- 在IDEA中创建一个Maven工程teaching
- 导入相应的依赖
junit junit RELEASE org.apache.logging.log4j log4j-core 2.8.2 org.apache.hadoop hadoop-common 2.7.2 org.apache.hadoop hadoop-client 2.7.2 org.apache.hadoop hadoop-hdfs 2.7.2
- 创建包名：com.test.hdfs
- 创建HdfsClient类
package com.test.hdfs;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;
public class HDFSClient {
public static void main(String[] args){
// 1 获取文件系统配置
Configuration configuration = new Configuration();
FileSystem fs = null;
try {
fs = FileSystem.get(new URI("hdfs://10.13.11.22:8020"), configuration,"hdfs");
// 2 创建目录
fs.mkdirs(new Path("/teaching/hdfs2"));
} catch (IOException | InterruptedException | URISyntaxException e) {
e.printStackTrace();
} finally {
if(fs != null){
// 3 关闭资源
try {
fs.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
- 执行程序
客户端去操作hdfs时，设定默认用户：hdfs - 注意：如果打印不出日志，在控制台上只显示
1.log4j:WARN No appenders could be found for logger (org.apache.hadoop.util.Shell). 2.log4j:WARN Please initialize the log4j system properly. 3.log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
需要在项目的src/main/resources目录下，新建一个文件，命名为“log4j.properties”，在文件中填入
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%n3.2 HDFS的文件操作 3.2.1.HDFS文件上传（测试参数优先级）
- 编写源代码
public static void upFile(String filePath, String dstPath){
Configuration configuration = new Configuration();
FileSystem fileSystem = null;
try{
// 设置副本数
configuration.set("dfs.replication","2");
fileSystem = FileSystem.get(new URI("hdfs://10.13.11.22:8020"), configuration, "hdfs");
fileSystem.copyFromLocalFile(new Path(filePath),new Path(dstPath));
} catch(Exception e){
e.printStackTrace();
} finally {
if(fileSystem != null){
try {
fileSystem.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
- 将hdfs-site.xml拷贝到项目的根目录下
dfs.replication 1
- 参数优先级
客户端代码中设置的值 > classpath下的用户自定义配置文件 > 然后是服务器的默认配置（副本数3）
public static void downloadFile(String hdfsFile, String dst){
Configuration configuration = new Configuration();
FileSystem fs = null;
try {
fs = FileSystem.get(new URI("hdfs://10.13.11.22:8020"), configuration, "hdfs");
// boolean delSrc 指是否将原文件删除，默认：false
// Path src 指要下载的文件路径
// Path dst 指将文件下载到的路径
// boolean useRawLocalFileSystem 是否开启文件校验，不开启文件校验，下载时会多一个crc文件，默认：false
fs.copyToLocalFile(false,new Path(hdfsFile), new Path(dst),true);
} catch (IOException | InterruptedException | URISyntaxException e) {
e.printStackTrace();
} finally {
if(fs != null){
try {
fs.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
3.2.3.HDFS文件夹删除
public static void delete(String filePath){
Configuration configuration = new Configuration();
FileSystem fs = null;
try {
fs = FileSystem.get(new URI("hdfs://10.13.11.22:8020"), configuration, "hdfs");
// Path f 删除的路径
// boolean recursive 路径是目录设置为true，路径为文件，可以设置为true或者false
fs.delete(new Path(filePath),true);
} catch (IOException | InterruptedException | URISyntaxException e) {
e.printStackTrace();
} finally {
if(fs != null){
try {
fs.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
3.2.4.HDFS文件名更改
public static void rename(String srcPath, String dstPath) {
Configuration configuration = new Configuration();
FileSystem fs = null;
try {
fs = FileSystem.get(new URI("hdfs://10.13.11.22:8020"), configuration, "hdfs");
fs.rename(new Path(srcPath), new Path(dstPath));
} catch (IOException | InterruptedException | URISyntaxException e) {
e.printStackTrace();
} finally {
if(fs != null){
try {
fs.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
3.2.5.HDFS文件详情查看
查看文件名称、权限、长度、块信息
public static void listFiles(String path){
Configuration configuration = new Configuration();
FileSystem fs = null;
try {
fs = FileSystem.get(new URI("hdfs://10.13.11.22:8020"), configuration, "hdfs");
RemoteIterator files = fs.listFiles(new Path(path),true);
while(files.hasNext()){
LocatedFileStatus locatedFileStatus = files.next();
System.out.println(locatedFileStatus.getPath().getName());
System.out.println(locatedFileStatus.getLen());
System.out.println(locatedFileStatus.getPermission());
System.out.println(locatedFileStatus.getGroup());
BlockLocation[] blockLocations = locatedFileStatus.getBlockLocations();
for(BlockLocation blockLocation: blockLocations){
String[] hosts = blockLocation.getHosts();
for(String host:hosts){
System.out.println(host);
}
}
}
} catch (IOException | InterruptedException | URISyntaxException e) {
e.printStackTrace();
} finally {
if(fs != null){
try {
fs.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
3.2.6.HDFS文件和文件夹判断
public static void fileStatus(String path) {
Configuration configuration = new Configuration();
FileSystem fs = null;
try {
fs = FileSystem.get(new URI("hdfs://10.13.11.22:8020"), configuration, "hdfs");
FileStatus[] fileStatus = fs.listStatus(new Path(path));
for (FileStatus fileStatus1 : fileStatus) {
if (fileStatus1.isFile()) {
System.out.println(fileStatus1.getPath().getName() + " is file!");
} else {
System.out.println(fileStatus1.getPath().getName() + " is directory!");
}
}
} catch (IOException | InterruptedException | URISyntaxException e) {
e.printStackTrace();
} finally {
if (fs != null) {
try {
fs.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
3.3 HDFS的I/O流操作
3.3.1.HDFS文件上传
public static void putFileToHDFS(String localFile, String hdfsFile){
Configuration configuration = new Configuration();
FileSystem fs = null;
FileInputStream fis = null;
FSDataOutputStream fos = null;
try {
fs = FileSystem.get(new URI("hdfs://10.13.11.22:8020"),configuration,"hdfs");
fis = new FileInputStream(new File(localFile));
fos = fs.create(new Path(hdfsFile));
IOUtils.copyBytes(fis,fos,configuration);
} catch (IOException | InterruptedException | URISyntaxException e) {
e.printStackTrace();
} finally {
if(fs != null){
try {
fs.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(fis != null){
IOUtils.closeStream(fis);
}
if(fos != null){
IOUtils.closeStream(fos);
}
}
}
3.3.2.HDFS文件下载
- 需求：从HDFS上下载文件到本地。
- 编写代码：
public static void getFileFromHDFS(String hdfsFile, String localFile){
Configuration configuration = new Configuration();
FileSystem fs = null;
FSDataInputStream fis = null;
FileOutputStream fos = null;
try {
fs = FileSystem.get(new URI("hdfs://10.13.11.22:8020"),configuration, "hdfs");
fis = fs.open(new Path(hdfsFile));
fos = new FileOutputStream(localFile);
IOUtils.copyBytes(fis,fos,configuration);
} catch (IOException | InterruptedException | URISyntaxException e) {
e.printStackTrace();
} finally {
if(fs != null){
try {
fs.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(fis != null){
IOUtils.closeStream(fis);
}
if(fos != null){
IOUtils.closeStream(fos);
}
}
}
3.3.3.定位文件读取
- 下载文件快的第一块
public static void readFileSeek(String hdfsFile, String localFile){
Configuration configuration = new Configuration();
FileSystem fs = null;
FSDataInputStream fis = null;
FileOutputStream fos = null;
try {
fs = FileSystem.get(new URI("hdfs://10.13.11.22:8020"),configuration, "hdfs");
fis = fs.open(new Path(hdfsFile));
fos = new FileOutputStream(localFile);
byte[] buf = new byte[1024];
for(int i =0 ; i < 1024*128 ; i++){
fis.read(buf);
fos.write(buf);
}
} catch (IOException | InterruptedException | URISyntaxException e) {
e.printStackTrace();
} finally {
if(fs != null){
try {
fs.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(fis != null){
IOUtils.closeStream(fis);
}
if(fos != null){
IOUtils.closeStream(fos);
}
}
}
- 下载文件块的第二块
public static void readFileSeek2(String hdfsFile, String localFile){
Configuration configuration = new Configuration();
FileSystem fs = null;
FSDataInputStream fis = null;
FileOutputStream fos = null;
try {
fs = FileSystem.get(new URI("hdfs://10.13.11.22:8020"),configuration, "hdfs");
fis = fs.open(new Path(hdfsFile));
//从指定文件的pos位置，对文件流向前搜索。
fis.seek(1024*1024*128);
fos = new FileOutputStream(localFile);
IOUtils.copyBytes(fis,fos,configuration);
} catch (IOException | InterruptedException | URISyntaxException e) {
e.printStackTrace();
} finally {
if(fs != null){
try {
fs.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(fis != null){
IOUtils.closeStream(fis);
}
if(fos != null){
IOUtils.closeStream(fos);
}
}
}
- 合并文件
在window命令窗口中执行
type hadoop-2.7.2.tar.gz.part2 >> hadoop-2.7.2.tar.gz.part1
