Hadoop之HDFS中的Java API操作
阿新 • • 發佈:2020-12-18
技術標籤:HadoopJavahadoophdfsjavaapi
API使用
一、準備工作
1.1、解壓
解壓 hadoop 安裝包到非中文路徑(例如:D:\users\hadoop-2.6.0-cdh5.14.2)
1.2、環境變數
在 windows 上配置 HADOOP_HOME 環境變數(與 windows 配置 jdk 環境變數
方法類似)
1.3、新建工程
使用開發工具建立一個 Maven 工程
1.4、依賴包
匯入相應的依賴,依賴如下:
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>RELEASE</version>
</dependency>
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-core</artifactId>
<version>2.8.2</version>
</dependency>
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-common</artifactId>
<version>2.6.0-cdh5.14.2</version>
</dependency>
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-client</artifactId>
<version>2.6.0-cdh5.14.2</version>
</dependency>
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-hdfs</artifactId>
<version>2.6.0-cdh5.14.2</version>
</dependency>
</dependencies>
注意:Maven 倉庫沒有支援 cdh 相關依賴,cloudera 自己建立了一個相關的
倉庫,需要在 pom 單獨新增 cloudera 倉庫。
<repositories>
<repository>
<id>cloudera</id>
<url>https://repository.cloudera.com/artifactory/cloudera-repos/</url>
</repository>
</repositories>
1.5、測試
建立一個包cn.big.data,建立 HdfsClient 類,使用 Junit 方式測試
建立一個目錄
package cn.big.data;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.junit.Test;
import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;
public class HdfsClient {
@Test
public void testMkdirs() throws IOException, InterruptedException, URISyntaxException {
// 1 獲取檔案系統
Configuration conf = new Configuration();
FileSystem fs = FileSystem.get(new URI("hdfs://192.168.247.130:9000"), conf, "root");
// 2 建立目錄
fs.mkdirs(new Path("/myApi"));
// 3 關閉資源
fs.close();
}
}
1.6、注意事項
如果 idea 打印不出日誌,在控制檯上只顯示如下資訊
1.log4j:WARNNoappenderscouldbefoundforlogger(org.apache.hadoop.
util.Shell).
2.log4j:WARNPleaseinitializethelog4jsystemproperly.
3.log4j:WARNSeehttp://logging.apache.org/log4j/1.2/faq.html#noconfi
gformoreinfo.
需要在專案的 src/main/resources 目錄下,新建一個檔案,命名為
“log4j.properties”,在檔案中填入:
log4j.rootLogger=INFO, 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
log4j.appender.logfile=org.apache.log4j.FileAppender
log4j.appender.logfile.File=target/spring.log
log4j.appender.logfile.layout=org.apache.log4j.PatternLayout
log4j.appender.logfile.layout.ConversionPattern=%d %p [%c] - %m%n
二、使用方法
2.1、HDFS 檔案上傳
@Test
public void upLoad() throws URISyntaxException, IOException, InterruptedException {
Configuration configuration = new Configuration();
// 設定副本儲存數量為1,預設是3
configuration.set("dfs.replication","1");
FileSystem fs = FileSystem.get(new URI("hdfs://192.168.247.130:9000"),configuration,"root");
//上傳檔案
fs.copyFromLocalFile(new Path("D:\\study\\codes\\hadoop\\HdfsClientDemo\\data\\hdfsDemo\\test.txt"),new Path("/myApi/"));
//關閉資源
fs.close();
System.out.println("ok");
}
2.2、HDFS 檔案下載
@Test
public void downLoad() throws URISyntaxException, IOException, InterruptedException {
Configuration configuration = new Configuration();
FileSystem fs = FileSystem.get(new URI("hdfs://192.168.247.130:9000"),configuration,"root");
//下載檔案
// boolean delSrc 指是否將原檔案刪除
// Path src 指要下載的檔案路徑
// Path dst 指將檔案下載到的路徑
// boolean useRawLocalFileSystem 是否開啟檔案校驗
fs.copyToLocalFile(false,new Path("/myApi/test.txt"),new Path("D:\\study\\codes\\hadoop\\HdfsClientDemo\\HdfsTest"),true);
fs.close();
}
2.3、HDFS 資料夾刪除
@Test
public void dRemove() throws URISyntaxException, IOException, InterruptedException {
Configuration configuration = new Configuration();
FileSystem fs = FileSystem.get(new URI("hdfs://192.168.247.130:9000"),configuration,"root");
//刪除資料夾
fs.delete(new Path("/myApi/remove"),true);
fs.close();
}
2.4、HDFS 檔名更改
public void fRename() throws URISyntaxException, IOException, InterruptedException {
Configuration configuration = new Configuration();
FileSystem fs = FileSystem.get(new URI("hdfs://192.168.247.130:9000"),configuration,"root");
//修改檔名
fs.rename(new Path("/myApi/test.txt"),new Path("/myApi/testRename.txt"));
fs.close();
}
2.5、HDFS 檔案詳情檢視
@Test
public void testListFiles() throws IOException, URISyntaxException, InterruptedException {
Configuration configuration = new Configuration();
FileSystem fs = FileSystem.get(new URI("hdfs://192.168.247.130:9000"),configuration,"root");
//獲取檔案詳情
RemoteIterator<LocatedFileStatus> listFiles = fs.listFiles(new Path("/"),true);
while (listFiles.hasNext()){
LocatedFileStatus status = listFiles.next();
//輸出詳情
//檔名稱
System.out.println(status.getPath().getName());
//長度
System.out.println(status.getLen());
//許可權
System.out.println(status.getPermission());
//組
System.out.println(status.getGroup());
//獲取儲存的塊資訊
BlockLocation[] blockLocations = status.getBlockLocations();
for (BlockLocation blockLocation : blockLocations) {
//獲取塊儲存的主機節點
String[] hosts = blockLocation.getHosts();
for (String host : hosts) {
System.out.println(host);
}
}
System.out.println("-------------------------------");
}
}
2.6、HDFS 檔案和資料夾判斷
@Test
public void testListStatus() throws URISyntaxException, IOException, InterruptedException {
Configuration configuration = new Configuration();
FileSystem fs = FileSystem.get(new URI("hdfs://192.168.247.130:9000"),configuration,"root");
//判斷是檔案還是資料夾
FileStatus[] listStatus = fs.listStatus(new Path("/"));
for (FileStatus fileStatus : listStatus) {
if (fileStatus.isFile()){
System.out.println("f:"+fileStatus.getPath().getName());
}else {
System.out.println("d:"+fileStatus.getPath().getName());
}
}
fs.close();
}
2.7、HDFS 的 I/O 流操作
2.7.1 檔案上傳
@Test
public void putFileToHDFS() throws URISyntaxException, IOException, InterruptedException {
Configuration configuration = new Configuration();
FileSystem fs = FileSystem.get(new URI("hdfs://192.168.247.130:9000"),configuration,"root");
//建立輸入流
FileInputStream fis = new FileInputStream(new File("D:\\study\\codes\\hadoop\\HdfsClientDemo\\HdfsTest\\test.txt"));
//獲取輸出流
FSDataOutputStream fos = fs.create(new Path("/myApi/testIO.txt"));
//執行流拷貝
IOUtils.copyBytes(fis,fos,configuration);
//關閉資源
IOUtils.closeStream(fis);
IOUtils.closeStream(fos);
}
2.7.2 檔案下載
@Test
public void getFileFromHDFS() throws URISyntaxException, IOException, InterruptedException {
Configuration configuration = new Configuration();
FileSystem fs = FileSystem.get(new URI("hdfs://192.168.247.130:9000"),configuration,"root");
//獲取輸入流
FSDataInputStream fis = fs.open(new Path("/myApi/testIO.txt"));
//獲取輸出流
FileOutputStream fos = new FileOutputStream(new File("D:\\study\\codes\\hadoop\\HdfsClientDemo\\HdfsTest\\IODownload.txt"));
//流的對拷
IOUtils.copyBytes(fis,fos,configuration);
//關閉資源
IOUtils.closeStream(fis);
IOUtils.closeStream(fos);
fs.close();
}
2.8、定位檔案讀取
這裡強調可以設定任意位置讀取 hdfs 檔案,對於 mapreduce 分片 inputsplit 和 spark 分割槽理解有一定幫助。
先將 hadoop 安裝包上傳到 HDFS 檔案系統
下載第一塊
@Test
public void readFileSeek1() throws URISyntaxException, IOException, InterruptedException {
Configuration configuration = new Configuration();
FileSystem fs = FileSystem.get(new URI("hdfs://192.168.247.130:9000"),configuration,"root");
FSDataInputStream fis = fs.open(new Path("/myApi//hadoop-2.6.0-cdh5.14.2.tar.gz"));
FileOutputStream fos = new FileOutputStream(new File("C:\\Users\\Dongue\\Desktop\\seek\\hadoop-2.6.0-cdh5.14.2.tar.gz.part1"));
//流的拷貝
byte[] buf = new byte[1024];
for (int i = 0; i < 1024 * 128; i++) {
fis.read(buf);
fos.write(buf);
}
IOUtils.closeStream(fis);
IOUtils.closeStream(fos);
}
下載成功
下載第二塊
@Test
public void readFileSeek2() throws URISyntaxException, IOException, InterruptedException {
Configuration configuration = new Configuration();
FileSystem fs = FileSystem.get(new URI("hdfs://192.168.247.130:9000"),configuration,"root");
FSDataInputStream fis = fs.open(new Path("/myApi//hadoop-2.6.0-cdh5.14.2.tar.gz"));
//定位輸入資料位置
fis.seek(1024*1024*128);
FileOutputStream fos = new FileOutputStream(new File("C:\\Users\\Dongue\\Desktop\\seek\\hadoop-2.6.0-cdh5.14.2.tar.gz.part2"));
//流的對拷
IOUtils.copyBytes(fis,fos,configuration);
IOUtils.closeStream(fis);
IOUtils.closeStream(fos);
}
合併檔案
在 window 命令視窗中執行
type hadoop-2.6.0-cdh5.14.2.tar.gz.part2 >> hadoop-2.6.0-cdh5.14.2.tar.gz.part1
合併後就是完整的 hadoop 安裝包檔案