在使用Java连接hbase的时候，抛出异常，一开始是因为自己没有启动zookeeper报的错，后面了解到hbase是强依赖与zookeeper的，后面我就启动了zookeeper，就没有报错了，但是就报错说我的Master节点没有运行，但是我的hadoop集群也是启动了，jps发现所有的进程都是存在的。就很离谱，在网上找了半天的原因也没有找到。最后，还是找到了解决方法。希望对各位博友有所帮助。
一开始是在这个地方卡住了十分钟左右，然后就报错误。
运行代码报错：
log4j:WARN No appenders could be found for logger (org.apache.hadoop.security.Groups).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
Exception in thread "main" org.apache.hadoop.hbase.client.RetriesExhaustedException: Failed after attempts=16, exceptions:
2023-05-12T01:51:49.588Z, RpcRetryingCaller{globalStartTime=2023-05-12T01:51:47.171Z, pause=100, maxAttempts=16}, org.apache.hadoop.hbase.MasterNotRunningException: java.net.UnknownHostException: can not resolve hadoopmaster,16000,1683852045767
2023-05-12T01:51:49.738Z, RpcRetryingCaller{globalStartTime=2023-05-12T01:51:47.171Z, pause=100, maxAttempts=16}, org.apache.hadoop.hbase.MasterNotRunningException: java.net.UnknownHostException: can not resolve hadoopmaster,16000,1683852045767
2023-05-12T01:51:49.941Z, RpcRetryingCaller{globalStartTime=2023-05-12T01:51:47.171Z, pause=100, maxAttempts=16}, org.apache.hadoop.hbase.MasterNotRunningException: java.net.UnknownHostException: can not resolve hadoopmaster,16000,1683852045767
2023-05-12T01:51:50.245Z, RpcRetryingCaller{globalStartTime=2023-05-12T01:51:47.171Z, pause=100, maxAttempts=16}, org.apache.hadoop.hbase.MasterNotRunningException: java.net.UnknownHostException: can not resolve hadoopmaster,16000,1683852045767
2023-05-12T01:51:50.751Z, RpcRetryingCaller{globalStartTime=2023-05-12T01:51:47.171Z, pause=100, maxAttempts=16}, org.apache.hadoop.hbase.MasterNotRunningException: java.net.UnknownHostException: can not resolve hadoopmaster,16000,1683852045767
2023-05-12T01:51:51.759Z, RpcRetryingCaller{globalStartTime=2023-05-12T01:51:47.171Z, pause=100, maxAttempts=16}, org.apache.hadoop.hbase.MasterNotRunningException: java.net.UnknownHostException: can not resolve hadoopmaster,16000,1683852045767
2023-05-12T01:51:53.780Z, RpcRetryingCaller{globalStartTime=2023-05-12T01:51:47.171Z, pause=100, maxAttempts=16}, org.apache.hadoop.hbase.MasterNotRunningException: java.net.UnknownHostException: can not resolve hadoopmaster,16000,1683852045767
2023-05-12T01:51:57.796Z, RpcRetryingCaller{globalStartTime=2023-05-12T01:51:47.171Z, pause=100, maxAttempts=16}, org.apache.hadoop.hbase.MasterNotRunningException: java.net.UnknownHostException: can not resolve hadoopmaster,16000,1683852045767
2023-05-12T01:52:10.160Z, RpcRetryingCaller{globalStartTime=2023-05-12T01:51:47.171Z, pause=100, maxAttempts=16}, org.apache.hadoop.hbase.MasterNotRunningException: java.net.UnknownHostException: can not resolve hadoopmaster,16000,1683852045767
2023-05-12T01:52:22.509Z, RpcRetryingCaller{globalStartTime=2023-05-12T01:51:47.171Z, pause=100, maxAttempts=16}, org.apache.hadoop.hbase.MasterNotRunningException: java.net.UnknownHostException: can not resolve hadoopmaster,16000,1683852045767
2023-05-12T01:52:34.842Z, RpcRetryingCaller{globalStartTime=2023-05-12T01:51:47.171Z, pause=100, maxAttempts=16}, org.apache.hadoop.hbase.MasterNotRunningException: java.net.UnknownHostException: can not resolve hadoopmaster,16000,1683852045767
2023-05-12T01:52:47.224Z, RpcRetryingCaller{globalStartTime=2023-05-12T01:51:47.171Z, pause=100, maxAttempts=16}, org.apache.hadoop.hbase.MasterNotRunningException: java.net.UnknownHostException: can not resolve hadoopmaster,16000,1683852045767
2023-05-12T01:53:09.691Z, RpcRetryingCaller{globalStartTime=2023-05-12T01:51:47.171Z, pause=100, maxAttempts=16}, org.apache.hadoop.hbase.MasterNotRunningException: java.net.UnknownHostException: can not resolve hadoopmaster,16000,1683852045767
2023-05-12T01:53:32.119Z, RpcRetryingCaller{globalStartTime=2023-05-12T01:51:47.171Z, pause=100, maxAttempts=16}, org.apache.hadoop.hbase.MasterNotRunningException: java.net.UnknownHostException: can not resolve hadoopmaster,16000,1683852045767
2023-05-12T01:53:54.623Z, RpcRetryingCaller{globalStartTime=2023-05-12T01:51:47.171Z, pause=100, maxAttempts=16}, org.apache.hadoop.hbase.MasterNotRunningException: java.net.UnknownHostException: can not resolve hadoopmaster,16000,1683852045767
2023-05-12T01:54:16.981Z, RpcRetryingCaller{globalStartTime=2023-05-12T01:51:47.171Z, pause=100, maxAttempts=16}, org.apache.hadoop.hbase.MasterNotRunningException: java.net.UnknownHostException: can not resolve hadoopmaster,16000,1683852045767
at org.apache.hadoop.hbase.client.RpcRetryingCallerImpl.callWithRetries(RpcRetryingCallerImpl.java:146)
at org.apache.hadoop.hbase.client.HBaseAdmin.executeCallable(HBaseAdmin.java:3018)
at org.apache.hadoop.hbase.client.HBaseAdmin.executeCallable(HBaseAdmin.java:3010)
at org.apache.hadoop.hbase.client.HBaseAdmin.createNamespaceAsync(HBaseAdmin.java:2153)
at org.apache.hadoop.hbase.client.Admin.createNamespace(Admin.java:1773)
at com.haolin.HBaseDDL.createNamespace(HBaseDDL.java:34)
at com.haolin.HBaseDDL.main(HBaseDDL.java:63)
Caused by: org.apache.hadoop.hbase.MasterNotRunningException: java.net.UnknownHostException: can not resolve hadoopmaster,16000,1683852045767
at org.apache.hadoop.hbase.client.ConnectionImplementation$MasterServiceStubMaker.makeStub(ConnectionImplementation.java:1286)
at org.apache.hadoop.hbase.client.ConnectionImplementation.getKeepAliveMasterService(ConnectionImplementation.java:1345)
at org.apache.hadoop.hbase.client.ConnectionImplementation.getMaster(ConnectionImplementation.java:1334)
at org.apache.hadoop.hbase.client.MasterCallable.prepare(MasterCallable.java:57)
at org.apache.hadoop.hbase.client.RpcRetryingCallerImpl.callWithRetries(RpcRetryingCallerImpl.java:106)
... 6 more
Caused by: java.net.UnknownHostException: can not resolve hadoopmaster,16000,1683852045767
at org.apache.hadoop.hbase.ipc.AbstractRpcClient.createAddr(AbstractRpcClient.java:435)
at org.apache.hadoop.hbase.ipc.AbstractRpcClient.createBlockingRpcChannel(AbstractRpcClient.java:513)
at org.apache.hadoop.hbase.client.ConnectionImplementation$MasterServiceStubMaker.lambda$makeStubNoRetries$0(ConnectionImplementation.java:1261)
at org.apache.hadoop.hbase.util.ConcurrentMapUtils.computeIfAbsentEx(ConcurrentMapUtils.java:61)
at org.apache.hadoop.hbase.client.ConnectionImplementation$MasterServiceStubMaker.makeStubNoRetries(ConnectionImplementation.java:1260)
at org.apache.hadoop.hbase.client.ConnectionImplementation$MasterServiceStubMaker.makeStub(ConnectionImplementation.java:1280)
解决方法是在Windows的hosts文件里面添加hadoop集群主节点的映射，我的hadoop主节点的名字是HadoopMaster，ip是192.168.19.63.
打开C:\Windows\System32\drivers\etc目录，直接打开host文件是无法保存的，需要有管理员的权限。当然可以使用管理员的方式打开自己的文件管理系统即可打开hosts文件。
然后按住win+x键，点击命令提示符，输入notepad
接着点击打开
点击选择文件类型为所有文件类型
打开host文件，添加自己hadoop集群的master信息
最后重新运行即可成功运行API。