Help me with this RMI example

Question

For Filetransfering over RMI (with compressing the data on client side and decompressing on server side) :
I have in Server-Side as a remote methode :
public byte[] getFileData(String fileName) {
System.out.println("read : "+fileName);
try {
ByteArrayOutputStream out = new ByteArrayOutputStream();
DeflaterOutputStream zipOut = new DeflaterOutputStream(out);
File f=new File(fileName);
BufferedInputStream in = new BufferedInputStream(new FileInputStream(f));
int read = 0;
int len = 0;
byte data[] = new byte[8192];
while ((read = in.read(data,0,8192)) != -1) {
zipOut.write(data,0,read);
len += read;
in.close();
zipOut.close();
System.out.println("compress-factor : "+len+" to "+out.size()+" bytes");
return out.toByteArray();
} catch (Exception e) {
System.err.println(e);
return null;
In Client-Side :
... in main programme
ServerImpl rmi = (ServerImpl)Naming.lookup(rmiName);
And i have this methode in client side in order to call the remote methode which is on server
public InputStream getFileData(String fileName) {
try {
ByteArrayInputStream zipIn = new ByteArrayInputStream(rmi.getFileData(fileName));// read file
return new InflaterInputStream(zipIn); // data decompress
} catch(NullPointerException e) {
return null; // file could not be opened
} catch(Exception e) {
return null;
My question is where should i call this method, and should i declare this one Remote methode too.
for using Client-Side i have :
==================
get a property-file :
Properties pConfig = new Properties();
URL f = null;
try {
InputStream fi = clientImpl.getFileData(PROPERTYFILE);
pConfig.load(fi);
fi.close();
} catch (Exception e) {
String err = "Can't open property-file on server : "+PROPERTYFILE+" Exception="+e;
System.out.println(err);
System.exit(1);
I have problem to know where should i put this part of code : on client side in main programe, or on server side as a remote methode wich would be called by the client.
Could some body help me to get organized with thise tree part of code.
Tank's
Astiage.

Answer 1

Here the full sourcecode of my RMI-File-Transfer pattern.
Sorry for the german comment.
File : IServerImpl.java
import java.rmi.RemoteException;
public interface IServerImpl extends java.rmi.Remote {
  public byte[] getFileData         (String pathname) throws RemoteException;
File : ServerImpl.java
/** RMI-Handler */
import java.util.Date;
import java.rmi.*;
import java.rmi.server.UnicastRemoteObject;
import java.util.zip.*;
import java.util.*;
import java.io.*;
import java.net.*;
* alle RMI's f�r den Clients und alle Aufrufe Richtung Clients
* @author Uwe G�nther
* @version 20.10.00
public class ServerImpl extends UnicastRemoteObject implements IServerImpl {
  public ServerImpl(String name) throws RemoteException {
    super();
    try {
      Naming.rebind(name+"/Server_instance",this);
    catch (Exception e) {
      if (e instanceof RemoteException) throw (RemoteException)e;
      else throw new RemoteException(e.getMessage());
   * Ab hier stehen alle Methoden Richtung Server (Aufrufe f�r den Client),
   * jeder Methodenaufruf vom Client bekommt einen eigenen Thread (dank RMI) verpasst,
   * somit k�nnen mehrere Clients eine Methode gleichzeitig aufrufen.
   * -> Nebenl�ufigkeit ist erf�llt,
   *    Methoden k�nnen mehrere Sekunden/Stunden abtauchen ohne andere Clients zu bremsen
   * Client m�chte auf Serverseite eine Datei lesen. Datei wird on-the-fly komprimiert.
   * Vor der �bertragung Richtung Client werden die Daten im DEFLATE-Format komprimiert.
   * Nach der �bertagung auf der Clientseite dekomprimiert.
   * Pfad muss nat�rlich in der Policy-Datei freigegeben sein (mit "read,write,delete").
   * z.B.:
   *  fileName = /usr/share/doc/test/properties/journal.properties
  public byte[] getFileData(String fileName) {
    System.out.println("read : "+fileName);
    try {
      // Daten laden und gleichzeitig zippen
      ByteArrayOutputStream out = new ByteArrayOutputStream();
      DeflaterOutputStream zipOut = new DeflaterOutputStream(out);
      File f=new File(fileName);
      BufferedInputStream in = new BufferedInputStream(new FileInputStream(f));
      int read = 0;
      int len = 0;
      byte data[] = new byte[8192];
      while ((read = in.read(data,0,8192)) != -1) {
        zipOut.write(data,0,read);
        len += read;
      in.close();
      zipOut.close();
      System.out.println("compress-factor : "+len+" to "+out.size()+" bytes");
      return out.toByteArray();
    } catch (Exception e) {
      System.err.println(e);
      return null;
File : Server.java
import java.net.*;
import java.io.*;
import java.util.*;
import java.lang.Thread;
import java.rmi.*;
import java.rmi.server.*;
public class Server {
  static String hostName = "localhost";
  private static int hostPort = 1099;
  static ServerImpl rmi;
  public void startHandler() {
    // RMI starten
    String s;
    try {
      if (hostPort!=java.rmi.registry.Registry.REGISTRY_PORT)         // -> es wurde ein anderer Port gew�hlt
        hostName += ":"+hostPort;
      rmi = new ServerImpl("//"+hostName);
      s = "Bindings Finished. My hostname is : "+hostName;
      System.out.println(s);
      s = "Waiting for Client requests on port "+hostPort+" ...";
      System.out.println(s);
    } catch (java.rmi.UnknownHostException uhe) {
      s = "The host computer name you have specified, "+hostName+" does not match your real computer name.";
      System.out.println(s);
      System.exit(1);
    } catch (java.rmi.RemoteException re) {
      s = "Error starting service :"+re;
      System.out.println(s);
      System.exit(1);
  public static void main(String[] args) {
    System.out.println("Server starting ...");
    Server serv = new Server();
    serv.startHandler();
File : ClientImpl.java
import java.rmi.*;
import java.rmi.server.UnicastRemoteObject;
import java.net.*;
import java.io.*;
import java.util.zip.*;
* @author Uwe G�nther
* @version 20.10.00
public class ClientImpl {
  private String rmiName = null;
  private IServerImpl js;
  /** Verbingung zum Server aufbauen */
  public ClientImpl(String host,int port) throws RemoteException {
    rmiName = "//"+host;
    if (port!=1099) rmiName += ":"+port;
    rmiName += "/Server_instance";
    try {
      js = (IServerImpl)Naming.lookup(rmiName);
      return;
    } catch (Exception e) {
      e.printStackTrace();
   * Datei auf Serversteite lesen.
   * Datenstrom ist gezippt und wird hier auch wieder entzippt.
  public InputStream getFileData(String pathFile) {
    while(true) {
      try {
        ByteArrayInputStream zipIn = new ByteArrayInputStream(js.getFileData(pathFile));// Datei laden
        return new InflaterInputStream(zipIn);            // Daten entzippen
      } catch(NullPointerException e) {
        return null;                                      // Datei konnte nicht ge�ffnet werden
      } catch(Exception e) {
        System.out.println(e);
        return null;
File : Client.java
import java.io.*;
import java.net.*;
public class Client {
  private String hostName = "localhost";
  private int hostPort = 1099;
  private ClientImpl rmi;
  public Client() {
    System.out.println("hostname :"+hostName);
    try {
      rmi = new ClientImpl(hostName,hostPort);                        // start RMI
    } catch(Exception e) {
      e.printStackTrace();
      System.exit(1);
    System.out.println("RMI connection successful");
  public static void main(String[] args) {
    Client client = new Client();
    InputStream in = client.rmi.getFileData("text.txt");
    if (in==null) {
      System.out.println("file not found !");
    } else {
      BufferedReader inBuffered = new BufferedReader(new InputStreamReader(in));
      try {
        while (true) {
          String line = inBuffered.readLine();                        // Get next line
          if (line==null) break;
          System.out.println(line);
      } catch(Exception e) {
        e.printStackTrace();
}Uwe G�nther