NullpointerException on downloadFile (starts with version 0.34)

[Martin Schlesier]

We use SSHJ to download files from a SFTP-Server and used a long time the version 0.19.
Now we upgrade to version 0.36 and become a NullpointerException on downloading a file.
I tested other versions and the version 0.33 works but with 0.34 the Nullpointer is thrown.

Here is the Stacktrace:

Any ideas what has changed in version 0.34 and not working with our code?

Update:
I found the Nullpointer in the Implementation of "InMemoryDestFile":

What is the correct Implementation for "getLength()" and "getOutputStream(boolean append)"?

[Jeroen van Erp]

The StreamingInMemoryDestFile is not part of SSHJ.

The method that contains line 172 which you indicate contains the following code in 0.34.0:

sshj/src/main/java/net/schmizz/sshj/sftp/SFTPFileTransfer.java

Lines 153 to 178 in ec467a3

 private LocalDestFile downloadFile(final StreamCopier.Listener listener, 
                                    final RemoteResourceInfo remote, 
                                    final LocalDestFile local, 
                                    final long byteOffset) 
         throws IOException { 
     final LocalDestFile adjusted = local.getTargetFile(remote.getName()); 
     final RemoteFile rf = engine.open(remote.getPath()); 
     try { 
         log.debug("Attempting to download {} with offset={}", remote.getPath(), byteOffset); 
         final RemoteFile.ReadAheadRemoteFileInputStream rfis = rf.new ReadAheadRemoteFileInputStream(16, byteOffset); 
         final OutputStream os = adjusted.getOutputStream(byteOffset != 0); 
         try { 
             new StreamCopier(rfis, os, engine.getLoggerFactory()) 
                     .bufSize(engine.getSubsystem().getLocalMaxPacketSize()) 
                     .keepFlushing(false) 
                     .listener(listener) 
                     .copy(); 
         } finally { 
             rfis.close(); 
             os.close(); 
         } 
     } finally { 
         rf.close(); 
     } 
     return adjusted; 
 } 

This just closes the outputstream that is assigned at L163.

Not sure how that can be null if you're actually indeed passing in that StreamingInMemoryDestFile

[Martin Schlesier]

Thanks @hierynomus .
My comment "before NULL" means that I returned NULL before. 😅
Now i set "getOutputStream()" and my question is if that is correct and what could the correct Implementation for "getLength()" and "getOutputStream(boolean append)"?

[Jeroen van Erp]

I'd say it depends, I'm not sure you you use the library. The append flag is there when you're resuming a downloaded file, so with append=true you'd expect the current implementation that returns the outputStream. With append=false you would expect to set and return a new or truncated outputstream, so that there's no previous contents.
The getLength looks fine.

[Martin Schlesier]

Thanks. I will try it.