老师，那个java操作，创建目录是可以的，但是 读hdfs 文件内容 读不下来，还有上传到 hdfs文件，我用的是阿里云的centos7.2搭建的 Hadoop cdh 2.60版本。jar包和
安装的hadoop版本一致。且启动节点和端口都是正常的。
1、
这里执行创建的操作，在 hdfs根目录可以看到 a.txt 文件但是无内容
FSDataOutputStream out= fileSystem.create(new Path("/a.txt"));
out.write(“test_java_api”.getBytes());
out.flush();
out.close();
出现异常：
org.apache.hadoop.ipc.RemoteException(java.io.IOException): File /a.txt could only be replicated to 0 nodes instead of minReplication (=1). There are 1 datanode(s) running and 1 node(s) are excluded in this operation.
2、百度说，加上下面这句话
configuration.set(“dfs.client.use.datanode.hostname”, “true”);//让可以使用主机名传参数
但是：会报新的异常
java.io.IOException: DataStreamer Exception:

atorg.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.run(DFSOutputStream.java:696)

Caused by: java.nio.channels.UnresolvedAddressException
at sun.nio.ch.Net.checkAddress(Net.java:101)
at sun.nio.ch.SocketChannelImpl.connect(SocketChannelImpl.java:622)
at org.apache.hadoop.net.SocketIOWithTimeout.connect(SocketIOWithTimeout.java:192)at org.apache.hadoop.net.NetUtils.connect(NetUtils.java:530)
atorg.apache.hadoop.hdfs.DFSOutputStream.createSocketForPipeline(DFSOutputStream.java:1610)
atorg.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.createBlockOutputStream(DFSOutputStream.java:1408)atorg.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.nextBlockOutputStream(DFSOutputStream.java:1361) atorg.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.run(DFSOutputStream.java:588)