How to implement custom SftpSimplePatternFileListFilter? - spring

Question

I am newbee to Spring integration. i am trying to implement customer sftp filter to list the files in SFTP server. I am getting "The blank final field seen may not have been initialized" at the constructor.Can you please suggest me to get list of file names from sftp server.
I dont have any idea what went wrong in my code.
Thanks in Advance
java code
public class SFTPFileFilter extends SftpSimplePatternFileListFilter {
public SFTPFileFilter(String pattern) {
super(pattern);
// TODO Auto-generated constructor stub
}
final static Logger logger = LoggerFactory.getLogger(SFTPFileFilter.class);
private final Queue<File> seen;
private final Set<File> seenSet = new HashSet<File>();
private final Object monitor = new Object();
public static int fileCount = 0;
#Autowired
private SourcePollingChannelAdapter sftpInbondAdapter;
public List<File> filterFiles(File[] files)
{
List<File> accepted = new ArrayList<File>();
for (File file : files) {
System.out.println(file.getName());
accepted.add(file);
}
return accepted;
}
public boolean accept(File file) {
synchronized (this.monitor) {
if (this.seenSet.contains(file)) {
logger.info(file.getName()+" is already copied earlier");
return false;
}
if (this.seen != null) {
if (!this.seen.offer(file)) {
File removed = this.seen.poll();
this.seenSet.remove(removed);
this.seen.add(file);
}
}
this.seenSet.add(file);
return true;
}
}
}

Answer 1

private final Queue<File> seen;
You are not initializing that field in a constructor.
You can't extend it like that; simply override the method like this...
public List<File> filterFiles(File[] files) {
for (File file : files) {
System.out.println("received:" + file.getName());
}
List<File> filtered = super.filterFiles(files);
for (File file : flteredFiles) {
System.out.println("after filter:" + file.getName());
}
return filteredFiles;
}