RMI Remote Observer
Sorry for the cross-post but getting answers out of the JINI forum is like pulling teeth...
I'm looking to improve performance of an application I wrote which has a server generating remote events and distributing them to clients who have previously signaled interest. One thing I noticed is that when one of the clients has a slow connection the whole system suffers. So I was wondering if introducing a threaded architecture would help in the following piece of code.
currently...
Iterator hashMapKeySetIterator = hashMap.keySet().iterator();
while ( hashMapKeySetIterator.hasNext() )
Object key = hashMapKeySetIterator.next();
Observer observer = (Observer)hashMap.get(key);
try
observer.notify( event[] ); <-------- Thread this???????
} catch (RemoteException re)
try
removeObserver( key, observer );
}catch(Exception e)
//handle exception
System.out.println("Provider.notify() Error --> " + re.getMessage() );
So, if I instead just created a new thread for each of the calls to notify(), would that improve the overall performance? Would it introduce any problem areas or would there be anything I should be concerned about? Thanks in advance.
Dave
Yes. Your solution seems to be the way to solve this type of problem.
I would recommend some type of Thread pool so that you don't have as much Thread creation overhead.
Similar Messages
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Help needed to move a java.rmi.Remote object.....
Hi,
I have an object extending java.rmi.Remote on a server. I want to get it onto a client (ie the actual object, not a reference to the object on the server).
The catch (isn't there always one):
The client must only get class definitions/interface definitions from the java.rmi.server.codebase
(ie I don't want to use a network classloader).
Anyone any ideas?
Kev.If you have a class that implements java.rmi.Remote then the objects of that class by definition are available for Remote access (ie, they are passed by reference). Remote objects can't be passed by value. However, if you want objects of a particular class to be passed by value you could have the class implement java.io.Serializable instead of java.rmi.Remote.
Hope this helps. -
Hello,
I recently wrote a simply Infobus applet which includes a
LoginDialog.
1.when i run it in Jdeveloper(not be packed into .jar
or .zip), i can login but get a error:"java.lang.OutofMemory",
however,the frame will appear slowly when i reload the applet.
(128M RAM in my PC).
2.when i deployed it into myjar2.jar ,then run it in
Jdeveloper, I can't login and get a error:"Named Connection cn1
not be opened", (myjar2.jar includes the
files: "connections.properties", "cn1.xml","Applet2.class ",etc .
3.when i run it from client browser(IE5 & Netscape 4.7) after
deployed,i can see the LoginDialog ,but can't login and get
error:"java.rmi.remote".
Please help me to resolve!
Thanks!
nullHi,
When you run from within JDeveloper, make sure you are running
the HTML file rather than the applet.java file. I have had
better luck when using the HTML file to run, especially with the
login dialog.
When you run from a browser externally, make sure you are using
the JDK 1.2 plugin. I think the release notes contain
information on where to get it and how to use it.
Laura
lxd (guest) wrote:
: Hello,
: I recently wrote a simply Infobus applet which includes a
: LoginDialog.
: 1.when i run it in Jdeveloper(not be packed into .jar
: or .zip), i can login but get a error:"java.lang.OutofMemory",
: however,the frame will appear slowly when i reload the applet.
: (128M RAM in my PC).
: 2.when i deployed it into myjar2.jar ,then run it in
: Jdeveloper, I can't login and get a error:"Named Connection cn1
: not be opened", (myjar2.jar includes the
: files: "connections.properties", "cn1.xml","Applet2.class ",etc
: 3.when i run it from client browser(IE5 & Netscape 4.7)
after
: deployed,i can see the LoginDialog ,but can't login and get
: error:"java.rmi.remote".
: Please help me to resolve!
: Thanks!
null -
Error class rmi.Remote not found
I m using a RMI chat in an apllication in tomcat, the chat applet doesn t appear : Error classNotFound rmi.Remote. I don t understand why ?? It should show something before trying to connect.
If it works in appletviewer but not in the browser, it's usually because the browser is not using the same JVM as appletviewer is, OR that the applet is trying to do things not normally allowed by the security model for applets. In this case, it's probably that your browser is using the old Microsoft JVM - get the Java Plug-in and configure it to be used by your browser.
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RMI Remote reference is getting garbage collected
Hi,
I'm using Weblogic 5.1, on Windows NT.
I have RMI remote object on the server side, and my client is an applet.
In the applet I use JNDI to get the reference of the server object, and
use it. The problem is after sometime ( like 10 min or so) I get
weblogic.rmi.NoSuchObjectException
and at the WLServer console I see
' <DGCServer> tried to renew lease for 1 lost reference'.
At the server side, I bind the object using JNDI.
I want thsi reference to be available all the time in the applet.
any help is appreciated.
thanks,
Abdul.Refer to my post on misc. Do not cross-post.
Cheers - Wei
aroshan <@cisco.com> wrote in message news:[email protected]..
Hi,
I'm using Weblogic 5.1, on Windows NT.
I have RMI remote object on the server side, and my client is an applet.
In the applet I use JNDI to get the reference of the server object, and
use it. The problem is after sometime ( like 10 min or so) I get
weblogic.rmi.NoSuchObjectException
and at the WLServer console I see
' <DGCServer> tried to renew lease for 1 lost reference'.
At the server side, I bind the object using JNDI.
I want thsi reference to be available all the time in the applet.
any help is appreciated.
thanks,
Abdul. -
Check java.rmi.Remote client alive?
Hi,
I have a Client program which extends java.rmi.Remote and a Server program which has a method Connect(java.rmi.Remote client).
in my Server program, I add the "java.rmi.Remote client" stub reference into a vector when any client calls the remote method Connect(java.rmi.Remote client).
when I am trying to check if the client is still alive, how could i make use of the stub reference to do so? I have check if the reference is null but it doesn't work.
Thank you for any help.I am checking on the client without client knowing it. i need to use this when any of the client call my server method to shut down.
i will need to check that no client are connected or alive before shutting down the server. this is why the operation have to be transparent to all other client.
Yet i could not change the callback interface as it has been published and there are all sort of clients connecting to the server using this interface.
Probably could I achieve that using socket connection ?
i would appreciate if someone could suggest a solution to it. Thank you.
Message was edited by:
eddy_nyp -
I have developed an RMI application with client an server running on the same machine,and it works fine. but when I try to deploy the client remotely(from a different machine), it does not even get to execute. My guess is that when invoke MyremoteInterface c=(MyremoteInterface)myreg.lookup("calculator"); on the client side, it does not recognize MyremoteInterface. When done on the same machine, I do have to import the remote interface in the client package. should I do the same thing remotely? if so how?
Thank you.No need to guess. Post the exception and stack trace here. Or whatever you're observing that isn't expected.
-
Rmi remote reference lookup very slow in web start application
I have a little problem with the RMI communication in a web start test application.
It is a very simple program in which the client calls a remote object that returns a String.
Everything seems to be working fine when i'm running/debugging the client app in eclipse, but when i package my client project into a jar file and run it as a web start application (i'm providing the jnlp on a local webserver) the remote reference lookup takes about 15 seconds.
basically, what my client does is this:
Registry registry = LocateRegistry.getRegistry(address);
ServerTransaction st= (ServerTransaction) registry.lookup(name);
String result = st.test();
The server code looks like this:
String name = "ServerTransaction";
ServerTransaction engine = new DefaultServerTransaction();
ServerTransaction stub = (ServerTransaction) UnicastRemoteObject.exportObject(engine, 0);
Registry registry = LocateRegistry.createRegistry(Registry.REGISTRY_PORT);
registry.rebind(name, stub);
The server runs as a normal stand alone java application on my local machine as well.
And here the content of the jnlp file for the client application:
<resources>
<jar href="WSTest.jar"/>
<jar href="WSTestServer.jar"/>
<j2se version="1.6+" href="http://java.sun.com/products/autodl/j2se"/>
<property name="serverAddress" value="127.0.0.1" />
</resources>
<security>
<all-permissions/>
</security>
<application-desc main-class="test.WSTest"/>
As i said, the whole thing works when run as a normal java application as well as with web start, with the difference that the remote reference lookup takes about 15 seconds with web start.
Can anyone tell me how i could go about this?Meanwhile, i tried the same thing at home on my xp machine (i use vista at work), and even though my test at home basically does the same thing (invoking a simple remote method that just returns "hello world") it worked pretty fast, contary to the 15 second hang on vista.
So i can't really say where the problem is...
I also found these two rmi properties
sun.rmi.transport.connectionTimeout (1.1.6 and later)
The value of this property represents the period (in milliseconds) for which socket connections may reside in an "unused" state, before the Java RMI runtime will allow those connections to be freed (closed). The default value is 15000 milliseconds (15 seconds).
and
sun.rmi.transport.proxy.connectTimeout (1.1 and later)
The value of this property represents the maximum length of time (in milliseconds) that the Java RMI runtime will wait for a connection attempt (createSocket) to complete, before attempting to contact the server using HTTP. This property is only used when the http.proxyHost property is set and the value of java.rmi.server.disableHttp is false. The default value is 15000 milliseconds (15 seconds).
Hoping it would help (totally clueless) i tried to set these as system properties via System.setProperty(...) to a lower value (if that even works this was - please correct me if i am totally wrong here) but it didn't help. -
32-bit JMX/RMI Remote Connection to 64-bit
I am trying to connect to the standard JDK5 JMX server running on RedHat 64-bit Linux from a 32-bit Windows box and continually get Connection refused. Both are running JDK 1.5.0_05, 64-bit version on Linux, 32-bit version on Windows.
Is there a problem connecting between 64-bit and 32-bit OSes? I don't understand "connection refused" if that is the problem.
There is no NAT and no firewall. I am able to connect to other Java services on that box, just not the JMX server. I can browse the RMI Registry on that machine (using the RMI Explorer plug-in from IDEA) but when I try to execute any of the methods I get Connection refused: connect at java.net.PlainSocketImpl.socketConnect. I know I'm connecting to the standard JMX registry because I can see the jmxrmi registry object with methods getVersion() and newClient(). I get the exception when I try to execute, say, the getVersion() method.
JConsole is also not able to connect remotely.
I am, however, able to connect from code running locally on the Linux box. But I am not able to connect from code running on the Windows client through an SSH tunnel.
It appears that 64-bit and 32-bit JVMs cannot communicate over RMI, but is there another explanation?
RobertI have the same problem using jmx through a ssh-tunnel.
Neither programmatically by JMXConnector nor with jconsole it is possible to connect. It seems that the initial request works but then some kind of redirect forces a connect to the endpoint which is not possible at the other side of the tunnel. Instead it should use the local tunnel-port.
So I get "connection refused" for an ip-address that is surely not available from my desktop.
I found several similar problem-descriptions in different newsgroups but no answers how to solve it. -
Spring RMI Remoting Maven Build ClassCast Execption
e have used spring remoting using RMI feature, where the service and client are deployed on same weblogic server. I am using JndiRmiServiceExporter and JndiRmiProxyFactoryBean. It works fine if i deploy the applications through weblogic workshop. But it fails at runtime when a maven build is done and deployed throwing an error
org.springframework.remoting.RemoteLookupFailureException: Could not narrow RMI stub to service interface [xxx.xxIntf]; nested exception is java.lang.ClassCastException: Cannot narrow remote object ClusterableRemoteRef(1683913221122928763S::production_domain:AdminServer [1683913221122928763S::production_domain:AdminServer/416])/416 to xxxx.xxIntf
Client applicationContext xml entries
<bean class="org.springframework.remoting.rmi.JndiRmiServiceExporter">
<property name="service" value="xxxxImpl"/>
<property name="jndiName" value="jndiName"/>
<property name="serviceInterface" value="xxxxIntf"/>
</bean>
Server applicationContext xml entries
<bean id="bean-id" class="org.springframework.remoting.rmi.JndiRmiProxyFactoryBean">
<property name="jndiName" value="jndiName"/>
<property name="jndiEnvironment">
<props>
<prop key="java.naming.factory.url.pkgs">weblogic.jndi.factories</prop>
</props>
</property>
<property name="serviceInterface" value="xxxxxIntf"/>
<property name="refreshStubOnConnectFailure"><value>true</value></property>
<property name="lookupStubOnStartup"><value>false</value></property>
</bean>
Does anything has to be included when a maven build is done.Hi
I have a similar issue with ant. I try to do a remote lookup via an custom built ant task, but it fails at runtime with the same exception that you got.
Did you found any solution?
regards
Kalle -
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]Copyright © 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;
} -
RMI and Threads: Calling wait() on a remote object
I created a counter as a remote object.
Multiple clients are displaying the counter value.
If one of the clients increments the counter, I want the displayed counter value on every client to be updated to the new value (of the counter on the server).
Therefore every client starts a new thread to "listen" for changes of the countervalue. I wanted to call the wait() method on the remote object (the remote counter). But i think it will be called on the stub instead of on the actual remote object.
Therefore i created a extra method waitForChange() on the remote object.
public void waitForChange() throws RemoteException, InterruptedException {
synchronized(this) {
wait();
This method only calls the wait() method. Now I'm sure it's called on the remote object and not on the stub.
This works, but my question is: is there a better way to do this?
Code:
==========================================
The remote interface
==========================================
import java.rmi.Remote;
import java.rmi.RemoteException;
public interface RemoteCounter extends Remote {
void incrementCounter() throws RemoteException;
int getCounterValue() throws RemoteException;
void waitForChange() throws RemoteException, InterruptedException;
} ==========================================
The implementation of the remote interface
==========================================
import java.rmi.*;
import java.rmi.activation.*;
import RemoteCounter;
public class RemoteCounterImpl extends Activatable
implements RemoteCounter {
private static final long serialVersionUID = 1L;
private int counter = 0;
protected RemoteCounterImpl(ActivationID id, MarshalledObject data) throws RemoteException {
super(id, 0);
public void incrementCounter() throws RemoteException {
synchronized(this) {
counter++;
notifyAll(); //Inform all clients of the new countervalue;
public void waitForChange() throws RemoteException, InterruptedException {
synchronized(this) {
wait();
public int getCounterValue() throws RemoteException {
return counter;
}==========================================
A piece of code registering the remote object
==========================================
ActivationDesc desc = new ActivationDesc(agi, "RemoteCounterImpl", codebase, data);
//Register with rmid
RemoteCounter counter = (RemoteCounter)Activatable.register(desc);
// Bind the stub to a name in the registry running on 1099
Naming.bind("Counter", counter);==========================================
The panel containing a button, a label
which starts a new thread listening for
counter value changes
==========================================
import javax.swing.*;
import java.awt.Dimension;
import java.awt.event.*;
import java.rmi.*;
import org.personal.exam.services.RemoteCounter;
public class PanelCounter extends JPanel {
private static final long serialVersionUID = 1L;
JLabel labelX = new JLabel("Press testbutton");
Thread t;
RemoteCounter remoteCounter;
public PanelCounter() {
try {
jbInit();
} catch(Exception e) {
e.printStackTrace();
private void jbInit() throws Exception
this.setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
this.setPreferredSize(new Dimension(450,300));
// The securityManager is required to make is possible
// to download classes from the server
if (System.getSecurityManager() == null) {
System.setSecurityManager(new RMISecurityManager());
//Create a testButton to increment the counter
JButton testButton = new JButton("Increment");
testButton.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent arg0) {
incrementCounter();
this.add(testButton);
//Add a label to display the counter value
this.add(labelX);
// Create thread to listen for counter value changes
try {
remoteCounter = (RemoteCounter)Naming.lookup("Counter");
CounterValueChecker cvl = new CounterValueChecker(labelX, remoteCounter);
//Start a thread to listen for changes of the countervalue
t = new Thread(cvl);
t.start();
} catch(Exception e) {
e.printStackTrace();
this.setVisible(true);
private void incrementCounter() {
String message = "error";
try {
remoteCounter.incrementCounter();
message = "Current value is " + remoteCounter.getCounterValue();
} catch(Exception e) {
System.out.println("Test Exception: " + e.getMessage());
e.printStackTrace();
labelX.setText(message);
}==========================================
The runnable implementation used by the
thread to wait for counterchanges
==========================================
import java.rmi.RemoteException;
import javax.swing.JLabel;
import org.apache.log4j.Logger;
import RemoteCounter;
public class CounterValueChecker implements Runnable {
private JLabel counterLabel;
private RemoteCounter remoteCounter;
public boolean keepChecking= true;
private Logger logger = Logger.getLogger(this.getClass());
public CounterValueChecker(JLabel counterLabel, RemoteCounter remoteCounter){
this.counterLabel = counterLabel;
this.remoteCounter = remoteCounter;
public void run() {
while(keepChecking) {
int newVal = -1;
synchronized(remoteCounter) {
try {
//remoteCounter.wait();
//this does not work. I think because the wait() method is called on the
//stub instead of on the actual remote object
remoteCounter.waitForChange();
} catch (InterruptedException e) {
keepChecking = false;
break;
} catch (RemoteException re) {
re.printStackTrace();
try {
newVal = remoteCounter.getCounterValue();
} catch (RemoteException re) {
re.printStackTrace();
counterLabel.setText("New value: " + newVal);
}This is just a little test. Actually I want to notify clients of changes in data displayed in a Table. If one client saves one record of the data, i want the new record to be displayed immediatly on all clients that are viewing the same data.I've been doing some reading about RMI and callback.
As I understand it, there's a remote object is running on the client now as wel. And the server makes a call to the client.
But now the server makes a call to one client.
And the point is, I want all clients to be updated with the new value.
Does this mean, I have to keep a list with references to all clients connected to the server?
I my code the notifyAll() method causes all waiting Threads (running on several clients) to wake up and do something (getting the new counter value). -
Problems using RMI between linux and windows.
I have problems using RMI between linux and windows.
This is my scenario:
- Server running on linux pc
- Clients running on linux and windows PCs
When a linux client disconnect, first time that server try to call a method of this client, a rmi.ConnectException is generated so server can catch it, mark the client as disconnected and won't communicate with it anymore.
When a windows client (tested on XP and Vista) disconnect, no exceptions are generated (I tryed to catch all the rmi exception), so server cannot know that client is disconnected and hangs trying to communicate with the windows client.
Any ideas?
Thanks in advance.
cambieriThanks for your reply.
Yes, we are implementing a sort of callback using Publisher (remote Observable) and Subscribers (remote Observer). The pattern and relative code is very well described at this link: http://www2.sys-con.com/ITSG/virtualcd/java/archives/0210/schwell/index.html (look at the notifySubscribers(Object pub, Object code) function).
Everything works great, the only problem is this: when a Publisher that reside on a Linux server try to notify something to a "dead" Subscriber that reside on a Windows PC it does't receive the usual ConnectException and so tends to hang.
As a workaround we have solved now starting a new Thread for each update (notification), so only that Thread is blocked (until the timeout i guess) and not the entire "notifySubscribers" function (that contact all the Subscribers).
Beside this, using the Thread seem to give us better performance.
Is that missed ConnectException a bug? Or we are just making some mistake?
We are using java 6 and when both client and server are Linux or Windows the ConnectException always happen and we don't have any problem.
I hope that now this information are enough.
Thanks again and greetings.
O.C. -
Remote object trying to return another remote object and a ClassCastExcepti
I have a server running with a TreeModel (the tree model implements Remote). I also have the the TreeNodes all linked together on the server. Now, I can get to the TreeModel on the server and the root node of the remote tree model.
treeModelStub = (treeModelIface)Naming.lookup(url+"remoteTM"); //works
rootStub = (remoteTreeNodeIface)treeModelStub.getRoot(); //works. The call to getRoot returns Object
But when I call
remoteTreeNodeIface aChild = (remoteTreeNodeIface)rootStub.getChildAt(index) //Does not work. "Exception in thread "main" java.lang.ClassCastException
at remoteTreeNode_Stub.getChildAt(Unknown Source)
The remote tree node method getChildAt returns TreeNode because the class implements TreeNode:
public class remoteTreeNode extends UnicastRemoteObject implements rdcaDataIface, Comparable, TreeNode {
public TreeNode getChildAt(int idx) {
System.out.println("DEBUG: class is "+this.getClass()); // class is remoteTreeNode
return (remoteTreeNode)children.get(idx);
The remote interface is defined as:
public interface rdcaDataIface extends java.rmi.Remote {
public TreeNode getChildAt(int idx) throws RemoteException;
Any ideas why this does not work. Why can a remote object of type Object be returned just fine, but a TreeNode not be returned?
Thank you for your help,
BrentI have a server running with a TreeModel (the tree
model implements Remote). I also have the the
TreeNodes all linked together on the server. Now, I
can get to the TreeModel on the server and the root
node of the remote tree model.
treeModelStub =
(treeModelIface)Naming.lookup(url+"remoteTM");
//works
rootStub =
(remoteTreeNodeIface)treeModelStub.getRoot();
//works. The call to getRoot returns Object
But when I call
remoteTreeNodeIface aChild =
(remoteTreeNodeIface)rootStub.getChildAt(index)******************************************
can only be casted to rdcaDataIface. The returned object is an instanceof the rdcaDataIface_stub, which have nothing to do with TreeNode.
//Does not work. "Exception in thread "main"
java.lang.ClassCastException
at remoteTreeNode_Stub.getChildAt(Unknown
t(Unknown Source)
The remote tree node method getChildAt returns
TreeNode because the class implements TreeNode:
public class remoteTreeNode extends
UnicastRemoteObject implements rdcaDataIface,
Comparable, TreeNode {
public TreeNode getChildAt(int idx) {
System.out.println("DEBUG: class is
lass is "+this.getClass()); // class is
remoteTreeNode
return (remoteTreeNode)children.get(idx);
The remote interface is defined as:
public interface rdcaDataIface extends java.rmi.Remote
public TreeNode getChildAt(int idx) throws
ows RemoteException;
Any ideas why this does not work. Why can a remote
object of type Object be returned just fine, but a
TreeNode not be returned?
Thank you for your help,
Brent -
Conflict between socket and RMI
Hi
I wrote a program in client-server using socket and it was fine. I also wrote a client-server program using RMI. Fine as well. But after I connected the client-server using socket (open socket, send-receive messages, close socket), then use RMI. I got java.rmi.NotBoundException.
Would anyone have a look and provide your feedback please? Thanks.
big J
*****************this is Server.java ***************************
package single;
import java.io.*;
import java.rmi.Naming;
import java.rmi.RemoteException;
import java.net.*;
import java.rmi.*;
public class Server
extends Thread {
public static final int SOCKETPORT = 5555;
private String serverName;
public Server() throws IOException {
System.out.println("*** socket opened ***");
serverName = new String("localhost");
ServerSocket serverSocket = new ServerSocket(SOCKETPORT);
Socket socket = serverSocket.accept();
InputStream is = socket.getInputStream();
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(is));
System.out.println(bufferedReader.readLine());
OutputStream os = socket.getOutputStream();
PrintWriter printWriter = new PrintWriter(new OutputStreamWriter(os), true);
printWriter.println("from server");
os.close();
is.close();
socket.close();
System.out.println("*** socket closed ***");
public void runServer() {
System.out.println("*** start of run():RMI ***");
System.setSecurityManager(new SecurityManager());
try {
RMIInterfaceImpl rMIInterfaceImpl = new RMIInterfaceImpl();
Naming.bind("//" + serverName + ":9999/RMIInterface", rMIInterfaceImpl);
catch (RemoteException ex) {
catch (MalformedURLException ex) {
catch (AlreadyBoundException ex) {
System.out.println("*** end of run():RMI ***");
public static void main(String args[]) throws Exception {
Server server = new Server();
server.runServer();
******************this is Client.java **************************
package single;
import java.io.*;
import java.net.*;
import java.rmi.Naming;
public class Client {
private String serverName;
private final static int SOCKETPORT = 5555;
public Client() throws IOException {
serverName = new String("localhost");
Socket socket = new Socket(serverName, SOCKETPORT);
OutputStream os = socket.getOutputStream();
PrintWriter printWriter=new PrintWriter(os, true);
printWriter.println("from client");
InputStream is = socket.getInputStream();
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(is));
System.out.println(bufferedReader.readLine());
is.close();
os.close();
socket.close();
public void runClient() throws Exception {
System.out.println("*** start of runClient():RMI ***");
System.setSecurityManager(new SecurityManager());
RMIInterface rMIInterfaceImpl = (RMIInterface) Naming.lookup(
"//" + serverName + ":9999/RMIInterface");
String str = rMIInterfaceImpl.print();
System.out.println(str);
rMIInterfaceImpl.serverSide();
System.out.println("*** end of runClient():RMI ***");
public static void main(String args[]) throws Exception {
Client client = new Client();
client.runClient();
***************** this is RMIInterface.java ***********************
package single;
import java.rmi.Remote;
import java.rmi.RemoteException;
interface RMIInterface
extends Remote {
String print() throws RemoteException;
void serverSide() throws RemoteException;
********************* this is RMIInterfaceImpl.java ***************
package single;
import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;
public class RMIInterfaceImpl
extends UnicastRemoteObject
implements RMIInterface {
public RMIInterfaceImpl() throws RemoteException {}
public String print() {
return new String("hello world");
public void serverSide(){
System.out.println("this should appear in serverside");I think you have a timing problem between your client and server. As soon as your client and server programs have finished their socket communication, they will both do their "runServer"/"runClient" methods. If the client attempts to lookup the server before the server has registered itself via Naming.bind(), I would expect that's why you're getting a NotBoundException in the client.
You probably wouldn't use the design of your test client/server for something significant, but a quick and dirty way to make this work might be to have the client call Thread.sleep() for a few seconds before trying to do the lookup.
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