I was learning rmi and I came up with a problem and I cannot solve it.
Here is the simple code
client code:
package rmi_test;
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) throws RemoteException, NotBoundException
{
Registry registry = LocateRegistry.getRegistry("127.0.0.1");
DNInterface s = (DNInterface) registry.lookup("DNInterface");
if (s.test())
System.out.println("Hello World");
}
}
Interface code:
package rmi_test;
import java.rmi.Remote;
import java.rmi.RemoteException;
public interface DNInterface extends Remote{
public boolean test() throws RemoteException;
}
Server Code:
package rmi_test;
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
import java.rmi.server.UnicastRemoteObject;
public class DataNodeImp implements DNInterface{
#Override
public boolean test() throws RemoteException {
System.out.println("test success");
return true;
}
public DataNodeImp()
{
super();
}
private static void boot() throws RemoteException
{
DNInterface d = new DataNodeImp();
DNInterface stub =
(DNInterface) UnicastRemoteObject.exportObject(d, 0);
Registry registry = LocateRegistry.getRegistry();
registry.rebind("DNInterface", stub);
}
public static void main(String[] args) throws RemoteException
{
String name = "DNInterface";
boot();
}
}
Then I use the following commands to compile the code
javac -cp src: src/rmi_test/DNInterface.java
javac -cp src: src/rmi_test/DataNodeImp.java
javac -cp src: src/rmi_test/client.java
then i type
rmiregistry &
When I try to use
java -cp src: rmi_test.DataNodeImp to run the server
it said
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: rmi_test.DNInterface
Is there anything wrong with the command I run the code?
Why I cannot find DNInterface.class?
Thank you very much!
The Registry doesn't have that class in its CLASSPATH.
The simplest solution is to use LocateRegistry.createRegistry() in the server JVM rather than rmiregistry.
Related
import io.vertx.core.AbstractVerticle;
import io.vertx.core.Vertx;
import io.vertx.ext.web.Router;
public class app extends AbstractVerticle{
#Override
public void start() throws Exception{
Router router = Router.router(vertx);
router.route().handler(routingContext -> {
routingContext.response()
.putHeader("content-type", "text/html")
.end("hello vert.x");
});
vertx.createHttpServer().requestHandler(router::accept).listen(8888);
}
public static void main(String[] args) {
Vertx vertx = Vertx.vertx();
vertx.deployVerticle(new app());
}
}
then error occurs as java.lang.NoSuchMethodError: io.netty.resolver.HostsFileParser.parseSilently()Ljava/util/Map;
Try this way
import io.vertx.core.AbstractVerticle;
import io.vertx.ext.web.Router;
public class Server extends AbstractVerticle {
#Override
public void start() throws Exception {
Router router = Router.router(vertx);
router.route().handler(routingContext -> {
routingContext.response().putHeader("content-type", "text/html").end("hello vert.x");
});
vertx.createHttpServer().requestHandler(router::accept).listen(8080);
}
}
run mvn clean package then java -jar /path/to/jar
Also in java app is not a valid class name.
Class names start with a capital e.g. App
Here is my Program and,
package myapp;
import java.rmi.RemoteException;
import visad.DataImpl;
import visad.VisADException;
import visad.data.hdf5.HDF5Form;
import ncsa.hdf.hdf5lib.*;
public final class hfAdapter2
{
String filePath;
String path;
public hfAdapter2() throws VisADException, RemoteException
{
filePath="F:\\Devanshi\\Input\\xyz.h5";
System.load("F:\\Devanshi\\Projects\\MyApp\\Lib\\jhdf.dll");
System.load("F:\\Devanshi\\Projects\\MyApp\\Lib\\jhdf5.dll");
HDF5Form h=new HDF5Form();
DataImpl ncData=h.open(filePath);
}
public static void main(String[] args)
throws RemoteException, VisADException, IOException
{
new hfAdapter2();
}
}
The exception I got is :
Exception in thread "main" java.lang.UnsatisfiedLinkError:
ncsa.hdf.hdf5lib.H5.H5Fopen(Ljava/lang/String;II)I
at ncsa.hdf.hdf5lib.H5.H5Fopen(Native Method)
at visad.data.hdf5.hdf5objects.HDF5File.<init>(HDF5File.java:85)
at visad.data.hdf5.HDF5FileAdapted.<init>(HDF5FileAdapted.java:70)
at visad.data.hdf5.HDF5Form.open(HDF5Form.java:102)
at myapp.hfAdapter2.<init>(hfAdapter2.java:46)
at myapp.hfAdapter2.main(hfAdapter2.java:96)
I have tried to solve this by
-Dncsa.hdf.hdf5lib.H5.hdf5lib=F:\DLL\hdf5_ij_plugin\lib\win32
-Djava.library.path=F:\DLL\hdf5_ij_plugin\lib\win32
and also this:
-Dncsa.hdf.hdf5lib.H5.hdf5lib=F:\DLL\hdf5_ij_plugin\lib\win32\jhdf5.lib
-Djava.library.path=F:\DLL\hdf5_ij_plugin\lib\win32\jhdf5.lib
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 have written a Java RMI chat application. There are four classes and two interfaces. Here they are:
ChatClient
import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;
import java.util.Scanner;
com.za.tutorial.rmi.server.ChatServerIF;
public class ChatClient extends UnicastRemoteObject implements ChatClientIF,Runnable {
private ChatServerIF chatServer;
private String name = null;
protected ChatClient(String name, ChatServerIF chatServer) throws RemoteException {
this.name = name;
this.chatServer = chatServer;
chatServer.registerChatClient(this);
}
public void retrieveMessage(String message) throws RemoteException {
// TODO Auto-generated method stub
System.out.println(message);
}
public void run() {
Scanner scanner = new Scanner(System.in);
String message;
while(true){
message = scanner.nextLine();
try {
chatServer.broadcastMessage(name + " : " + message);
} catch (RemoteException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
ChatClientDriver
import java.net.MalformedURLException;
import java.rmi.Naming;
import java.rmi.NotBoundException;
import java.rmi.RemoteException;
import com.za.tutorial.rmi.server.ChatServerIF;
public class ChatClientDriver {
public static void main(String[] args) throws MalformedURLException, RemoteException, NotBoundException {
String chatServerURL = "rmi://localhost/RMIChatServer";
ChatServerIF chatServer = (ChatServerIF) Naming.lookup(chatServerURL);
new Thread(new ChatClient(args[0],chatServer)).start();
}
}
ChatClientInterface
import java.rmi.Remote;
import java.rmi.RemoteException;
public interface ChatClientIF extends Remote {
void retrieveMessage(String message) throws RemoteException;
}
ChatServer
import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;
import java.util.ArrayList;
import com.za.tutorial.rmi.client.ChatClientIF;
public class ChatServer extends UnicastRemoteObject implements ChatServerIF {
private ArrayList<ChatClientIF> chatClients;
protected ChatServer() throws RemoteException {
chatClients = new ArrayList<ChatClientIF>();
}
public synchronized void registerChatClient(ChatClientIF chatClient)
throws RemoteException {
this.chatClients.add(chatClient);
}
public synchronized void broadcastMessage(String message) throws RemoteException {
int i = 0;
while(i < chatClients.size()){
chatClients.get(i++).retrieveMessage(message);
}
}
}
ChatServerDriver
import java.net.MalformedURLException;
import java.rmi.Naming;
import java.rmi.RemoteException;
public class ChatServerDriver {
public static void main(String[] args) throws RemoteException, MalformedURLException {
Naming.rebind("RMIChatServer", new ChatServer());
}
}
ChatServerInterface
import java.rmi.Remote;
import java.rmi.RemoteException;
import com.za.tutorial.rmi.client.ChatClientIF;
public interface ChatServerIF extends Remote {
void registerChatClient(ChatClientIF chatClient) throws RemoteException;
void broadcastMessage(String message) throws RemoteException;
}
When I run it on Commando, first of all I run rmic ChatClient and ChatServer, then rmiregistry. Then i run chatServerDriver which works completely fine. after that, when I run chatClientDriver with a name, I get the following error, I dont understand why :/ Can I get any solution for this?
Thanks :)
Exception in thread "main" java.rmi.NotBoundException: RMIChatServer
at sun.rmi.registry.RegistryImpl.lookup(RegistryImpl.java:136)
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 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$ConnectionHandler.run(TCPTransport.java:667)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:722)
at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(Unknown Source)
at sun.rmi.transport.StreamRemoteCall.executeCall(Unknown Source)
at sun.rmi.server.UnicastRef.invoke(Unknown Source)
at sun.rmi.registry.RegistryImpl_Stub.lookup(Unknown Source)
at java.rmi.Naming.lookup(Unknown Source)
at com.za.tutorial.rmi.client.ChatClientDriver.main(ChatClientDriver.java:15)
It also looks like you have a different address in Rebind to what is being used by the client to connect.
Naming.rebind("//localhost/RMIChatServer", new ChatServer());
There's an example implementation on the following Wikipedia page which may be worth comparing against your code.
http://en.wikipedia.org/wiki/Java_remote_method_invocation
Note that using Java 1.5+ you don't need to use rmic anymore see Do we really need to create Stub in java RMI?
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