We Keep Coding

RMI - Unmarshalled Exception

I can't seem to get this working. I'm just look at it for basic instruction for a lab, but I've no experience with RMI at all. I can't seem to get why I'm getting the error.
Server
public static void runServer() {
// Install security manager, if none is present
if (System.getSecurityManager() == null) {
System.setSecurityManager(new SecurityManager());
}
try {
Registry registry = LocateRegistry.getRegistry();
System.out.println("Reg: " + registry.toString());
String name = "Server";
Server server = new Server();
I_Server stub = (I_Server) UnicastRemoteObject.exportObject(server, 0);
registry.rebind(name, stub);
System.out.println("All is well :-)\n");
} catch (RemoteException re) {
System.err.println("Remote Exception in DisplayGetEngine.main()\n");
re.printStackTrace();
}
}
}
I have the following run commands and arguments in NetBeans
Arguments: -cp C:\rmi\Server\src;C:\rmi\Server\dist\Server.jar -Djava.rmi.server.codebase=file:/C:/rmi/Server/dist/Server.jar
Working Directory: C:\rmi\Server
My stacktrace is, at the rebind method.
Reg: RegistryImpl_Stub[UnicastRef [liveRef: [endpoint:[10.50.18.205:1099](remote),objID:[0:0:0, 0]]]]
Remote Exception in DisplayGetEngine.main()
java.rmi.ServerException: RemoteException occurred in server thread; nested exception is:
java.rmi.UnmarshalException: error unmarshalling arguments; nested exception is:
java.lang.ClassNotFoundException: server.I_Server
at sun.rmi.server.UnicastServerRef.oldDispatch(UnicastServerRef.java:419)
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:267)
at sun.rmi.transport.Transport$1.run(Transport.java:177)
at sun.rmi.transport.Transport$1.run(Transport.java:174)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:173)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:553)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:808)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:667)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:724)
at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(StreamRemoteCall.java:273)
at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:251)
at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:377)
at sun.rmi.registry.RegistryImpl_Stub.rebind(Unknown Source)
at server.Server.runServer(Server.java:50)
at server.Server.main(Server.java:31)
If I don't run rmiregistry, this is my stacktrace
Remote Exception in DisplayGetEngine.main()
java.rmi.ConnectException: Connection refused to host: 10.50.18.205; nested exception is:
java.net.ConnectException: Connection refused: connect
at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:619)
at sun.rmi.transport.tcp.TCPChannel.createConnection(TCPChannel.java:216)
at sun.rmi.transport.tcp.TCPChannel.newConnection(TCPChannel.java:202)
at sun.rmi.server.UnicastRef.newCall(UnicastRef.java:340)
at sun.rmi.registry.RegistryImpl_Stub.rebind(Unknown Source)
at server.Server.runServer(Server.java:50)
at server.Server.main(Server.java:31)

Try calling createRegistry() first to make sure that you have a running registry. Also, port 0 should be a reserved port so you won't be able to make your server listen on that particular port. Try the default one 1099.

There is no problem in running rmiregistry. If you look into the stacktrace closely,the problem seems to be ClassNotFoundException while the arguments are being unmarshalled in the rmi registry. You will have to check the code base of the RMI server whether server.I_Server class is present in the Server.jar while running it in the classpath.
From RMI FAQs
A.4 Why am I getting a ClassNotFoundException?
Most likely the java.rmi.server.codebase property has not been set (or has not been set correctly) on a VM that is exporting your remote object(s). Please take a look at our tutorial, Dynamic code downloading using Java RMI (Using the java.rmi.server.codebase Property).

The issue was in the build file. I needed to insert this statement.
<target name="startRMI" depends="init">
<exec executable="C:\Program\Files\Java\jdk1.7.0_51\jre\bin\rmiregistry"
dir="${build.classes.dir}"></exec>
</target>

error executing Head First EJB first example

I am following Head First EJB. I know it has EJB 2.0 which is old as now EJB 3.1 is in. But I consider Head first book a good book for learning for amateurs like us.
I am using J2ee 1.3.1 RI and jdk 1.4. I ran the "deploy" tool to deploy by EJB and now I have a ejb client JAVA program given below:
import javax.naming.*;
import java.rmi.*;
import javax.rmi.*;
import headfirst.*;
import javax.ejb.*;
import java.util.*;
public class AdviceClient {
public static void main(String[] args){
new AdviceClient().go();
}
public void go(){
try{
Properties props=new Properties();
props.setProperty(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.rmi.registry.RegistryContextFactory");
//props.setProperty(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.fscontext.RefFSContextFactory");
//env.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.rmi.registry.RegistryContextFactory");
//props.setProperty(Context.INITIAL_CONTEXT_FACTORY,"com.sun.enterprise.naming.SerialInitContextFactory");
props.setProperty(Context.PROVIDER_URL,"rmi://localhost:1050");
//props.setProperty("java.naming.provider.url","rmi://localhost:1099");
Context ic = new InitialContext(props);
Object o = ic.lookup("Advisor");
AdviceHome home = (AdviceHome)PortableRemoteObject.narrow(o,AdviceHome.class);
Advice advisor = home.create();
System.out.println(advisor.getAdvice());
}
catch(Exception ex){
ex.printStackTrace();
}
}
}
Following the book, I compiled the program. The "Properties" part is something not mentioned in the example. I got it from some other examples on the web. Now, that when I am executing the client, am getting the following error:
F:\EJBProject\advice>java -classpath AdviceAppClient.jar;. AdviceClient
javax.naming.CommunicationException [Root exception is java.rmi.ConnectIOException: error during JRMP connection establishment; nested exception is:
java.net.SocketTimeoutException: Read timed out]
at com.sun.jndi.rmi.registry.RegistryContext.lookup(Unknown Source)
at com.sun.jndi.rmi.registry.RegistryContext.lookup(Unknown Source)
at javax.naming.InitialContext.lookup(Unknown Source)
at AdviceClient.go(AdviceClient.java:26)
at AdviceClient.main(AdviceClient.java:11)
Caused by: java.rmi.ConnectIOException: error during JRMP connection establishment; nested exception is:
java.net.SocketTimeoutException: Read timed out
at sun.rmi.transport.tcp.TCPChannel.createConnection(Unknown Source)
at sun.rmi.transport.tcp.TCPChannel.newConnection(Unknown Source)
at sun.rmi.server.UnicastRef.newCall(Unknown Source)
at sun.rmi.registry.RegistryImpl_Stub.lookup(Unknown Source)
... 5 more
Caused by: java.net.SocketTimeoutException: Read timed out
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(Unknown Source)
at java.net.SocketInputStream.read(Unknown Source)
at java.io.BufferedInputStream.fill(Unknown Source)
at java.io.BufferedInputStream.read(Unknown Source)
at java.io.DataInputStream.readByte(Unknown Source)
Please help. I am stuck up badly here. I wanted to sit for the OCBCD exam!
Regards,
Shouvanik

Finally Solved.
If you hit a roadblock while running the first EJB example simply follow these steps
to run the first example of HeadFirst EJB.
Softwares
1. j2sdk1.4.1 - jdk
2. j2sdkee1.3.1 - j2ee RI
3. CMD (command prompt)
Compile all the classes using c:\j2sdkee1.3.1\lib\j2ee.jar library.
Now, create a App and deploy EJB inside RI. download the application client as shown in the book.
Now, comes the tricky part.
Compile client class using the following jars
javac -classpath AdviceAppClient.jar;c:\j2sdkee1.3.1\lib\j2ee.jar AdviceClient.java
Next, run the client as follows
java -cp AdviceAppClient.jar;c:\j2sdkee1.3.1\lib\j2ee.jar;c:\j2sdk1.4.1\jre\lib\rt.jar;. AdviceClient

sending sms from pc to mobile

i am using smsj api to send sms from pc to mobile through gsm modem. as given on the page, i have tried the following code.
package org.marre;
import java.io.IOException;
import org.marre.sms.SmsException;
public class SendMessage {
public void send() {
try{
// Send SMS with clickatell
SmsSender smsSender = SmsSender.getGsmSender("COM7");
String msg ="sample message";
// International number to reciever without leading "+"
String reciever = "9561356345";
// Number of sender (not supported on all transports)
String sender ="9561356345";
// Connect
smsSender.connect();
// Send message
smsSender.sendTextSms(msg, reciever, sender);
// Disconnect
smsSender.disconnect();
} catch(IOException i){
i.printStackTrace();
System.out.println("i");
} catch(SmsException s){
s.printStackTrace();
System.out.println("s");
}
}
public static void main(String args[]){
SendMessage app = new SendMessage();
app.send();
}
}
but i am getting this error message:
Exception in thread "main" java.lang.NoClassDefFoundError: org/slf4j/LoggerFactory
at org.marre.sms.transport.gsm.SerialComm.<clinit>(SerialComm.java:58)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Unknown Source)
at org.marre.sms.transport.gsm.GsmTransport.class$(GsmTransport.java:83)
at org.marre.sms.transport.gsm.GsmTransport.<clinit>(GsmTransport.java:83)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Unknown Source)
at org.marre.sms.transport.SmsTransportManager.getTransport(SmsTransportManager.java:75)
at org.marre.SmsSender.<init>(SmsSender.java:112)
at org.marre.SmsSender.getGsmSender(SmsSender.java:180)
at org.marre.SendMessage.send(SendMessage.java:12)
at org.marre.SendMessage.main(SendMessage.java:30)
Caused by: java.lang.ClassNotFoundException: org.slf4j.LoggerFactory
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 12 more
i am a beginner in java. please help me with the code.
note: i have used smslib api earlier for sending a simple text message. but this does not support ems messages. if you have any other library in mind which supports ems messages, please let me know. smsj was one i could easily download.

The real cause of the problem lies here:
Caused by: java.lang.ClassNotFoundException: org.slf4j.LoggerFactory
The compiler couldn't find org.slf4j.LoggerFactory from the classpath.
Download SLF4J and add the library in your classpath and compile your code.
Note: As smsj references a very old version of Slf4J you need to use this old version as well: http://mvnrepository.com/artifact/org.slf4j/slf4j-simple/1.0-beta9

What type of connections "RMI TCP Connection(idle)" threads correspond to?

I'm working on a distributed system which is RMI based using jdk1.6.
Occasionally I can see ConcurrentModificationException errors on that thread happening within the RMI runtime when it fails to serialize objects. I can reproduce that exception easily by concurrently updating object being returned from remote method.
But the problem is that I can't find the source of those calls. RMI exception is written to stderr (captured on server side within runtime code after it exits remote object method), but there are no matching exception in client services (while if that was a legitimate remote call, RemoteException with appropriate cause would be raised).
The only different thing about those exceptions is that they are happening on "RMI TCP Connection(idle)" thread and not on a thread like "RMI TCP Connection(<connection count>)-<client endpoint info>".
Any clues on what are those "idle" threads in RMI? I failed to find such within the openjdk sources.
Upd: I'm adding an exception stack trace as reproduced, which is what you usually see in described situation.
Server side console shows:
Exception dispatching call to [-3534448f:12f54948b7f:-7fff, 349678755005857493] in thread "RMI TCP Connection(6)-x.x.x.x" at Thu Apr 14 16:15:13 BST 2011:
java.util.ConcurrentModificationException
at java.util.ArrayList.writeObject(ArrayList.java:573)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:945)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1469)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1400)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1158)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:330)
at sun.rmi.server.UnicastRef.marshalValue(UnicastRef.java:274)
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:315)
at sun.rmi.transport.Transport$1.run(Transport.java:159)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:155)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:535)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:790)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:649)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)
Client size exception thrown to caller:
java.rmi.UnmarshalException: error unmarshalling return; nested exception is:
java.io.EOFException
at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:173)
at java.rmi.server.RemoteObjectInvocationHandler.invokeRemoteMethod(RemoteObjectInvocationHandler.java:178)
at java.rmi.server.RemoteObjectInvocationHandler.invoke(RemoteObjectInvocationHandler.java:132)
at $Proxy0.getData(Unknown Source)
at Clnt.main(Clnt.java:11)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:115)
Caused by: java.io.EOFException
at java.io.ObjectInputStream$BlockDataInputStream.peekByte(ObjectInputStream.java:2553)
at java.io.ObjectInputStream.skipCustomData(ObjectInputStream.java:1899)
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1873)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1752)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1328)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:350)
at sun.rmi.server.UnicastRef.unmarshalValue(UnicastRef.java:306)
at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:155)
... 9 more

Threads are created in RMI's connection pool with the name 'RMI TCP Connection(idle)'. When one of these is used, the runnable it is being used to execute renames the thread to 'RMI TCP Connection(n)' where n is the connection number being handled (a sequential number), and renames back to 'idle' in the runnable's finally block. So any trace labelled 'RMI TCP Connection(idle)' must come before the runnable renames it as a connection thread, or after it has been renamed back.
Don't ask me how that is possible. The actual answer to your problem, if not your question, is not to modify objects while they are concurrently being returned ;-)

I got to the bottom of it. Problem happens in two cases:
When marshaling a return value throws some exception and that exception in turn contains an object prone to concurrent modification. UnicastServerRef tries to write the cause into the (already corrupted) return stream and causes ConcurrentModificationException.
When method raises an exception and this exception fails to serialize with ConcurrentModificationException (or any other runtime exception).
This exception goes all the way up the stack and is caught and logged by thread pool, not RMI runtime (that's why there is no Exception dispatching call to line at the beginning). That explains thread name being idle since it is already returned to pool from RMI's point of view.
Here's the real exception which is in fact a bit different from what reproduced exception shows in terms of first line and actual call trace:
Exception in thread "RMI TCP Connection(idle)" java.util.ConcurrentModificationException
at java.util.ArrayList.writeObject(ArrayList.java:573)
at sun.reflect.GeneratedMethodAccessor6.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:945)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1461)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1392)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1150)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1509)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1474)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1392)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1150)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1509)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1474)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1392)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1150)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1509)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1474)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1392)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1150)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:326)
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:343)
at sun.rmi.transport.Transport$1.run(Transport.java:159)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:155)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:535)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:790)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:649)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:619)
It doesn't give much clues to the original problem, so I'll have to wait for a client exception to show up at some point to fix that.
If that kind of exception happens when reading JMX attribute by jconsole, it'll not show stacktrace, but will show attribute value as Unavailable.

java RMI - unexpected error

I have been working on to create a sample RMI project for a while and having difficulty with the following error for a few hours now. If anyone of you can point me towards my mistake, I will be grateful. I will be posting the trimmed code with the error.
Thanks in advance for your time.
PrimeFinder.java
import //irrelevant
public interface PrimeFinder extends Remote
{
public List<Integer> findPrime (int startPoint, int endPoint )
throws RemoteException;
}
PrimeFinderService.java
import //irrelevant
public class PrimeFinderService extends UnicastRemoteObject
implements PrimeFinder
{
public PrimeFinderService () throws RemoteException
{
super();
}
public List<Integer> findPrime(int startPoint, int endPoint)
throws RemoteException {
// Irrelevant
}
public static void main ( String args[] ) throws Exception
{
if (System.getSecurityManager() == null)
System.setSecurityManager ( new RMISecurityManager() );
PrimeFinderService svr = new PrimeFinderService();
Naming.bind ("PowerService", svr);
System.out.println ("Service bound....");
}
}
.policy
grant {
permission java.security.AllPermission; }
The error that is killing me :
Exception in thread "main" java.rmi.ServerException: RemoteException occurred in server thread; nested exception is:
java.rmi.UnmarshalException: error unmarshalling arguments; nested exception is:
java.lang.ClassNotFoundException: access to class loader denied
at sun.rmi.server.UnicastServerRef.oldDispatch(UnicastServerRef.java:419)
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:267)
at sun.rmi.transport.Transport$1.run(Transport.java:177)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:173)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:553)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:808)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:667)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:679)
at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(StreamRemoteCall.java:273)
at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:251)
at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:377)
at sun.rmi.registry.RegistryImpl_Stub.bind(Unknown Source)
at java.rmi.Naming.bind(Naming.java:128)
at q7.PrimeFinderService.main(PrimeFinderService.java:69)
Caused by: java.rmi.UnmarshalException: error unmarshalling arguments; nested exception is:
java.lang.ClassNotFoundException: access to class loader denied
at sun.rmi.registry.RegistryImpl_Skel.dispatch(Unknown Source)
at sun.rmi.server.UnicastServerRef.oldDispatch(UnicastServerRef.java:409)
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:267)
at sun.rmi.transport.Transport$1.run(Transport.java:177)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:173)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:553)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:808)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:667)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:679)
Caused by: java.lang.ClassNotFoundException: access to class loader denied
at sun.rmi.server.LoaderHandler.loadClass(LoaderHandler.java:445)
at sun.rmi.server.LoaderHandler.loadClass(LoaderHandler.java:182)
at java.rmi.server.RMIClassLoader$2.loadClass(RMIClassLoader.java:637)
at java.rmi.server.RMIClassLoader.loadClass(RMIClassLoader.java:264)
at sun.rmi.server.MarshalInputStream.resolveClass(MarshalInputStream.java:214)
at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1592)
at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1513)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1749)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1346)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:368)
... 12 more
Caused by: java.security.AccessControlException: access denied (java.io.FilePermission /home/cem/workspace/OBSS_q7/bin/q7/- read)
at java.security.AccessControlContext.checkPermission(AccessControlContext.java:393)
at java.security.AccessController.checkPermission(AccessController.java:553)
at java.lang.SecurityManager.checkPermission(SecurityManager.java:549)
at sun.rmi.server.LoaderHandler$Loader.checkPermissions(LoaderHandler.java:1173)
at sun.rmi.server.LoaderHandler$Loader.access$000(LoaderHandler.java:1127)
at sun.rmi.server.LoaderHandler.loadClass(LoaderHandler.java:409)
... 21 more
Edit 1:
The error line that I'm trying to overcome is:
Caused by: java.security.AccessControlException: access denied (java.io.FilePermission /home/cem/workspace/OBSS_q7/bin/q7/- read)
I have tried at least 10 different approaches in my .policy file - all of which ended up with the same problem. I have tried anything in the tutorials I have found and it's I believe safe to say that the problem doesn't lie in .policy file.
I have also meddled with the codebase, giving the codebase wrong ends up with different errors so that can't be it either.
Still looking for ideas ^^
Cheers !

Get rid of the SecurityManager, or else write yourself a security policy file that grants that permission.

The problem was regarding linux file system permissions, altering permissions fixes the problem.

If someone stumbles upon the issue on Windows, then two words... Windows Defender. It probably just deleted your project files.
So just rebuild your project. No not "build", just entirely "rebuild".
Windows Defender might delete your project' executables if they went into high CPU usage. So I also always suggest putting your project' directory as an exception.