Java RMI实现

Question

我有一个典型的客户端&服务器场景，我希望客户端能够从服务器上运行的对象调用方法。我使用Java RMI来解决这种情况。

服务器端代码如下，可以很好地编译和运行：

ServerInt.java

package gpio.control;
import java.rmi.Remote;
import java.rmi.RemoteException;

public interface ServerInt extends Remote{
    public void setHeizung(boolean x) throws RemoteException;
    public void quitError() throws RemoteException;
    public void startPWM(int periode,int pulsbreite,int pulsanzahl) throws RemoteException;
}

ServerImpl.java

package gpio.control;
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
import java.rmi.server.RemoteServer;
import java.rmi.server.UnicastRemoteObject;

public class ServerImpl implements ServerInt{
    private Model myModel;

    public ServerImpl(Model m) throws RemoteException {
        myModel = m;

        LocateRegistry.createRegistry(1099);
        ServerInt stub = (ServerInt) UnicastRemoteObject.exportObject(this, 1099);
        RemoteServer.setLog(System.out);

        Registry registry = LocateRegistry.getRegistry();
        registry.rebind("Server1", stub);
    }

    @Override
    public void setHeizung(boolean x) throws RemoteException {
        myModel.setHeizung(x);
    }

    @Override
    public void quitError() throws RemoteException {
        myModel.quitError();
    }

    @Override
    public void startPWM(int periode, int pulsbreite, int pulsanzahl) throws RemoteException {
        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }
}

出于测试目的，我还创建了一个小型客户端应用程序，它与服务器应用程序运行在同一台服务器上：

Client.java

package client;

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();
        ServerInt serverint = (ServerInt) registry.lookup("rmi://127.0.0.1:1099/Server1"); 
        serverint.setHeizung(true);
    }

}

当我现在运行客户端程序时，我得到了以下错误: Error from Client：

Exception in thread "main" java.rmi.NotBoundException: rmi://localhost:1099/Server1
    at sun.rmi.registry.RegistryImpl.lookup(RegistryImpl.java:166)
    at sun.rmi.registry.RegistryImpl_Skel.dispatch(Unknown Source)
    at sun.rmi.server.UnicastServerRef.oldDispatch(UnicastServerRef.java:410)
    at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:268)
    at sun.rmi.transport.Transport$1.run(Transport.java:200)
    at sun.rmi.transport.Transport$1.run(Transport.java:197)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.rmi.transport.Transport.serviceCall(Transport.java:196)
    at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:568)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:826)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.lambda$run$241(TCPTransport.java:683)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:682)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
    at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(StreamRemoteCall.java:276)
    at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:253)
    at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:379)
    at sun.rmi.registry.RegistryImpl_Stub.lookup(Unknown Source)
    at client.Client.main(Client.java:12)

来自服务器的错误：

Sep 07, 2016 9:47:04 AM sun.rmi.server.UnicastServerRef logCall
FINER: RMI TCP Connection(1)-127.0.0.1: [127.0.0.1: sun.rmi.registry.RegistryImpl[0:0:0, 0]: void rebind(java.lang.String, java.rmi.Remote)]
Sep 07, 2016 9:47:04 AM sun.rmi.server.UnicastServerRef logCall
FINER: RMI TCP Connection(2)-127.0.0.1: [127.0.0.1: sun.rmi.transport.DGCImpl[0:0:0, 2]: java.rmi.dgc.Lease dirty(java.rmi.server.ObjID[], long, java.rmi.dgc.Lease)]
Sep 07, 2016 9:47:05 AM sun.rmi.server.UnicastServerRef logCall
FINER: RMI TCP Connection(3)-127.0.0.1: [127.0.0.1: sun.rmi.registry.RegistryImpl[0:0:0, 0]: java.rmi.Remote lookup(java.lang.String)]
Sep 07, 2016 9:47:05 AM sun.rmi.server.UnicastServerRef logCallException
FINE: RMI TCP Connection(3)-127.0.0.1: [127.0.0.1] exception:
java.rmi.NotBoundException: rmi://localhost:1099/Server1
    at sun.rmi.registry.RegistryImpl.lookup(RegistryImpl.java:166)
    at sun.rmi.registry.RegistryImpl_Skel.dispatch(Unknown Source)
    at sun.rmi.server.UnicastServerRef.oldDispatch(UnicastServerRef.java:410)
    at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:268)
    at sun.rmi.transport.Transport$1.run(Transport.java:200)
    at sun.rmi.transport.Transport$1.run(Transport.java:197)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.rmi.transport.Transport.serviceCall(Transport.java:196)
    at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:568)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:826)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.lambda$run$241(TCPTransport.java:683)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:682)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)

我在这里做错了什么？

Answer 1

在Client.java中更改

registry.lookup("rmi://127.0.0.1:1099/Server1")

至

registry.lookup("Server1");

Answer 2

由于使用Registry而不是Naming进行查找，因此应该省略查找字符串的URL部分，就像绑定时所做的那样。您应该只查找Server1，就像在绑定时所做的那样。