I'm trying to built java rmi to calculate greatest common divisor.In my server file it's indicate error in below line.
Registry reg=new LocateRegistry.createRegistry(1099)
here with my server file code
import java.rmi.*;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
public class gcdServer {
public static void main(String args[]){
try{
Registry reg=new LocateRegistry.createRegistry(1099);
}catch(Exception e){
e.printStackTrace();
}
}
}
LocateRegistry constructor is private, you cannot create instance on it. You need to call the static method createRegistry like so.,
Registry reg = LocateRegistry.createRegistry(1099);
Related
I am learning RMI concepts and had built a simple program taking reference from head first java. All Went fine the first time i ran the code through command prompt.
the next time I ran code the command:
rmiregistry
took too long to load and nothing happened.
I even tried the solution in this thread but nothing happend.
need help to run RMI Registry
also when i run my server and client file i get this error:
Exception: java.rmi.ConnectException: Connection refused to host: 192.168.1.105; nested exception is:
java.net.ConnectException: Connection refused: connect
My Source Code:
myremote.java
import java.rmi.*;
public interface myremote extends Remote
{
public String sayhello() throws RemoteException;
}
Server.java
import java.rmi.*;
import java.rmi.server.*;
public class Server extends UnicastRemoteObject implements myremote
{
public Server() throws RemoteException{}
public String sayhello()
{
return("Server says hi");
}
public static void main(String args[])
{
try
{
myremote S = new Server();
Naming.rebind("remotehello",S);
}
catch(Exception E)
{
System.out.println("Exception: "+E);
}
}
}
client.java
import java.rmi.*;
public class client
{
public static void main(String[] args)
{
client c = new client();
c.go();
}
public void go()
{
try
{
myremote S=(myremote) Naming.lookup("rmi://127.0.0.1/remotehello");
System.out.println("Output:"+S.sayhello());
}
catch(Exception E)
{
System.out.println("Exception: "+ E);
}
}
}
Can't run RMI registry on my system
You've provided no evidence of that.
took too long to load
I don't know what this means. Evidence?
nothing happened.
Nothing is supposed to happen. The RMI registry doesn't print anything. It just sits there.
Run it and try again. You'll be surprised.
I would like to access an existing RMI server. I do not have access to its source code, so I would like to set up a client that calls an existing service in the RMI Server.
What is the best way to create a client to invoke a particular method and can RMI be converted to a webservice?
Below is the class I have created:
package server;
import com.SerialService;
import java.rmi.Naming;
public class NewClass {
public static void main(String args[]) {
//SerialService obj = null;
try {
SerialService obj = (SerialService) Naming.lookup("//localhost:8083/");
System.out.println(obj.getSerial());
} catch (Exception e) {
e.printStackTrace();
}
}
}
You will need to get the RMI services client stub so you can call/compile against. You would still need to know the port that the service is listening on.
import java.rmi.Naming;
public class RmiClient {
public static void main(String args[]) throws Exception {
RmiServerIntf obj = (RmiServerIntf)Naming.lookup("//localhost/RmiServer");
System.out.println(obj.getMessage());
}
}
I am learning RMI by myself now.I put all my files in the same directory and they are working well.But after I separate the server and client in different directory,there will be an error said
RemoteException
java.rmi.UnmarshalException: error unmarshalling return; nested exception is:
java.lang.ClassNotFoundException: CalculatorImpl_Stub (no security manager: RMI class loader disabled).
I dont know how to fix it.and here is my code :
Server
import java.rmi.Naming;
public class CalculatorServer{
public CalculatorServer(){
try{
Calculator c = new CalculatorImpl();
Naming.rebind("rmi://localhost:1099/CalculatorService", c);
}catch(Exception e){
System.out.println("Trouble: "+ e);
}
}
public static void main(String args[]){
new CalculatorServer();
}
}
Client
import java.rmi.Naming;
import java.rmi.RemoteException;
import java.net.MalformedURLException;
import java.rmi.NotBoundException;
public class CalculatorClient{
public static void main(String[] args){
try{
Calculator c = (Calculator)Naming.lookup("rmi://localhost/CalculatorService");
System.out.println(c.sub(4,3));
System.out.println(c.add(4,5));
System.out.println(c.mul(3,6));
System.out.println(c.div(9,3));
}catch(MalformedURLException murle){
System.out.println();
System.out.println("MalformedURLException");
System.out.println(murle);
}
....
}
You've over-separated. Some of the .class files are common to both the server and the client. The class mentioned in the exception is one of them, and so are any others that show up in subsequent such exceptions.
I am creating RMI program for my class assignment in Netbeans. It is a simple RMI program and The server side is working properly. But as I run my client side file. It ends up giving me error
Exception in thread "main" java.security.AccessControlException: access denied ("java.net.SocketPermission" "127.0.0.1:1099" "connect,resolve")
plus it is saying some error at line 26 at client code.
For clear understanding I am giving full code of all three files.
Interface.java :
package RMI;
import java.rmi.Remote;
import java.rmi.RemoteException;
public interface DemoInterface extends Remote {
public String SayDemo() throws RemoteException;
}
Server.java
package RMI;
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
import java.rmi.server.UnicastRemoteObject;
public class Server implements Interface{
public Server()
{
super();
}
private String message;
public Server(String msg) throws RemoteException
{
message = msg;
}
public static void main(String[] args) {
try {
DemoInterface h = new Server("Hello");
DemoInterface stub = (DemoInterface) UnicastRemoteObject.exportObject(h,0);
LocateRegistry.createRegistry(4096);
Registry registry = LocateRegistry.getRegistry("127.0.0.1",4096);
registry.rebind("Hello", stub);
System.out.println("Server is connected and ready to use");
}
catch(Exception e)
{
System.out.println("server not connected\n"+e);
}
}
#Override
public String SayDemo() throws RemoteException {
System.out.println("Server.saydemo override");
return message;
}
}
Client.java
package RMI;
import java.rmi.NotBoundException;
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
public class Client {
public static void main(String[] args) {
if(System.getSecurityManager() == null)
{
System.setSecurityManager(new SecurityManager());
}
try {
Registry reg = LocateRegistry.getRegistry("127.0.0.1", 4096);
System.out.println("in try after reg locate");
DemoInterface h = (DemoInterface) reg.lookup("Hello");//Error Showed on this line by netbeans
System.out.println(h.SayDemo());
}
catch(RemoteException | NotBoundException e)
{
System.out.println(""+e );
}
}
}
please guide me where I am wrong. Thank You in advance.
You set a SecurityManager in your client main method. Did you also provide a security policy file? The default policy is not very permissive, and denies, among other things, Socket operations.
You can specify a policy that allows all permissions to all code bases like so.
grant {
permission java.security.AllPermission;
};
add it to your command line for invoking java. Substitute mypolicy for your policy file and SomeApp for your main class. Note the two = characters in the second argument
java -Djava.security.manager -Djava.security.policy==mypolicy SomeApp
Note that this is not a safe policy to run for RMI in a production environment (RMI can load remote code bases).
Proper use of the SecurityManager class and policy configuration is a complex topic, for further reading I suggest Java SE 7 Security Documentation and in particular Default Policy Implementation and Policy File Syntax
I get a remote exception when I try to run my RMI example. I cannot understand why.
I run the program without any arguments to the program itself or to the JVM.
Please help me to get rid of the exception.
Thanks very much
This is the exception I get:
Server exception: java.rmi.ServerException: RemoteException occurred in server thread; nested exception is:
java.rmi.UnmarshalException: error unmarshalling arguments; nested exception is:
java.lang.ClassNotFoundException: hello.Hello
java.rmi.ServerException: RemoteException occurred in server thread; nested exception is:
java.rmi.UnmarshalException: error unmarshalling arguments; nested exception is:
java.lang.ClassNotFoundException: hello.Hello
These are the classes I have:
The client class:
package hello;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
public class Client {
private Client() {}
public static void main(String[] args) {
String host = (args.length < 1) ? null : args[0];
try {
Registry registry = LocateRegistry.getRegistry(host);
Hello stub = (Hello) registry.lookup("Hello");
String response = stub.sayHello();
System.out.println("response: " + response);
} catch (Exception e) {
System.err.println("Client exception: " + e.toString());
e.printStackTrace();
}
}
}
The remote interace:
package hello;
import java.rmi.Remote;
import java.rmi.RemoteException;
public interface Hello extends Remote {
String sayHello() throws RemoteException;
}
And finally the server:
package hello;
import java.rmi.registry.Registry;
import java.rmi.registry.LocateRegistry;
import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;
public class Server implements Hello {
public Server() {}
public String sayHello() {
return "Hello, world!";
}
public static void main(String args[]) {
try {
Server obj = new Server();
Hello stub = (Hello) UnicastRemoteObject.exportObject(obj, 0);
// Bind the remote object's stub in the registry
Registry registry = LocateRegistry.getRegistry("localhost");
registry.bind("Hello", stub);
System.err.println("Server ready");
} catch (Exception e) {
System.err.println("Server exception: " + e.toString());
e.printStackTrace();
}
}
}
Either the Registry or the client or both cannot find the class named in the exception. There are several possible solutions:
include that class in the classpath when executing the Registry and the client. And all the classes it depends on, recursively until closure.
Start the Registry from inside the server JVM, with LocateRegistry.createRegistry(), which solves that classpath problem, and provide the necessary classes on the client's classpath only.
Use the codebase feature to ensure all the system components can access the required server-side classes.
As outlined in the RMI trail
You may need to supply the java.rmi.server.codebase parameter that list all the jars that the RMI server needs to export the objects...
See Running the examples and look at the "Starting the server" section. Also be sure to check out the section on running the client program for additional suggested parameters