java.lang.ClassNotFoundException : Class org. apache.hadoop.hdfs.DistributedFileSystem

Question

我想使用hadoop-3.0运行以下程序:

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;


public class HDFSFileTest {
public static void main(String[]args) {
    try {
        String fileName="input/test.txt";
        Configuration conf =new Configuration();
        conf.set("fs.defaultFS","hdfs://localhost:9000");
    conf.set("fs.hdfs.impl","org.apache.hadoop.hdfs.DistributedFileSystem");
        FileSystem fs=FileSystem.get(conf);
        if(fs.exists(new Path(fileName))) {
            System.out.println("File exists!");
        }
        else {
            System.out.println("File not exists!");
        }
    }
    catch(Exception e){
        e.printStackTrace();
    }
}
}

但是当我在 eclipse 中执行代码时出现异常:

log4j:WARN No appenders could be found for logger 
(org.apache.hadoop.util.Shell).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for 
more info.
java.lang.RuntimeException: java.lang.ClassNotFoundException: Class 
org.apache.hadoop.hdfs.DistributedFileSystem not found
at org.apache.hadoop.conf.Configuration.getClass(Configuration.java:2559)
at org.apache.hadoop.fs.FileSystem.getFileSystemClass(FileSystem.java:3254)
at org.apache.hadoop.fs.FileSystem.createFileSystem(FileSystem.java:3286)
at org.apache.hadoop.fs.FileSystem.access$200(FileSystem.java:123)
at org.apache.hadoop.fs.FileSystem$Cache.getInternal(FileSystem.java:3337)
at org.apache.hadoop.fs.FileSystem$Cache.get(FileSystem.java:3305)
at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:476)
at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:225)
at HDFSFileTest.main(HDFSFileTest.java:13)
Caused by: java.lang.ClassNotFoundException: Class 
org.apache.hadoop.hdfs.DistributedFileSystem not found
at 

我检查了hadoop-common-3.0.1.jar、hadoop-hdfs-3.0.1.jar包，没有这样的类

 org.apache.hadoop.hdfs.DistributedFileSystem

Answer 1

也许你们只需要添加一些其他 jar 。

我之前也遇到过同样的问题，然后我碰巧添加了一些其他 jar ，如下所示。幸运的是，我成功了。