在做一个hadoop项目中，利用HDFS存储日志文件。为了将未关闭的文件进行恢复，我们需要判断一个文件是否为正在打开的状态。fs.getClient().namenode.getBlockLocations(path.toUri().getPath(), 0,

fs.getFileStatus(path).getLen()).isUnderConstruction();通过这个调用可以获取是否在打开。再调用fs.recoverLease(path)去强制关闭该文件。由于我们在getBlockLocations中最初用path.toString方法去调，结果导致以下NullPointException

org.apache.hadoop.ipc.RemoteException: java.io.IOException: java.lang.NullPointerException

       at org.apache.hadoop.ipc.Client.call(Client.java:1107)
       at org.apache.hadoop.ipc.RPC$Invoker.invoke(RPC.java:226)
       at $Proxy0.getBlockLocations(Unknown Source)
       at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
       at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
       at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
       at java.lang.reflect.Method.invoke(Method.java:597)
       at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:82)
       at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:59)
       at $Proxy0.getBlockLocations(Unknown Source)
       at com.webex.da.hdc.web.DFSServlet.isOpen(DFSServlet.java:272)
       at com.webex.da.hdc.web.DFSServlet.rename(DFSServlet.java:255)
       at com.webex.da.hdc.web.DFSServlet.handleRename(DFSServlet.java:182)
       at com.webex.da.hdc.web.DFSServlet.doPost(DFSServlet.java:93)
       at javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
       at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
       at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
       at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
       at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240)
       at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:164)
       at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:462)
       at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164)