JFileChooser and remote filesystems

Question

I want to add(among local file system) a few remote filesystems to JFileChooser ,
I implemented FileSytestemVIew(FileSystem) and File(RemoteFile) class.
At the first glance everything looks ok - i can see local folders and remote root folder(in combo box), when i choose remote root i can see remote folders and files, but when i invoke double click to enter remote folders, exception occurs.
for some reason JFileChooser sees 'ordinary' File - not my RemoteFile, and it treats it as a file (not folder) and wants to open it (approveSelection fires)
Probably i did not implemented all the methods that are used ..
Any ideas ? maybe there are some other ways to explore remote filesystems ?
package pl.edu.pw.browser;
import javax.swing.filechooser.FileSystemView;
import java.io.File;
import java.io.IOException;
import pl.edu.pw.fileserver.client.Client;
import java.util.*;
import javax.swing.Icon;
public class FileSystem extends FileSystemView {
public FileSystem(ArrayList servers) {
this.servers=servers;
public File createFileObject(File dir, String filename) {
System.out.println("createFileObject1");
if (dir instanceof RemoteFile )
return new RemoteFile(((RemoteFile)dir).getFtp(),dir.getAbsolutePath(), filename);
return super.createFileObject(dir,filename);
public boolean isDrive(File dir)
if (dir instanceof RemoteFile )
return false;
return super.isDrive(dir);
public boolean isFloppyDrive(File dir)
if (dir instanceof RemoteFile )
return false;
return super.isFloppyDrive(dir);
public boolean isComputerNode(File dir)
if (dir instanceof RemoteFile)
if(servers.contains(dir))
return true;
else
return false;
return super.isComputerNode(dir);
public File createFileObject(String path) {
return null;
public boolean isFileSystem(File f) {
System.out.println("isFileSystem");
if (f instanceof RemoteFile) {
return false;
} else
return super.isFileSystem(f);
public boolean isFileSystemRoot(File dir)
System.out.println("isFileSystemRoot");
if (dir instanceof RemoteFile)
if(servers.contains(dir))
return true;
else
return false;
return super.isFileSystemRoot(dir);
public boolean isRoot(File f) {
System.out.println("isRoot");
if (f instanceof RemoteFile )
if(servers.contains(f))
return true;
else
return false;
return super.isRoot(f);
public String getSystemTypeDescription(File f)
if (f instanceof RemoteFile)
return f.getName();
return super.getSystemTypeDescription(f);
public Icon getSystemIcon(File f)
return super.getSystemIcon(f);
public boolean isParent(File folder,
File file)
if (folder instanceof RemoteFile && file instanceof RemoteFile )
System.out.println("isParent("+folder.getAbsolutePath()+")("+file.getAbsolutePath()+")");
if(file.getParent().equals(folder.getAbsolutePath()))
System.out.println("is");
return true;
else
return false;
return super.isParent(folder,file);
public File getChild(File parent,
String fileName)
System.out.println("getChild");
if (parent instanceof RemoteFile )
return new RemoteFile(((RemoteFile)parent).getFtp(),parent.getAbsolutePath(),fileName);
return super.getChild(parent,fileName);
public File createNewFolder(File containingDir)
throws IOException {
System.out.println("createNewFolder");
if (containingDir instanceof RemoteFile )
return null;
return new File(containingDir,"/nowyFolder");
public String getSystemDisplayName(File f)
if (f instanceof RemoteFile )
return f.getName();
else
return super.getSystemDisplayName(f);
public File[] getRoots()
System.out.println("getRoots");
File[] files = super.getRoots();
File[] fileAll = new File[files.length+1];
int i=0;
for(i=0;i<files.length;i++)
fileAll=files[i];
fileAll[i]=createFileSystemRoot((RemoteFile)servers.get(0));
return fileAll;
public boolean isHiddenFile(File f) {
return f.isHidden();
public File getParentDirectory(File dir) {
System.out.println("getParentDirectory");
if (dir instanceof RemoteFile)
String p = dir.getParent();
if(p!=null)
return new RemoteFile(((RemoteFile)dir).getFtp(),p);
else
return null;
else
return super.getParentDirectory(dir);
protected File createFileSystemRoot(File f)
System.out.println("createFileSystemRoot");
if (f instanceof RemoteFile)
return new FileSystemRoot( (RemoteFile) f);
else
return super.createFileSystemRoot(f);
static class FileSystemRoot extends RemoteFile {
public FileSystemRoot(RemoteFile f) {
super(f.getFtp(),f.getAbsolutePath());
public File[] getFiles(File dir, boolean useFileHiding) {
if (dir instanceof RemoteFile)
RemoteFile[] files = (RemoteFile[])( (RemoteFile) dir).listFiles();
return files;
else
return dir.listFiles();
public File getHomeDirectory() {
return super.getHomeDirectory();
ArrayList servers = null;
package pl.edu.pw.browser;
import java.io.File;
import java.io.FilenameFilter;
import java.io.FileFilter;
import pl.edu.pw.fileserver.client.Client;
import java.util.*;
import java.text.*;
import pl.edu.pw.fileserver.Constants;
public class RemoteFile extends File {
final static char PATHDELIMS = '/';
public final static String absoluteStart = "//";
public RemoteFile(Client ftp, String parent) {
super(parent);
this.ftp = ftp;
path = parent;
public RemoteFile(Client ftp, String parent, String name) {
this(ftp, parent);
if (path.length()>0 && path.charAt(path.length()-1) == PATHDELIMS)
path += name;
else
path += PATHDELIMS + name;
public boolean equals(Object obj) {
if (!checked)
exists();
return path.equals(obj.toString());
public boolean isDirectory() {
if (!checked)
exists();
return isdirectory;
public boolean isFile() {
if (!checked)
exists();
return isfile;
public boolean isAbsolute() {
if (!checked)
exists();
return path.length() > 0 && path.startsWith(this.absoluteStart);
public boolean isHidden() {
if (!checked)
exists();
return ishidden;
public long lastModified() {
return modified;
public long length() {
return length;
public String[] list() {
return list(null);
public String[] list(FilenameFilter filter) {
System.out.println("list");
String[] result = null;
try{
ArrayList names = (ArrayList)ftp.dir(this.getAbsolutePath());
ArrayList files = new ArrayList();
for(int i=0;i<names.size();i++)
RemoteFile rf = new RemoteFile(ftp,(String)names.get(i));
if (filter == null || filter.accept(this,rf.getName()))
files.add(rf.getName());
result = new String[files.size()];
files.toArray(result);
catch(Exception ex)
ex.printStackTrace();
return result;
public File[] listFiles() {
FileFilter filter = null;
return listFiles(filter);
public File[] listFiles(FileFilter filter) {
System.out.println("listFiles");
RemoteFile[] result = null;
try{
ArrayList names = (ArrayList)ftp.dir(this.getAbsolutePath());
ArrayList files = new ArrayList();
for(int i=0;i<names.size();i++)
RemoteFile rf = new RemoteFile(ftp,(String)names.get(i));
rf.exists();
if (filter == null || filter.accept(rf))
files.add(rf);
result = new RemoteFile[files.size()];
System.out.println("listFiles.size="+files.size());
files.toArray(result);
catch(Exception ex)
ex.printStackTrace();
return result;
public String getPath() {
return path;
public String getCanonicalPath() {
return getAbsolutePath();
public String getAbsolutePath() {
if (!isAbsolute()) {
return ftp.pwd();
return path;
public String getName() {
String result=path;
if(result.charAt(result.length()-1) == this.PATHDELIMS)
result = result.substring(0,result.length()-1);
int i = result.lastIndexOf(this.PATHDELIMS);
if(i!=-1)
result = result.substring(i+1);
return result;
public String getParent() {
String result=path;
if(result.charAt(result.length()-1) == this.PATHDELIMS)
result = result.substring(0,result.length()-1);
int i = result.lastIndexOf(this.PATHDELIMS);
if(i<3)
return null;
result = result.substring(0,i);
return result;
public boolean exists() {
boolean ok = false;
try {
String r = ftp.exists(path);
if(r != null)
System.out.println("('"+path+"')header:"+r);
ok = true;
StringTokenizer st = new StringTokenizer(r,Constants.HEADER_SEPARATOR);
String answer = st.nextToken();
if(answer.equals(Constants.TRUE))
isfile=true;
isdirectory=false;
answer = st.nextToken();
if(answer.equals(Constants.TRUE))
canread = true;
answer = st.nextToken();
if(answer.equals(Constants.TRUE))
canwrite = true;
answer = st.nextToken();
if(answer.equals(Constants.TRUE))
ishidden = true;
answer = st.nextToken();
length = Long.parseLong(answer);
if(isfile)
answer = st.nextToken();
modified = Long.parseLong(answer);
checked = true;
catch (Exception ex) {
ex.printStackTrace();
return ok;
public boolean canRead() {
return canread;
public boolean canWrite() {
return canwrite;
public int hashCode() {
return path.hashCode() ^ 098123;
public boolean mkdir() {
return false;
public boolean renameTo(File dest) {
return false;
public Client getFtp() {
return ftp;
private Client ftp;
private boolean checked = false;
private boolean isdirectory = true;
private boolean isfile = false;
private boolean ishidden = false;
private boolean canread = false;
private boolean canwrite = false;
private String path;
private long length = 0;
private long modified =0;
java.lang.NullPointerException
     at pl.edu.pw.browser.Browser.openLocalFile(Browser.java:136)
     at pl.edu.pw.browser.component.FileChooser.approveSelection(FileChooser.java:31)
     at javax.swing.plaf.basic.BasicFileChooserUI$DoubleClickListener.mouseClicked(BasicFileChooserUI.java:412)
     at java.awt.AWTEventMulticaster.mouseClicked(AWTEventMulticaster.java:208)
     at java.awt.AWTEventMulticaster.mouseClicked(AWTEventMulticaster.java:207)
     at java.awt.Component.processMouseEvent(Component.java:5137)
     at java.awt.Component.processEvent(Component.java:4931)
     at java.awt.Container.processEvent(Container.java:1566)
     at java.awt.Component.dispatchEventImpl(Component.java:3639)
     at java.awt.Container.dispatchEventImpl(Container.java:1623)
     at java.awt.Component.dispatchEvent(Component.java:3480)
     at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:3450)
     at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3174)
     at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3095)
     at java.awt.Container.dispatchEventImpl(Container.java:1609)
     at java.awt.Window.dispatchEventImpl(Window.java:1590)
     at java.awt.Component.dispatchEvent(Component.java:3480)
     at java.awt.EventQueue.dispatchEvent(EventQueue.java:450)
     at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:197)
     at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
     at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:144)
     at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:136)
     at java.awt.EventDispatchThread.run(EventDispatchThread.java:99)

Answer 1

i solve the problem .
I did not overwrite File.getConicalFile() , this method is invoked at javax.swing.plaf.basic.BasicFileChooserUI$DoubleClickListener.mouseClicked(BasicFileChooserUI.java:412)
that is why i recived a new object type File when I was waiting for RemoteFile