        <artifactId>hadoop-common</artifactId>
        <version>2.7.1</version>
    </dependency>

    <dependency>
        <groupId>org.apache.hadoop</groupId>
        <artifactId>hadoop-core</artifactId>
        <version>1.2.1</version>
    </dependency>
</dependencies>

包org.apache.hadoop.conf不存在

Java变量

Hadoop变量

2 个答案: