创建maven工程

略

idea创建maven工程必须修改idea配置

pom.xml

<dependencies>
    <dependency>
        <groupId>org.apache.hadoop</groupId>
        <artifactId>hadoop-common</artifactId>
        <version>3.0.3</version>
    </dependency>
    <dependency>
        <groupId>org.apache.hadoop</groupId>
        <artifactId>hadoop-hdfs</artifactId>
        <version>3.0.3</version>
    </dependency>
    <dependency>
        <groupId>org.apache.hadoop</groupId>
        <artifactId>hadoop-client</artifactId>
        <version>3.0.3</version>
    </dependency>
</dependencies>

在 pom.xml 点击右键 -> 【maven】 -> 【reimport】 导入依赖

log4j.properties

打印 hadoop debug 信息

在 resources 文件夹下创建 log4j.properties 文件，内容如下：

log4j.rootLogger=DEBUG, stdout
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%d %p [%c] - %m%n

java

package top.malaoshi;
import java.io.File;
import java.util.List;
import org.apache.commons.io.FileUtils;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IOUtils;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.SequenceFile;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.compress.CompressionCodec;
import org.apache.hadoop.io.compress.GzipCodec;
public class Write {    
    public static void main(String[] args) throws Exception {
        File file=new File("C:/Users/mym/Desktop/4.txt");
        List<String> list=FileUtils.readLines(file);
        // 设置客户端运行身份 以root去操作访问HDFS
        System.setProperty("HADOOP_USER_NAME", "root");
        // Configuration 用于指定相关参数属性
        Configuration conf = new Configuration();
        // sequence file key、value
        IntWritable key = new IntWritable();
        Text value = new Text();
        // 构造Writer参数属性
        SequenceFile.Writer writer = null;
        //使用 gzip 构建压缩编码器
        CompressionCodec gzip = new GzipCodec();
        /*
         * 文件保存路径
         * namenode端口号
         * 文件名后面加上压缩格式的后缀
         */
        Path path=new Path("hdfs://hadoop1:8020/"+file.getName()+gzip.getDefaultExtension());
        SequenceFile.Writer.Option optPath = SequenceFile.Writer.file(path);
        //指定key的class
        SequenceFile.Writer.Option optKey = SequenceFile.Writer.keyClass(key.getClass());
        //指定value的class
        SequenceFile.Writer.Option optVal = SequenceFile.Writer.valueClass(value.getClass());
        /*
         * 指定压缩类型：record（或block）
         * 指定压缩编码器：gzip
         */
        SequenceFile.Writer.Option optCom = SequenceFile.Writer.compression(SequenceFile.CompressionType.RECORD, gzip);
        try {
            writer = SequenceFile.createWriter(conf, optPath, optKey, optVal, optCom);
            for (int i = 0,len=list.size(); i < len; i++) {
                key.set(i);
                value.set(list.get(i));
                System.out.println(key+"==="+value);
                writer.append(key, value);
            }
        }catch(Exception e){
            e.printStackTrace();
        } finally {
            IOUtils.closeStream(writer);
        }
    }
}