Copy from SFTP interrupted using Apache Commons VFS

Question

I am trying to copy a file from an SFTP server using Apache Commons VFS Utility.

While copying, if there is any type of network failure, it is expected that I will get an IOException. But I am unable to find any exception thrown (checked my logs). Hence, I find a file that has been half copied. (Tried with text file.) Below is the code snippet:

public class SFTPFileHandler implements IFileSystemHandler {

    private String hostName;
    private String userName;
    private String password;
    private String knownHost;
    private String privateKey;
    private FileSystemOptions fileSystemOptions;
    private StandardFileSystemManager fileSystemManager;
    private FileObject remoteRootDirectory;
    private boolean initialized = false;
    private FileType fileType;

    //code to initialize stuff
    ....

    /**
     * Method to Connect to the Server
     * 
     * @throws URISyntaxException
     * @throws FileSystemException
     * @throws FileHandlerInitializationException
     */
    private void connect() throws URISyntaxException, FileSystemException, FileHandlerInitializationException {
        createDefaultOptions();
        String connectionUrl = buildConnectionUrl();
        remoteRootDirectory = fileSystemManager.resolveFile(connectionUrl,fileSystemOptions);
    }



    /**
     * Method to copy a from the local file system to SFTP server
     */
    public void localToRemoteCopy(String srcPath, String destPath) throws FileSystemException {
        LocalFile localFileObject = null;
        FileObject remoteFileObject = null;
        try {
            localFileObject = (LocalFile) fileSystemManager
                    .resolveFile(srcPath);
            remoteFileObject = remoteRootDirectory.resolveFile(destPath);
            remoteFileObject.copyFrom(localFileObject, new AllFileSelector());
        } finally {
            if(null != localFileObject ){
            localFileObject.close();
            }
            if(null != remoteFileObject ){
            remoteFileObject.close();
            }
        }
    }

    // other code

}

And if I look at the source, it does throw an exception.

/**
     * Copies another file to this file.
     * @param file The FileObject to copy.
     * @param selector The FileSelector.
     * @throws FileSystemException if an error occurs.
     */
    public void copyFrom(final FileObject file, final FileSelector selector)
        throws FileSystemException
    {
        if (!file.exists())
        {
            throw new FileSystemException("vfs.provider/copy-missing-file.error", file);
        }
        /* we do not alway know if a file is writeable
        if (!isWriteable())
        {
            throw new FileSystemException("vfs.provider/copy-read-only.error", new Object[]{file.getType(),
            file.getName(), this}, null);
        }
        */

        // Locate the files to copy across
        final ArrayList<FileObject> files = new ArrayList<FileObject>();
        file.findFiles(selector, false, files);

        // Copy everything across
        final int count = files.size();
        for (int i = 0; i < count; i++)
        {
            final FileObject srcFile = files.get(i);

            // Determine the destination file
            final String relPath = file.getName().getRelativeName(srcFile.getName());
            final FileObject destFile = resolveFile(relPath, NameScope.DESCENDENT_OR_SELF);

            // Clean up the destination file, if necessary
            if (destFile.exists() && destFile.getType() != srcFile.getType())
            {
                // The destination file exists, and is not of the same type,
                // so delete it
                // TODO - add a pluggable policy for deleting and overwriting existing files
                destFile.delete(Selectors.SELECT_ALL);
            }

            // Copy across
            try
            {
                if (srcFile.getType().hasContent())
                {
                    FileUtil.copyContent(srcFile, destFile);
                }
                else if (srcFile.getType().hasChildren())
                {
                    destFile.createFolder();
                }
            }
            catch (final IOException e)
            {
                throw new FileSystemException("vfs.provider/copy-file.error", new Object[]{srcFile, destFile}, e);
            }
        }
    }

and I am using the below dependencies:

        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-vfs2</artifactId>
            <version>2.0</version>
        </dependency>
        <dependency>
            <groupId>com.jcraft</groupId>
            <artifactId>jsch</artifactId>
            <version>0.1.53</version>
        </dependency>

Answer 1

I think you may be a classic example of an issue in your finally masking the true exception. I suspect if your dropping network connectivity then you are problem having clean up issues in your finally block as well. Can you try modifying your finally block so you actually catch exceptions if they are occurring in your finally block?

Change

} finally {
        if(null != localFileObject ){
        localFileObject.close();
        }
        if(null != remoteFileObject ){
        remoteFileObject.close();
        }
}

to

} finally {
        if(null != localFileObject ){
          try { 
            localFileObject.close();
          } catch (Exception ex) { //ignore or add just a logging call }
        }
        if(null != remoteFileObject ){
          try {
           remoteFileObject.close();
          } catch (Exception ex) { //ignore or add just a logging call }
        }
}

Remember an exception raised in a finally block will hide an exception thrown in your main block.

Answer 2

I was thinking of solving this problem with a manual workaround, by doing a checksum match of the source and the destination file and then throwing an exception if the checksum differed.