前置环境

HDFS环境搭建完成
YARN环境搭建完成

Java开发环境搭建

IDEA创建maven工程

image.png

pom.xml依赖引入

注意hadoop版本对应

  1. <!-- hadoop-client -->
  2. <dependency>
  3.     <groupId>org.apache.hadoop</groupId>
  4.     <artifactId>hadoop-client</artifactId>
  5.     <version>3.2.2</version>
  6. </dependency>

resources引入*site.xml

将/opt/bigdata/hadoop/ect/hadoop/下四个文件拷贝至项目
core-site.xml
hdfs-site.xml
mapred-site.xml
yarn-site.xml

Java编码三个类

MyWordCount

public class MyWordCount {

    public static void main(String[] args) throws Exception {
        // 定义配置
        Configuration conf = new Configuration(true);
        // 定义JOB
        Job job = Job.getInstance(conf);

        job.setJarByClass(MyWordCount.class);
        job.setJobName("myJob");
        // 定义输入输出目录
        Path inFile = new Path("/user/god/input");
        TextInputFormat.addInputPath(job, inFile);
        // /user/god/output必须不能存在，否则创建失败
        Path outFile = new Path("/user/god/output");
        if (outFile.getFileSystem(conf).exists(outFile)) {
            outFile.getFileSystem(conf).delete(outFile, true);
        }
        TextOutputFormat.setOutputPath(job, outFile);
        // 设置map阶段处理
        job.setMapperClass(MyMapper.class);
        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(IntWritable.class);
        // 设置reduce阶段处理
        job.setReducerClass(MyReducer.class);
        // Submit the job, then poll for progress until the job is complete
        job.waitForCompletion(true);
    }
}

�MyMapper

public class MyMapper extends Mapper<Object, Text, Text, IntWritable> {

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

    @Override
    public void map(Object key, Text value, Context context) throws IOException, InterruptedException {
        StringTokenizer itr = new StringTokenizer(value.toString());
        while (itr.hasMoreTokens()) {
            word.set(itr.nextToken());
            context.write(word, one);
        }
    }
}

�MyReducer

public class MyReducer extends Reducer<Text, IntWritable, Text, IntWritable> {
    private IntWritable result = new IntWritable();

    @Override
    public void reduce(Text key, Iterable<IntWritable> values, Context context)
            throws IOException, InterruptedException {
        int sum = 0;
        for (IntWritable val : values) {
            sum += val.get();
        }
        result.set(sum);
        context.write(key, result);
    }
}

�构建打包上传

  • mvn clean package -Dmaven.test.skip=true
  • 将文件course-learn-hadoop.jar上传到主节点服务器
  • 执行命令hadoop jar course-learn-hadoop.jar com.course.learn.hadoop.MyWordCount
  • hdfs dfs -ls /user/god/output

  • hdfs dfs -cat /user/god/output/part-r-00000

    作业提交方式

    开发打包上传执行hadoop命令

    开发 -> jar -> 上传到集群中任意一个节点 -> hadoop jar xxx.jar ooxx in out

    嵌入linux/Windows集群方式

    设置mapreduce.framework.name = yarn
    System.setProperty(“HADOOP_USER_NAME”, “root”);
    conf.set(“mapreduce.app-submission.cross-platform”,”true”)
    job.setJar(“Target目录下jar路径”);

    local单机方式（自测）

    设置mapreduce.framework.name = local
    windows系统必配：

  • conf.set(“mapreduce.app-submission.cross-platform”,”true”);

  • 部署hadoop-3.2.2并且配置HADOOP_HOME环境变量

  • 将部署的hadoop/bin目录下的hadoop.dll复制到c:/windows/system32/下

    参数个性化配置

    public class MyWordCount {

  public static void main(String[] args) throws Exception {
      System.setProperty("HADOOP_USER_NAME", "god");
      // 定义配置
      Configuration conf = new Configuration(true);
      // 个性化参数
      GenericOptionsParser parser = new GenericOptionsParser(conf, args);
      String[] params = parser.getRemainingArgs();
      // 定义JOB
      Job job = Job.getInstance(conf);

      job.setJarByClass(MyWordCount.class);
      job.setJobName("myJob");
      job.setJar(
              "/Users/qinlei/Documents/WorkSpace/IdeaProjects/course/course-learn/course-learn-hadoop/target/course-learn-hadoop.jar");
      // 定义输入输出目录
      Path inFile = new Path(params[0]);
      TextInputFormat.addInputPath(job, inFile);
      // /user/god/output必须不能存在，否则创建失败
      Path outFile = new Path(params[1]);
      if (outFile.getFileSystem(conf).exists(outFile)) {
          outFile.getFileSystem(conf).delete(outFile, true);
      }
      TextOutputFormat.setOutputPath(job, outFile);
      // 设置map阶段处理
      job.setMapperClass(MyMapper.class);
      job.setMapOutputKeyClass(Text.class);
      job.setMapOutputValueClass(IntWritable.class);
      // 设置reduce阶段处理
      job.setReducerClass(MyReducer.class);
      // Submit the job, then poll for progress until the job is complete
      job.waitForCompletion(true);
  }
}

    �设置动态参数，可设置-D mapreduce.job.reduce=2
    image.png