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尚硅谷Hadoop的WordCount案例实操练习出现的bug-环球新视野

来源：博客园


(资料图片仅供参考)

报错日志和exception如下：

点击查看代码
SLF4J: Class path contains multiple SLF4J bindings.SLF4J: Found binding in [jar:file:/D:/Environment/RepMaven/org/slf4j/slf4j-reload4j/1.7.36/slf4j-reload4j-1.7.36.jar!/org/slf4j/impl/StaticLoggerBinder.class]SLF4J: Found binding in [jar:file:/D:/Environment/RepMaven/org/slf4j/slf4j-log4j12/1.7.30/slf4j-log4j12-1.7.30.jar!/org/slf4j/impl/StaticLoggerBinder.class]SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.SLF4J: Actual binding is of type [org.slf4j.impl.Reload4jLoggerFactory]2023-05-26 13:55:26,083 WARN [org.apache.hadoop.util.NativeCodeLoader] - Unable to load native-hadoop library for your platform... using builtin-java classes where applicable  2023-05-26 13:55:26,580 WARN [org.apache.hadoop.metrics2.impl.MetricsConfig] - Cannot locate configuration: tried hadoop-metrics2-jobtracker.properties,hadoop-metrics2.properties  2023-05-26 13:55:26,783 INFO [org.apache.hadoop.metrics2.impl.MetricsSystemImpl] - Scheduled Metric snapshot period at 10 second(s).  2023-05-26 13:55:26,783 INFO [org.apache.hadoop.metrics2.impl.MetricsSystemImpl] - JobTracker metrics system started  2023-05-26 13:55:27,228 WARN [org.apache.hadoop.mapreduce.JobResourceUploader] - Hadoop command-line option parsing not performed. Implement the Tool interface and execute your application with ToolRunner to remedy this.  2023-05-26 13:55:27,351 WARN [org.apache.hadoop.mapreduce.JobResourceUploader] - No job jar file set.  User classes may not be found. See Job or Job#setJar(String).  2023-05-26 13:55:27,383 INFO [org.apache.hadoop.mapreduce.JobSubmitter] - Cleaning up the staging area file:/tmp/hadoop/mapred/staging/yeqiu523558444/.staging/job_local523558444_0001  Exception in thread "main" java.lang.UnsatisfiedLinkError: "boolean org.apache.hadoop.io.nativeio.NativeIO$Windows.access0(java.lang.String, int)"at org.apache.hadoop.io.nativeio.NativeIO$Windows.access0(Native Method)at org.apache.hadoop.io.nativeio.NativeIO$Windows.access(NativeIO.java:793)at org.apache.hadoop.fs.FileUtil.canRead(FileUtil.java:1249)at org.apache.hadoop.fs.FileUtil.list(FileUtil.java:1454)at org.apache.hadoop.fs.RawLocalFileSystem.listStatus(RawLocalFileSystem.java:601)at org.apache.hadoop.fs.FileSystem.listStatus(FileSystem.java:1972)at org.apache.hadoop.fs.FileSystem.listStatus(FileSystem.java:2014)at org.apache.hadoop.fs.FileSystem$4.(FileSystem.java:2180)at org.apache.hadoop.fs.FileSystem.listLocatedStatus(FileSystem.java:2179)at org.apache.hadoop.fs.ChecksumFileSystem.listLocatedStatus(ChecksumFileSystem.java:783)at org.apache.hadoop.mapreduce.lib.input.FileInputFormat.singleThreadedListStatus(FileInputFormat.java:320)at org.apache.hadoop.mapreduce.lib.input.FileInputFormat.listStatus(FileInputFormat.java:279)at org.apache.hadoop.mapreduce.lib.input.FileInputFormat.getSplits(FileInputFormat.java:404)at org.apache.hadoop.mapreduce.JobSubmitter.writeNewSplits(JobSubmitter.java:310)at org.apache.hadoop.mapreduce.JobSubmitter.writeSplits(JobSubmitter.java:327)at org.apache.hadoop.mapreduce.JobSubmitter.submitJobInternal(JobSubmitter.java:200)at org.apache.hadoop.mapreduce.Job$11.run(Job.java:1571)at org.apache.hadoop.mapreduce.Job$11.run(Job.java:1568)at java.base/java.security.AccessController.doPrivileged(AccessController.java:712)at java.base/javax.security.auth.Subject.doAs(Subject.java:439)at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1878)at org.apache.hadoop.mapreduce.Job.submit(Job.java:1568)at org.apache.hadoop.mapreduce.Job.waitForCompletion(Job.java:1589)at com.atgui.mapreduce.wordcount.WordCountDriver.main(WordCountDriver.java:47)
pom.xml环境依赖如下：
点击查看代码
                    org.apache.hadoop            hadoop-client            3.3.4                            junit            junit            4.12                            org.slf4j            slf4j-log4j12            1.7.30
WordCountMapper.java
点击查看代码
package com.atgui.mapreduce.wordcount;import org.apache.hadoop.io.IntWritable;import org.apache.hadoop.io.LongWritable;import org.apache.hadoop.io.Text;import org.apache.hadoop.mapreduce.Mapper;import java.io.IOException;public class WordCountMapper extends Mapper {    private  Text outK = new Text();    private  IntWritable outV = new IntWritable(1);    @Override    protected void map(LongWritable key, Text value,Context context) throws IOException, InterruptedException {        // 1 获取一行        // atguigu atguigu        String line = value.toString();        // 2 切割        // atguigu        // atguigu        String[] words = line.split(" ");        // 3 循环写出        for (String word : words) {            // 封装outK            outK.set(word);            // 写出            context.write(outK, outV);        }    }}
WordCountReduce.java
点击查看代码
package com.atgui.mapreduce.wordcount;import org.apache.hadoop.io.IntWritable;import org.apache.hadoop.mapreduce.Reducer;import org.w3c.dom.Text;import java.io.IOException;public class WordCountReducer extends Reducer {    private IntWritable outV = new IntWritable();    @Override    protected void reduce(Text key, Iterable values, Reducer.Context context) throws IOException, InterruptedException {        int sum = 0;        // atguigu,(1,1)        for (IntWritable value : values) {            sum += value.get();        }        outV.set(sum);        // 写出        context.write(key, outV);    }}
WordCountDriver
点击查看代码
package com.atgui.mapreduce.wordcount;import org.apache.hadoop.conf.Configuration;import org.apache.hadoop.fs.Path;import org.apache.hadoop.io.IntWritable;import org.apache.hadoop.io.Text;import org.apache.hadoop.mapreduce.Job;import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;import java.io.IOException;public class WordCountDriver {//    static {//        try {//            System.load("D:\\Environment\\hadoop-3.1.0\\bin\\hadoop.dll");//        } catch (UnsatisfiedLinkError e) {//            System.err.println("Native code library failed to load.\n" + e);//            System.exit(1);//        }//    }    public static void main(String[] args) throws IOException, InterruptedException, ClassNotFoundException {        // 1 获取job        Configuration conf = new Configuration();        Job job = Job.getInstance(conf);        // 2 设置jar包路径        job.setJarByClass(WordCountDriver.class);        // 3 关联mapper和reducer        job.setMapperClass(WordCountMapper.class);        job.setReducerClass(WordCountReducer.class);        // 4 设置map输出的kv类型        job.setMapOutputKeyClass(Text.class);        job.setMapOutputValueClass(IntWritable.class);        // 5 设置最终输出的kv类型        job.setOutputKeyClass(Text.class);        job.setOutputValueClass(IntWritable.class);        // 6 设置输入路径和输出路径        FileInputFormat.setInputPaths(job,new Path("D:\\Environment\\input\\inputword"));        FileOutputFormat.setOutputPath(job,new Path("D:\\Environment\\hadoop\\output1"));        // 7 提交job        boolean result = job.waitForCompletion(true);        System.exit(result? 0 : 1);    }}
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询问Claude，回答如下：

这个错误是由于WordCount程序在Windows系统上运行时,尝试调用了Hadoop的NativeIO类的access0方法,但无法找到正确的JNI库导致的UnsatisfiedLinkError异常。NativeIO类是Hadoop用来执行一些本地文件操作的类,它依赖于JNI来调用Windows的API。在Windows上运行Hadoop程序时,需要从Hadoop发行包中copy出对应的winutils.exe和hadoop.dll两个文件,并设置相关环境变量,Hadoop程序才能正确加载这两个文件,执行本地文件操作。  所以,导致这个错误的原因是:

  1. 没有从Hadoop发行包中获取winutils.exe和hadoop.dll两个文件。

  2. 获取了这两个文件,但环境变量设置不正确,Hadoop无法加载它们。

    解决方案：在你的driver类中加下面代码，如果可以执行就说明是hadoop.dll的问题

static {        try {            System.load("D:\\Environment\\hadoop-3.1.0\\bin\\hadoop.dll");        } catch (UnsatisfiedLinkError e) {            System.err.println("Native code library failed to load.\n" + e);            System.exit(1);        }    }

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