访问hadoop集群时错误：Access denied for user Administrator. Superuser privilege is required

hadoop集群搭建好后，本地通过java api访问hadoop集群，java代码如下（查看hadoop集群上所有节点名称信息）

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.hdfs.DistributedFileSystem;
import org.apache.hadoop.hdfs.protocol.DatanodeInfo;

import java.io.IOException;
import java.net.URI;

public class AccessHdfs {
    public static void main(String[] args) throws IOException {
        Configuration conf=new Configuration();
        FileSystem fs= FileSystem.get(URI.create("hdfs://your-ip:9000/file-path"), conf);
        DistributedFileSystem dfs = (DistributedFileSystem)fs;
        DatanodeInfo[] dataNodeStats = dfs.getDataNodeStats();

        for(int i=0; i<dataNodeStats.length; i++){
            System.out.println("DataNode_" + i + "_Node:" + dataNodeStats[i].getHostName());
        }
    }
}

出现Access denied for user Administrator. Superuser privilege is required的错误信息：

Exception in thread "main" org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.security.AccessControlException): Access denied for user Administrator. Superuser privilege is required
	at org.apache.hadoop.hdfs.server.namenode.FSPermissionChecker.checkSuperuserPrivilege(FSPermissionChecker.java:125)
	at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.checkSuperuserPrivilege(FSNamesystem.java:4484)
	at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.datanodeReport(FSNamesystem.java:4137)
	at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.getDatanodeReport(NameNodeRpcServer.java:1151)
	at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.getDatanodeReport(ClientNamenodeProtocolServerSideTranslatorPB.java:728)
	at org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java)
	at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:503)
	at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:989)
	at org.apache.hadoop.ipc.Server$RpcCall.run(Server.java:868)
	at org.apache.hadoop.ipc.Server$RpcCall.run(Server.java:814)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAs(Subject.java:422)
	at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1886)
	at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2603)

	at org.apache.hadoop.ipc.Client.call(Client.java:1470)
	at org.apache.hadoop.ipc.Client.call(Client.java:1401)
	at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:232)
	at com.sun.proxy.$Proxy9.getDatanodeReport(Unknown Source)
	at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolTranslatorPB.getDatanodeReport(ClientNamenodeProtocolTranslatorPB.java:607)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:187)
	at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:102)
	at com.sun.proxy.$Proxy10.getDatanodeReport(Unknown Source)
	at org.apache.hadoop.hdfs.DFSClient.datanodeReport(DFSClient.java:2390)
	at org.apache.hadoop.hdfs.DistributedFileSystem.getDataNodeStats(DistributedFileSystem.java:1009)
	at org.apache.hadoop.hdfs.DistributedFileSystem.getDataNodeStats(DistributedFileSystem.java:1003)
	at com.fhpt.AccessHdfs.main(AccessHdfs.java:28)

出现这个错误的原因是，Administrator用户没有权限，可以参考http://blog.sina.com.cn/s/blog_e699b42b0102xfnd.html的方式，也可以用下面的简单方式。

在代码中添加如下信息即可，其中“root”是有访问hadoop集群的权限用户名

System.setProperty("HADOOP_USER_NAME", "root");