question: public void dumpLog ( String containerId , File logFile ) throws DockerException , InterruptedException { LogStream errorStream = null ; FileChannel fileChannel = null ; FileOutputStream fileOutputStream = null ; try { if ( logFile . exists ( ) ) { logFile . delete ( ) ; } logFile . createNewFile ( ) ; fileOutputStream = new FileOutputStream ( logFile ) ; fileChannel = fileOutputStream . getChannel ( ) ; errorStream = dockerClient . logs ( containerId , LogsParam . stderr ( ) ) ; while ( errorStream . hasNext ( ) ) { LogMessage message = errorStream . next ( ) ; ByteBuffer buffer = message . content ( ) ; fileChannel . write ( buffer ) ; } } catch ( FileNotFoundException e ) { throw new DockerException ( "File " + logFile + " not found" ) ; } catch ( IOException e ) { throw new DockerException ( e ) ; } finally { if ( errorStream != null ) { errorStream . close ( ) ; } if ( fileChannel != null ) { try { fileChannel . close ( ) ; } catch ( IOException e ) { logger . error ( "Failed to close file channel" , e ) ; } } if ( fileOutputStream != null ) { try { fileOutputStream . close ( ) ; } catch ( IOException e ) { logger . error ( "Failed to close file output stream" , e ) ; } } } }
target:  Helper method for dumping error logs from Docker to file