java api 访问 hadoop

首先下载elipse hadoop插件，配置好hadoop的安装目录，然后

 

map/reduce 的host一定要和mapred-core.xml 中的一致，

<property>
<name>mapred.job.tracker</name>
<value>192.168.2.39:9001</value>
</property>

dfs和core-xml 

<property>
<name>fs.default.name</name>
<value>hdfs://192.168.2.39:9000</value>
</property>

 的节点一致

这个一致，否则会出错

上传文件代码

package upload;

import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URI;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IOUtils;

public class UploadFile {

public static void main(String[] args) {
try {

//in对应的是本地文件系统的目录
InputStream in = new BufferedInputStream(new FileInputStream("C:\Users\ASUS\Desktop\sql EF.txt"));
Configuration conf = new Configuration();
//获得hadoop系统的连接
FileSystem fs = FileSystem.get(URI.create("hdfs://192.168.2.39:9000/hdfsdata/sqlEF.txt"),conf);

//out对应的是Hadoop文件系统中的目录
OutputStream out = fs.create(new Path("hdfs://192.168.2.39:9000/hdfsdata/sqlEF.txt"));
IOUtils.copyBytes(in, out, 4096,true);//4096是4k字节
System.out.println("success");
} catch (Exception e) {
System.out.println(e.toString());
}
}
}