hadoop3.x：Sequence File序列化文件-写文件-马育民老师

# 创建maven工程

略

[idea创建maven工程必须修改idea配置](https://www.malaoshi.top/show_1IXSDwcJyst.html "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);
		}
	}
	
}

```

原文出处：http://malaoshi.top/show_1IX2AIA6dLbk.html