I have a problem with JAVA RMI.
I have a java ee application running, which uses rmi to call specific methods, which have to be implemented specificly for each customer. The vendor gave me an example RMI interface implementation to show how to get a specific hostinterface running. The original codefragment looked like posted example1. The Interface is running but every 2 to 3 days it stops working, without any known reason. The interfaces' log looks like it would be still running. The glassfish server, which calls the interface, shows log entries like this:
[#|2015-10-01T16:27:53.446+0200|SEVERE|glassfish3.1.2|javax.enterprise.system.std.com.sun.enterprise.server.logging|_ThreadID=106;_ThreadName=Thread-2;|egatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) ...
The application error log shows entries like this:
2015-10-05 08:44:07,819 [http-thread-pool-8080(4)] ERROR medexter.arden.server.engine.DelegatingHostInterface - The method evaluateRead on remote interface does not work correctly. java.rmi.NoSuchObjectException: no such object in table at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(Unknown Source) ...
I found several threads like this one: java.rmi.NoSuchObjectException: no such object in table
which tells me the garbage-collection could be responsible and the registry has to be kept statically to prevent the GC from destroying the object. Meanwhile I tried out diffrent ways. My last one (which somehow shows my desparation - restarting the interface every 24h should not be the golden solution) is posted in example2. At the moment I generate an executable jar file and start it as an application. I wanted to get it running as a service later on, but first it should work without any mistakes.
Does anybody hava an idea, what the reason for the described behaviour could be? Any imporovement of the given code apprechiated. I just want to get this stuff working, without loosing connection every few days.
Thank you very much, Martin
Example 1:
import java.rmi.AlreadyBoundException;
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
import java.rmi.server.UnicastRemoteObject;
public class SampleRMIProvider {
private static RmiRegistryThread thr;
public static void main(String[] args) {
SampleRMIProvider prv = new SampleRMIProvider();
prv.init();
}
public void init(){
SampleRMIProvider.thr = new RmiRegistryThread();
thr.start();
}
public class RmiRegistryThread extends Thread {
public boolean run = true;
@Override
public void run() {
System.err.println("thread start");
String name = "RMIHostInterface";
int servicePorti = Integer.parseInt("18989");
try {
RmiHostInterface engine = new RmiHostInterfaceImpl();
RmiHostInterface stub = (RmiHostInterface) UnicastRemoteObject.exportObject(engine, 0);
Registry registry;
try {
registry = LocateRegistry.createRegistry(servicePorti);
} catch (RemoteException e) {
registry = LocateRegistry.getRegistry(servicePorti);
}
registry.bind(name, stub);
} catch (RemoteException e) {
e.printStackTrace();
} catch (AlreadyBoundException e) {
e.printStackTrace();
}
try {
while (this.run) {
Thread.sleep(10000);
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
Example 2:
import java.rmi.AlreadyBoundException;
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
import java.rmi.server.UnicastRemoteObject;
public class SampleRMIProvider extends Thread{
private static Registry r = null;
@Override
public void run() {
String name = "RMIHostInterface";
int servicePorti = Integer.parseInt("20002"); //18989
try {
RmiHostInterface engine = new SampleInterfaceImpl();
RmiHostInterface stub = (RmiHostInterface) UnicastRemoteObject.exportObject(engine, 0);
try {
SampleRMIProvider.r = LocateRegistry.createRegistry(servicePorti);
} catch (RemoteException e) {
SampleRMIProvider.r = LocateRegistry.getRegistry(servicePorti);
}
SampleRMIProvider.r.bind(name, stub);
} catch (RemoteException e) {
e.printStackTrace();
} catch (AlreadyBoundException e) {
e.printStackTrace();
}
System.err.println("RMI Interface created...");
try{
while(true){
Thread.sleep(10000);
}
}
catch (InterruptedException e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
try {
while (true) {
//RMI Interface instanzieren
SampleRMIProvider provider = new SampleRMIProvider();
provider.start();
//Ein Tag pause
Thread.sleep(86400000);
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
14.10.2015 Finally - this minimal example shows a solution that worked for me. Thanks for the useful advices.
import java.rmi.AlreadyBoundException;
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
import java.rmi.server.UnicastRemoteObject;
public class SampleRMIProvider{
private static Registry r = null;
private static SampleHostInterfaceImpl hif = null;
private static RmiHostInterface stub = null;
SampleRMIProvider(){
try{
SampleRMIProvider.r.bind("RMIHostInterface", SampleRMIProvider.stub);
}
catch(RemoteException | AlreadyBoundException e){
e.printStackTrace();
}
}
public static void main(String[] args) {
//setup static references to prevent from beeing collected by GC
try {
SampleRMIProvider.hif = new SampleHostInterfaceImpl();
SampleRMIProvider.stub = (RmiHostInterface) UnicastRemoteObject.exportObject(SampleRMIProvider.hif, 0);
try {
SampleRMIProvider.r = LocateRegistry.createRegistry(20002);
} catch (RemoteException e) {
SampleRMIProvider.r = LocateRegistry.getRegistry(20002);
}
} catch (RemoteException e) {
e.printStackTrace();
}
new SampleRMIProvider();
}
}
