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一、WordCount代码

(一)WordCount简介

1.wordcount.txt

(二)WordCount的java代码

1.WordCountMapper

2.WordCountReduce

3.WordCountDriver

(三)IDEA运行结果

(四)Hadoop运行wordcount

1.在HDFS上新建一个文件目录

2.新建一个文件，并上传至该目录下

3.执行wordcount命令

4.查看运行结果

5.第二次提交报错原因

6.进入NodeManager查看

7.启动历史服务器(如果已经启动可以忽略此步骤)

8.查看历史服务信息

三、执行本地代码

(一)项目代码

1.stuscore.csv

2.Student类

2.StudentMapper类

4.StudentReduce类

5.StudentDriver类

(二)java代码中指定路径

1.maven项目编译并打包

2.上传stuscore.csv到hdfs指定目录下

3.xftp上传target目录下的打包好的jar包上传到虚拟机

4.Hadoop运行hadoopstu-1.0-SNAPSHOT.jar

5.Hadoop运行结果

(三)java代码中不指定路径

1.StuudentDriver类

2.重新编译打包上传

3.HDFS命令执行该jar包

4.查看运行结果

一、WordCount代码

(一)WordCount简介

WordCount是大数据经典案例，其逻辑就是有一个文本文件，通过编写java代码与Hadoop核心组件的操作，查询每个单词出现的频率。

1.wordcount.txt

hello java
hello hadoop
hello java hadoop
java hadoop
java hadoop
hadoop java
hello java

(二)WordCount的java代码

1.WordCountMapper

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;

// Mapper<KEYIN, VALUEIN, KEYOUT, VALUEOUT>
//                                         <0,"hello world","hello",1>
public class WordCountMapper extends Mapper<LongWritable, Text,Text, IntWritable> {
    Text text = new Text();
    IntWritable intWritable = new IntWritable();
    @Override
    protected void map(LongWritable key, Text value, Mapper<LongWritable, Text, Text, IntWritable>.Context context) throws IOException, InterruptedException {
        System.out.println("WordCount stage Key:"+key+" Value:"+value);
        String[] words = value.toString().split(" ");// "hello world" -->[hello,world]
        for (String word :
                words) {
            text.set(word);
            intWritable.set(1);
            context.write(text,intWritable);// 输出键值对 <hello,1><world,1>
        }
    }
}

2.WordCountReduce

import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;

import java.io.IOException;

// <KEYIN, VALUEIN, KEYOUT, VALUEOUT>
public class WordCountReduce extends Reducer<Text, IntWritable,Text, LongWritable> {
    @Override
    protected void reduce(Text key, Iterable<IntWritable> values, Reducer<Text, IntWritable, Text, LongWritable>.Context context) throws IOException, InterruptedException {
        System.out.println("Reduce stage Key:"+key+" Values:"+values.toString());
        int count = 0;
        for (IntWritable intWritable :
                values) {
            count += intWritable.get();
        }
//        LongWritable longWritable = new LongWritable();
//        longWritable.set(count);
        LongWritable longWritable = new LongWritable(count);
        System.out.println("Key:"+key+" ResultValue:"+longWritable.get());
        context.write(key,longWritable);
    }
}

3.WordCountDriver

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
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 {
    public static void main(String[] args) throws IOException, InterruptedException, ClassNotFoundException {
        Configuration configuration = new Configuration();
        Job job = Job.getInstance(configuration);

        job.setJarByClass(WordCountDriver.class);

        // 设置mapper类
        job.setMapperClass(WordCountMapper.class);
        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(IntWritable.class);

        // 设置reduce类
        job.setReducerClass(WordCountReduce.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(LongWritable.class);

        // 指定map输入的文件路径
        FileInputFormat
                .setInputPaths(job,new Path("D:\\javaseprojects\\hadoopstu\\input\\demo1\\wordcount.txt"));
        // 指定reduce结果输出的文件路径
        Path path = new Path("D:\\javaseprojects\\hadoopstu\\output");
        FileSystem fileSystem = FileSystem.get(path.toUri(),configuration);

        if(fileSystem.exists(path)){
            fileSystem.delete(path,true);
        }
        FileOutputFormat.setOutputPath(job,path);
        job.waitForCompletion(true);
//        job.setJobName("");
    }
}

(三)IDEA运行结果

Hadoop之——WordCount案例与执行本地jar包

(四)Hadoop运行wordcount

1.在HDFS上新建一个文件目录

[root@lxm147 ~]# hdfs dfs -mkdir /inputpath
2023-02-10 23:05:40,098 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
[root@lxm147 ~]# hdfs dfs -ls /
2023-02-10 23:05:52,217 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
Found 3 items
drwxr-xr-x   - root supergroup          0 2023-02-08 08:06 /aa
drwxr-xr-x   - root supergroup          0 2023-02-10 10:52 /bigdata
drwxr-xr-x   - root supergroup          0 2023-02-10 23:05 /inputpath

2.新建一个文件，并上传至该目录下

[root@lxm147 mapreduce]# vim ./test.csv
[root@lxm147 mapreduce]# hdfs dfs -put ./test.csv /inputpath

Hadoop之——WordCount案例与执行本地jar包

3.执行wordcount命令

[root@lxm147 mapreduce]# hadoop jar ./hadoop-mapreduce-examples-3.1.3.jar wordcount /inputpath /outputpath

4.查看运行结果

(1)web端

Hadoop之——WordCount案例与执行本地jar包

(2)命令行

[root@lxm147 mapreduce]# hdfs dfs -cat /outputpath/part-r-00000
2023-02-10 23:26:06,276 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
2023-02-10 23:26:07,793 INFO sasl.SaslDataTransferClient: SASL encryption trust check: localHostTrusted = false, remoteHostTrusted = false
hadoop	1
hello	2
java	2
javaweb	1
mybatis	2
spring	1

5.第二次提交报错原因

执行wordcount命令前删除/outpath目录下的文件再执行即可

6.进入NodeManager查看

http://lxm147:8088/cluster

Hadoop之——WordCount案例与执行本地jar包

7.启动历史服务器(如果已经启动可以忽略此步骤)

[root@lxm148 ~]# mr-jobhistory-daemon.sh start historyserver
WARNING: Use of this script to start the MR JobHistory daemon is deprecated.
WARNING: Attempting to execute replacement "mapred --daemon start" instead.
[root@lxm148 ~]# jps
4546 SecondaryNameNode
6370 JobHistoryServer
4164 NameNode
4804 ResourceManager
4937 NodeManager
6393 Jps
4302 DataNode

8.查看历史服务信息

http://lxm147:19888/

Hadoop之——WordCount案例与执行本地jar包

三、执行本地代码

(一)项目代码

1.stuscore.csv

1,zs,10,语文
2,ls,98,语文
3,ww,80,语文
1,zs,20,数学
2,ls,87,数学
3,ww,58,数学
1,zs,44,英语
2,ls,66,英语
3,ww,40,英语
1,zs,55,政治
2,ls,60,政治
3,ww,80,政治
1,zs,10,化学
2,ls,28,化学
3,ww,78,化学
1,zs,87,生物
2,ls,9,生物
3,ww,10,生物

2.Student类

import org.apache.hadoop.io.WritableComparable;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;

public class Student implements WritableComparable<Student> {
    private long stuid;
    private String stuname;
    private int score;
    private String lession;

    @Override
    public int compareTo(Student o) {
        return this.score > o.score ? 1 : 0;
    }

    @Override
    public void write(DataOutput dataOutput) throws IOException {
        dataOutput.writeLong(stuid);
        dataOutput.writeUTF(stuname);
        dataOutput.writeUTF(lession);
        dataOutput.writeInt(score);
    }

    @Override
    public void readFields(DataInput dataInput) throws IOException {
        this.stuid = dataInput.readLong();
        this.stuname = dataInput.readUTF();
        this.lession = dataInput.readUTF();
        this.score = dataInput.readInt();
    }

    @Override
    public String toString() {
        return "Student{" +
                "stuid=" + stuid +
                ", stuname='" + stuname + '\'' +
                ", score=" + score +
                ", lession='" + lession + '\'' +
                '}';
    }

    public long getStuid() {
        return stuid;
    }

    public void setStuid(long stuid) {
        this.stuid = stuid;
    }

    public String getStuname() {
        return stuname;
    }

    public void setStuname(String stuname) {
        this.stuname = stuname;
    }

    public int getScore() {
        return score;
    }

    public void setScore(int score) {
        this.score = score;
    }

    public String getLession() {
        return lession;
    }

    public void setLession(String lession) {
        this.lession = lession;
    }

    public Student(long stuid, String stuname, int score, String lession) {
        this.stuid = stuid;
        this.stuname = stuname;
        this.score = score;
        this.lession = lession;
    }

    public Student() {
    }
}

2.StudentMapper类

import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;

import java.io.IOException;

// K=id,V=student
// Mapper<进来的K,进来的V,出去的K,出去的V>
public class StudentMapper extends Mapper<LongWritable, Text, LongWritable, Student> {
    @Override
    protected void map(LongWritable key, Text value, Mapper<LongWritable, Text, LongWritable, Student>.Context context) throws IOException, InterruptedException {
        System.out.println(key+"   "+value.toString());
        String[] split = value.toString().split(",");
        LongWritable stuidKey = new LongWritable(Long.parseLong(split[2]));
        Student studentValue = new Student(Long.parseLong(split[0]), split[1], Integer.parseInt(split[2]),split[3]);
        context.write(stuidKey,studentValue);
    }
}

4.StudentReduce类

import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.mapreduce.Reducer;

import java.io.IOException;

public class StudentReduce extends Reducer<LongWritable, Student, Student, NullWritable> {
    @Override
    protected void reduce(LongWritable key, Iterable<Student> values, Reducer<LongWritable, Student, Student, NullWritable>.Context context) throws IOException,
            InterruptedException {
        Student stu = new Student();
        // 相同key相加
//        int sum = 0;
        int max = 0;
        String name ="";
        String lession = "";
//        for (Student student:
//             values) {
//            sum += student.getScore();
//            name = student.getStuname();
//        }
        // 求每门科目的最高分
        for (Student student :
                values) {
            if(max<=student.getScore()){
                max = student.getScore();
                name = student.getStuname();
                lession = student.getLession();
            }
        }
        stu.setStuid(key.get());
        stu.setScore(max);
        stu.setStuname(name);
        stu.setLession(lession);
        System.out.println(stu.toString());
        context.write(stu,NullWritable.get());
    }
}

5.StudentDriver类

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;
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 StudentDriver {
    public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
        Configuration configuration = new Configuration();
        Job job = Job.getInstance(configuration);

        job.setJarByClass(StudentDriver.class);

        job.setMapperClass(StudentMapper.class);
        job.setMapOutputKeyClass(LongWritable.class);
        job.setMapOutputValueClass(Student.class);

        job.setReducerClass(StudentReduce.class);
        job.setOutputKeyClass(Student.class);
        job.setOutputValueClass(NullWritable.class);

        // 指定路径
        FileInputFormat.setInputPaths(job,
                new Path("hdfs://lxm147:9000/bigdata/in/demo2/stuscore.csv"));
        Path path = new Path("hdfs://lxm147:9000/bigdata/out2");

        // 不指定路径
       /* Path inpath = new Path(args[0]);
        FileInputFormat.setInputPaths(job, inpath);
        Path path = new Path(args[1]);*/

        FileSystem fs = FileSystem.get(path.toUri(), configuration);
        if (fs.exists(path)) {
            fs.delete(path, true);
        }

        FileOutputFormat.setOutputPath(job, path);
        job.waitForCompletion(true);
    }
}

(二)java代码中指定路径

1.maven项目编译并打包

分别双击compile和package

Hadoop之——WordCount案例与执行本地jar包

2.上传stuscore.csv到hdfs指定目录下

hdfs dfs -put /opt/stuscore.csv /bigdata/in/demo2

3.xftp上传target目录下的打包好的jar包上传到虚拟机

Hadoop之——WordCount案例与执行本地jar包

4.Hadoop运行hadoopstu-1.0-SNAPSHOT.jar

[root@lxm147 opt]# hadoop jar ./hadoopstu-1.1.0-SNAPSHOT.jar nj.zb.kb21.demo2.StudentDriver /bigdata/in/demo2/stuscore.csv /bigdata/out2

5.Hadoop运行结果

Hadoop之——WordCount案例与执行本地jar包

(三)java代码中不指定路径

1.StuudentDriver类

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;
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 StudentDriver {
    public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
        Configuration configuration = new Configuration();
        Job job = Job.getInstance(configuration);

        job.setJarByClass(StudentDriver.class);

        job.setMapperClass(StudentMapper.class);
        job.setMapOutputKeyClass(LongWritable.class);
        job.setMapOutputValueClass(Student.class);

        job.setReducerClass(StudentReduce.class);
        job.setOutputKeyClass(Student.class);
        job.setOutputValueClass(NullWritable.class);

        // 指定路径
        /*FileInputFormat.setInputPaths(job,
                new Path("hdfs://lxm147:9000/bigdata/in/demo2/stuscore.csv"));
        Path path = new Path("hdfs://lxm147:9000/bigdata/out2");*/

        // 不指定路径
        Path inpath = new Path(args[0]);
        FileInputFormat.setInputPaths(job, inpath);
        Path path = new Path(args[1]);

        FileSystem fs = FileSystem.get(path.toUri(), configuration);
        if (fs.exists(path)) {
            fs.delete(path, true);
        }

        FileOutputFormat.setOutputPath(job, path);
        job.waitForCompletion(true);
    }
}

2.重新编译打包上传

为了方便区分，这里修改版本号再重新编译打包

Hadoop之——WordCount案例与执行本地jar包文章来源地址https://www.toymoban.com/news/detail-482586.html

3.HDFS命令执行该jar包

[root@lxm147 opt]# hadoop jar ./hadoopstu-1.1.0-SNAPSHOT.jar nj.zb.kb21.demo2.StudentDriver /bigdata/in/demo2/stuscore.csv /bigdata/out

4.查看运行结果

[root@lxm147 opt]# hdfs dfs -cat /bigdata/out/part-r-00000
Student{stuid=1, stuname='zs', score=226}
Student{stuid=2, stuname='ls', score=348}
Student{stuid=3, stuname='ww', score=346}

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