Remote Browsing using RMI

Question

Hi,
Read a lot of forums about how to create a Remote file browser using RMI and JFileChooser.
Not done any RMI coding I thought I'd give it a try. I have finally after 2 days managed to do it.
This is an overview.
Create a RemoteFile class that extends Remote.. eg.
import java.rmi.*;
import java.io.*;
import java.net.*;
public interface RemoteFile extends Remote {
    public boolean canRead() throws RemoteException;
    public boolean canWrite() throws RemoteException;
    public int compareTo(File pathname) throws RemoteException;etc.etc
Then create an implementation class...
import java.rmi.server.*;
import java.io.*;
import java.net.*;
public class RemoteFileImpl extends UnicastRemoteObject implements RemoteFile {
    private File f;
    public RemoteFileImpl(File sf) throws java.rmi.RemoteException {
        f=sf;
    public boolean canRead() throws java.rmi.RemoteException {
        return f.canRead();
    }etc etc for all other File functions.
Then we create a RemoteFileSystemView interface, again extending remote...
public interface RemoteFileSystemView extends Remote {
    public RemoteFile createFileObject(File dir, String filename) throws RemoteException;
    public RemoteFile createFileObject(String path) throws RemoteException;blah blah
Then An implementation class...
import javax.swing.filechooser.*;
import java.io.*;
public class RemoteFileSystemViewImpl extends java.rmi.server.UnicastRemoteObject implements RemoteFileSystemView {
    int length;
    private FileSystemView fs;
    public RemoteFileSystemViewImpl() throws java.rmi.RemoteException {
        fs=FileSystemView.getFileSystemView();
    public RemoteFile createFileObject(String path) throws java.rmi.RemoteException {
        return new RemoteFileImpl(fs.createFileObject(path));
    public RemoteFile createFileObject(java.io.File dir, String filename) throws java.rmi.RemoteException {
        return new RemoteFileImpl(fs.createFileObject(dir,filename));
    //public RemoteFileImpl createFileSystemRoot(java.io.File f) throws java.rmi.RemoteException {
    //    return new RemoteFileImpl(fs.createFileSystemRoot(f));
    public RemoteFile createNewFolder(java.io.File containingDir) throws java.rmi.RemoteException {
        RemoteFile tempf;
        try{
            tempf= new RemoteFileImpl(fs.createNewFolder(containingDir));
        } catch (IOException e){System.out.println(e); tempf=null;}
        return  tempf;
    public RemoteFile getDefaultDirectory() throws java.rmi.RemoteException {
        return new RemoteFileImpl(fs.getDefaultDirectory());
    public String[] getFiles(java.io.File dir, boolean useFileHiding) throws java.rmi.RemoteException {
        String[] tempf= new String[fs.getFiles(dir,useFileHiding).length];
        int i;
        File[] f = fs.getFiles(dir,useFileHiding);
        for(i=0;i<tempf.length;i++) tempf=f[i].toString();
return tempf;
public RemoteFile getHomeDirectory() throws java.rmi.RemoteException {
return new RemoteFileImpl(fs.getHomeDirectory());
public RemoteFile getParentDirectory(java.io.File dir) throws java.rmi.RemoteException {
return new RemoteFileImpl(fs.getParentDirectory(dir));
public String[] getRoots() throws java.rmi.RemoteException {
String[] tempf= new String[fs.getRoots().length];
System.out.println("fs is-"+fs.getRoots().length);
int i;
File[] f = fs.getRoots();
for(i=0;i<tempf.length;i++) {tempf[i]=f[i].toString();}
System.out.println("Roots="+tempf[0]);
return tempf;
public String getSystemDisplayName(java.io.File f) throws java.rmi.RemoteException {
return fs.getSystemDisplayName(f);
public javax.swing.Icon getSystemIcon(java.io.File f) throws java.rmi.RemoteException {
return fs.getSystemIcon(f);
public String getSystemTypeDescription(java.io.File f) throws java.rmi.RemoteException {
return fs.getSystemTypeDescription(f);
public boolean isComputerNode(java.io.File dir) throws java.rmi.RemoteException {
return fs.isComputerNode(dir);
public boolean isDrive(java.io.File dir) throws java.rmi.RemoteException {
return fs.isDrive(dir);
public boolean isFileSystem(java.io.File f) throws java.rmi.RemoteException {
return fs.isFileSystem(f);
public boolean isFileSystemRoot(java.io.File dir) throws java.rmi.RemoteException {
return fs.isFileSystemRoot(dir);
public boolean isFloppyDrive(java.io.File dir) throws java.rmi.RemoteException {
return fs.isFloppyDrive(dir);
public boolean isHiddenFile(java.io.File f) throws java.rmi.RemoteException {
return fs.isHiddenFile(f);
public boolean isParent(java.io.File folder, java.io.File file) throws java.rmi.RemoteException {
return fs.isParent(folder,file);
public boolean isRoot(java.io.File f) throws java.rmi.RemoteException {
return fs.isRoot(f);
public Boolean isTraversable(java.io.File f) throws java.rmi.RemoteException {
return fs.isTraversable(f);
public RemoteFile getChild(File parent, String fileName) throws java.rmi.RemoteException {
return new RemoteFileImpl(fs.getChild(parent,fileName));
Notice that whenever I should be passing a File, I pass a RemoteFile instead! Also.. when I am passing a File Array, I instead pass a String array. Reason is.. I havent managed to get File arrays through RMI.. Any Help anyone?!?!?!?!
I got round it by simply passing a String array and relying on the client to reconstruct a File array locally using the String array. Messy... perhaps.. any suggestions welcome!
Next.. use rmic to create Stubs and Skels for the 2 implementations and write an RMI server.. eg.
import java.rmi.Naming;
public class RemoteServerRMI {
    /** Creates a new instance of RemoteServerRMI */
    public RemoteServerRMI() {
        try {
            RemoteFileSystemView c = new RemoteFileSystemViewImpl();
            Naming.rebind("rmi://localhost:1099/FileService", c);
        } catch (Exception e) {
            System.out.println("Trouble: " + e);
    public static void main(String[] args) {
        new RemoteServerRMI();
}Yes.. simple and shamelessly lifted from the tutorials.
and Finally the client....
import javax.swing.filechooser.*;
import java.rmi.*;
import java.net.MalformedURLException;
import java.io.*;
import javax.swing.*;
public class RemoteFileSystemViewClient extends FileSystemView {
    static RemoteFileSystemView c;
    public RemoteFileSystemViewClient() {
        try {
            c = (RemoteFileSystemView) Naming.lookup("rmi://localhost:1099/FileService");
        catch (MalformedURLException murle) {
            System.out.println();
            System.out.println(
            "MalformedURLException");
            System.out.println(murle);
        catch (RemoteException re) {
            System.out.println();
            System.out.println(
            "RemoteException");
            System.out.println(re);
        catch (NotBoundException nbe) {
            System.out.println();
            System.out.println(
            "NotBoundException");
            System.out.println(nbe);
    public File getHomeDirectory() {
        File tempf;
        try {
            tempf= new File(c.getHomeDirectory().gettoString());
        } catch (RemoteException re){System.out.println(re);tempf=null;}
        return tempf;
    public File createFileObject(File dir, String filename) {
        File tempf;
        try {
            tempf= new File(c.createFileObject(dir, filename).gettoString());
        } catch (RemoteException re){System.out.println(re);tempf=null;}
        return tempf;
    public File createFileObject(String path) {
        File tempf;
        try {
            tempf=new File(c.createFileObject(path).gettoString());
        } catch (RemoteException re){System.out.println(re);tempf=null;}
        return tempf;
    public File createNewFolder(File containingDir) throws RemoteException {
        File tempf;
        try {
            tempf=new File(c.createNewFolder(containingDir).getAbsolutePath());
        } catch (RemoteException re){System.out.println(re);tempf=null;}
        return tempf;
    public File getChild(File parent, String fileName) {
        File tempf;
        try {
            tempf=new File(c.getChild(parent,fileName).gettoString());
        } catch (RemoteException re){System.out.println(re);tempf=null;}
        return tempf;
    public File getDefaultDirectory() {
        File tempf;
        try {
            tempf=new File(c.getDefaultDirectory().gettoString());
        } catch (RemoteException re){System.out.println(re);tempf=null;}
        return tempf;
    public File[] getFiles(File dir, boolean useFileHiding) {
        File[] tempf;
        try {
            tempf=new File[c.getFiles(dir,useFileHiding).length];
            String[] rtempf=c.getFiles(dir, useFileHiding);
            int i;
            for(i=0;i<c.getFiles(dir, useFileHiding).length;i++) tempf=new File(rtempf[i]);
} catch (RemoteException re){System.out.println(re);tempf=null;}
return tempf;
public File getParentDirectory(File dir) {
File tempf;
try {
tempf= new File(c.getParentDirectory(dir).gettoString());
} catch (RemoteException re){System.out.println(re);tempf=null;}
return tempf;
public File[] getRoots(){
File[] tempf;
try {
String[] rtempf= c.getRoots();
System.out.println("in");
tempf=new File[rtempf.length];
int i;
for(i=0;i<c.getRoots().length;i++) tempf[i]=new File(rtempf[i]);
} catch (RemoteException re){System.out.println(re);tempf=null;}
return tempf;
public String getSystemDisplayName(File f) {
String tempf;
try{
tempf=c.getSystemDisplayName(f);
} catch (RemoteException re){System.out.println(re);tempf=null;}
return tempf;
public javax.swing.Icon getSystemIcon(File f) {
javax.swing.Icon tempf;
try{
tempf=c.getSystemIcon(f);
} catch (RemoteException re){System.out.println(re);tempf=null;}
return tempf;
public String getSystemTypeDescription(File f) {
String tempf;
try {
tempf=c.getSystemTypeDescription(f);
} catch (RemoteException re){System.out.println(re);tempf=null;}
return tempf;
public boolean isComputerNode(File dir) {
boolean tempf;
try {
tempf= c.isComputerNode(dir);
} catch (RemoteException re){System.out.println(re);tempf=false;}
return tempf;
public boolean isDrive(File dir) {
boolean tempf;
try {
tempf= c.isDrive(dir);
} catch (RemoteException re){System.out.println(re);tempf=false;}
return tempf;
public boolean isFileSystem(File f) {
boolean tempf;
try {
tempf= c.isFileSystem(f);
} catch (RemoteException re){System.out.println(re);tempf=false;}
return tempf;
public boolean isFileSystemRoot(File dir) {
boolean tempf;
try {
tempf= c.isFileSystemRoot(dir);
} catch (RemoteException re){System.out.println(re);tempf=false;}
return tempf;
public boolean isFloppyDrive(File dir) {
boolean tempf;
try {
tempf= c.isFloppyDrive(dir);
} catch (RemoteException re){System.out.println(re);tempf=false;}
return tempf;
public boolean isHiddenFile(File f) {
boolean tempf;
try {
tempf= c.isHiddenFile(f);
} catch (RemoteException re){System.out.println(re);tempf=false;}
return tempf;
public boolean isParent(File folder, File file) {
boolean tempf;
try {
tempf= c.isParent(folder,file);
} catch (RemoteException re){System.out.println(re);tempf=false;}
return tempf;
public boolean isRoot(File f) {
boolean tempf;
try {
tempf= c.isRoot(f);
} catch (RemoteException re){System.out.println(re);tempf=false;}
return tempf;
public Boolean isTraversable(File f) {
Boolean tempf;
try {
tempf= c.isTraversable(f);
} catch (RemoteException re){System.out.println(re);tempf=new Boolean(false);}
return tempf;
public static void main(String[] args) {
RemoteFileSystemViewClient rc = new RemoteFileSystemViewClient();
JFileChooser fch= new JFileChooser(rc);
fch.showOpenDialog(null);
Notice.. the getFiles and getRoots, procedures, get String arrays from the RMI and reconstruct local File arrays.
I managed to browse up and down directories with this, and even.. to my surprise, create folders!
If you got any improvements please let me know at [email protected]

Answer 1

Copyright &copy; Esmond Pitt, 2007. All rights reserved.
* RemoteFileSystem.java
* Created on 13 May 2007, 14:39
import java.io.File;
import java.io.IOException;
import java.rmi.Remote;
import java.rmi.RemoteException;
import javax.swing.Icon;
* @author Esmond Pitt
public interface RemoteFileSystem extends Remote
     File createFileObject(String path) throws RemoteException;
     File[] getFiles(File dir, boolean useFileHiding) throws RemoteException;
     File createFileObject(File dir, String filename) throws RemoteException;
     File getChild(File parent, String fileName) throws RemoteException;
     boolean isFloppyDrive(File dir) throws RemoteException;
     boolean isFileSystemRoot(File dir) throws RemoteException;
     boolean isFileSystem(File f) throws RemoteException;
     boolean isDrive(File dir) throws RemoteException;
     boolean isComputerNode(File dir) throws RemoteException;
     File createNewFolder(File containingDir) throws RemoteException, IOException;
     File getParentDirectory(File dir) throws RemoteException;
     String getSystemDisplayName(File f) throws RemoteException;
     Icon getSystemIcon(File f) throws RemoteException;
     String getSystemTypeDescription(File f) throws RemoteException;
     File getDefaultDirectory() throws RemoteException;
     File getHomeDirectory() throws RemoteException;
     File[] getRoots() throws RemoteException;
     // File     createFileSystemRoot(File f) throws RemoteException;
import java.io.File;
import java.io.IOException;
import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.Icon;
import javax.swing.filechooser.FileSystemView;
* @author Esmond Pitt
* @version $Revision: 3 $
public class RemoteFileSystemServer extends UnicastRemoteObject implements RemoteFileSystem
     private FileSystemView     fs = FileSystemView.getFileSystemView();
     private Logger     logger = Logger.getLogger(this.getClass().getName());
     /** Creates a new instance of RemoteFileSystemServer */
     public RemoteFileSystemServer(int port) throws RemoteException
          super(port);
          logger.log(Level.INFO, "exported on port {0} and receiving calls fs={1}", new Object[]{port, fs});
     public File createFileObject(String path)
          logger.log(Level.FINE, "createFileObject({0})", path);
          return fs.createFileObject(path);
     public File createFileObject(File dir, String filename)
          logger.log(Level.FINE, "createFileObject({0},{1})", new Object[]{dir, filename});
          return fs.createFileObject(dir, filename);
     public File[] getFiles(File dir, boolean useFileHiding)
          logger.log(Level.FINE, "getFiles({0},{1})", new Object[]{dir, useFileHiding});
          return fs.getFiles(dir, useFileHiding);
     public File getChild(File parent, String fileName)
          logger.log(Level.FINE, "getChild({0},{1})", new Object[]{parent, fileName});
          return fs.getChild(parent, fileName);
     public boolean isFloppyDrive(File dir)
          logger.log(Level.FINE, "isFloppyDrive({0})", dir);
          return fs.isFloppyDrive(dir);
     public boolean isFileSystemRoot(File dir)
          logger.log(Level.FINE, "isFileSystemRoot({0})", dir);
          return fs.isFileSystemRoot(dir);
     public boolean isFileSystem(File f)
          logger.log(Level.FINE, "isFileSystem({0})", f);
          return fs.isFileSystem(f);
     public boolean isDrive(File dir)
          logger.log(Level.FINE, "isDrive({0})", dir);
          return fs.isDrive(dir);
     public boolean isComputerNode(File dir)
          logger.log(Level.FINE, "isComputerNode({0})", dir);
          return fs.isComputerNode(dir);
     public File createNewFolder(File containingDir) throws IOException
          logger.log(Level.FINE, "createNewFolder({0})", containingDir);
          return fs.createNewFolder(containingDir);
     public File getParentDirectory(File dir)
          logger.log(Level.FINE, "getParentDirectory({0})", dir);
          return fs.getParentDirectory(dir);
     public String getSystemDisplayName(File f)
          logger.log(Level.FINE, "getSystemDisplayName({0})", f);
          return fs.getSystemDisplayName(f);
     public Icon getSystemIcon(File f)
          logger.log(Level.FINE, "getSystemIcon({0})", f);
          return fs.getSystemIcon(f);
     public String getSystemTypeDescription(File f)
          logger.log(Level.FINE, "getSystemTypeDescription({0})", f);
          return fs.getSystemTypeDescription(f);
     public File getDefaultDirectory()
          logger.log(Level.FINE, "getDefaultDirectory()");
          return fs.getDefaultDirectory();
     public File getHomeDirectory()
          logger.log(Level.FINE, "getHomeDirectory()");
          return fs.getHomeDirectory();
     public File[] getRoots()
          logger.log(Level.FINE, "getRoots()");
          return fs.getRoots();
      public File createFileSystemRoot(File f)
          return fs.createFileSystemRoot(f);
import java.io.File;
import java.io.IOException;
import java.net.MalformedURLException;
import java.rmi.Naming;
import java.rmi.NotBoundException;
import java.rmi.RemoteException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.Icon;
import javax.swing.filechooser.FileSystemView;
* @author Esmond Pitt
* @version $Revision: 4 $
public class RemoteFileSystemView extends FileSystemView
     private Logger     logger = Logger.getLogger(this.getClass().getName());
     private RemoteFileSystem     fs;
     public RemoteFileSystemView(String host)
     throws NotBoundException, RemoteException, MalformedURLException
          String     url = "rmi://"+host+"/"+RemoteFileSystem.class.getName();
          this.fs = (RemoteFileSystem)Naming.lookup(url);
          logger.log(Level.INFO, "Connected to {0} via {1}", new Object[]{url, fs});
     public File createFileObject(String path)
          logger.entering(this.getClass().getName(), "createFileObject", path);
          try
               return fs.createFileObject(path);
          catch (RemoteException exc)
               logger.log(Level.SEVERE, "path="+path, exc);
               return null;
     public File[] getFiles(File dir, boolean useFileHiding)
          logger.entering(this.getClass().getName(), "getFiles", new Object[]{dir, useFileHiding});
          try
               return fs.getFiles(dir, useFileHiding);
          catch (RemoteException exc)
               logger.log(Level.SEVERE, "dir="+dir+" useFileHiding="+useFileHiding, exc);
               return null;
     public File createFileObject(File dir, String filename)
          logger.entering(this.getClass().getName(), "createFileObject", new Object[]{dir, filename});
          try
               return fs.createFileObject(dir, filename);
          catch (RemoteException exc)
               logger.log(Level.SEVERE, "dir="+dir+" filename="+filename, exc);
               return null;
     public File getChild(File parent, String fileName)
          logger.entering(this.getClass().getName(), "getChild", new Object[]{parent, fileName});
          try
               return fs.getChild(parent, fileName);
          catch (RemoteException exc)
               logger.log(Level.SEVERE, "parent="+parent+" fileName="+fileName, exc);
               return null;
     public boolean isFloppyDrive(File dir)
          logger.entering(this.getClass().getName(), "isFloppyDrive", dir);
          try
               return fs.isFloppyDrive(dir);
          catch (RemoteException exc)
               logger.log(Level.SEVERE, "dir="+dir, exc);
               return false;
     public boolean isFileSystemRoot(File dir)
          logger.entering(this.getClass().getName(), "isFileSystemRoot", dir);
          try
               return fs.isFileSystemRoot(dir);
          catch (RemoteException exc)
               logger.log(Level.SEVERE, "dir="+dir, exc);
               return false;
     public boolean isFileSystem(File file)
          logger.entering(this.getClass().getName(), "isFileSystem", file);
          try
               return fs.isFileSystem(file);
          catch (RemoteException exc)
               logger.log(Level.SEVERE, "file="+file, exc);
               return false;
     public boolean isDrive(File dir)
          logger.entering(this.getClass().getName(), "isDrive", dir);
          try
               return fs.isDrive(dir);
          catch (RemoteException exc)
               logger.log(Level.SEVERE, "dir="+dir, exc);
               return false;
     public boolean isComputerNode(File dir)
          logger.entering(this.getClass().getName(), "isComputerNode", dir);
          try
               return fs.isComputerNode(dir);
          catch (RemoteException exc)
               logger.log(Level.SEVERE, "dir="+dir, exc);
               return false;
     public File createNewFolder(File containingDir) throws IOException
          logger.entering(this.getClass().getName(), "createNewFolder", containingDir);
          try
               return fs.createNewFolder(containingDir);
          catch (RemoteException exc)
               logger.log(Level.SEVERE, "containingDir="+containingDir, exc);
               return null;
     public File getParentDirectory(File dir)
          logger.entering(this.getClass().getName(), "getParentDirectory", dir);
          try
               return fs.getParentDirectory(dir);
          catch (RemoteException exc)
               logger.log(Level.SEVERE, "dir="+dir, exc);
               return null;
     public String getSystemDisplayName(File file)
          logger.entering(this.getClass().getName(), "getSystemDisplayName", file);
          try
               return fs.getSystemDisplayName(file);
          catch (RemoteException exc)
               logger.log(Level.SEVERE, "file="+file, exc);
               return null;
     public Icon getSystemIcon(File file)
          logger.entering(this.getClass().getName(), "getSystemIcon", file);
          try
               return fs.getSystemIcon(file);
          catch (RemoteException exc)
               logger.log(Level.SEVERE, "file="+file, exc);
               return null;
     public String getSystemTypeDescription(File file)
          logger.entering(this.getClass().getName(), "getSystemTypeDescription", file);
          try
               return fs.getSystemTypeDescription(file);
          catch (RemoteException exc)
               logger.log(Level.SEVERE, "file="+file, exc);
               return null;
     public File getDefaultDirectory()
          logger.entering(this.getClass().getName(), "getDefaultDirectory");
          try
               return fs.getDefaultDirectory();
          catch (RemoteException exc)
               logger.log(Level.SEVERE, "getDefaultDirectory()", exc);
               return null;
     public File getHomeDirectory()
          logger.entering(this.getClass().getName(), "getHomeDirectory");
          try
               return fs.getHomeDirectory();
          catch (RemoteException exc)
               logger.log(Level.SEVERE, "getHomeDirectory()", exc);
               return null;
     public File[] getRoots()
          logger.entering(this.getClass().getName(), "getRoots");
          try
               return fs.getRoots();
          catch (RemoteException exc)
               logger.log(Level.SEVERE, "getRoots()", exc);
               return null;
     protected File createFileSystemRoot(File file)
          logger.entering(this.getClass().getName(), "createFileSystemRoot", file);
          logger.log(Level.SEVERE, "createFileSystemRoot called with ({0})", new Object[]{file});
          try
               return fs.createFileSystemRoot(file);
          catch (RemoteException exc)
               logger.log(Level.SEVERE, "", exc);
          return null;
}