Java 一个绑定的RMI名称可由多个客户端使用？

我试图在一台（96 Ram）机器上运行3台RMI服务器。来自三个不同机器的客户端正在调用，但对于三个客户端，我给出了三个不同的端口号，并且所有三个客户端的绑定对象名称也不同

---

对于前2个客户机，我得到了输出，对于第1个客户机，我没有得到任何输出。只有“空指针异常”我在客户端得到。在服务器端，我在所有3台服务器上都给出了-Xms250m到-xmx20g。在客户机上，我提供的所有8 GB ram都是-Xmx6g。

您需要使用自定义的RMIRegistry端口，以便在同一台机器上运行两个或多个注册表实例。请参阅此完全工作的RMI服务器和客户端示例，您可以运行多个连接到同一远程对象实例的客户端。记住同步服务实现的内部行为

import java.util.*;
import java.rmi.*;
import java.rmi.registry.Registry;
import java.rmi.registry.LocateRegistry;
import java.rmi.server.UnicastRemoteObject;
import java.rmi.server.ExportException;

public class RMITest1Client {

    private static Random randomInt = new Random();
    public static int getRandomInt(int min, int max) {
        int range = (max - min) + 1;
        return randomInt.nextInt(range) + min;
    }

    public static void main(String[] args) throws Exception {
        String rmiEndPoint = args[0];
        String serviceName = args[1];
        CounterService counter = (CounterService)Naming.lookup(rmiEndPoint+"/"+serviceName);
        System.out.println("Connected to " + rmiEndPoint+"/"+serviceName);

        for(int idx=0; idx<10; idx++) {
            System.out.println("getValue="+counter.getValue());
            Thread.sleep(getRandomInt(1, 5)*1000);
            counter.setValue( "val"+getRandomInt(100, 999) );
            Thread.sleep(getRandomInt(1, 5)*1000);
        }
    }

}

- - - - - -

import java.rmi.*;
import java.rmi.registry.Registry;
import java.rmi.registry.LocateRegistry;
import java.rmi.server.UnicastRemoteObject;
import java.rmi.server.ExportException;

public class RMITest1Server {

    public static void main(String[] args) throws Exception {
        // create the RMIregistry service
        int port = Integer.parseInt(args[0]);
        Registry registry;
        try {
            System.out.println("RMIRegistry on port " + port);
            registry = LocateRegistry.createRegistry(port);
        } catch (ExportException ex) {
            // registry may already be created by another process,
            // get reference to an existing registry instance.
            System.out.println("Creating registry failed, try to connect an existing registry, ex="+ex.getMessage());
            registry = LocateRegistry.getRegistry(port);
        }

        CounterService counter = new CounterServiceImpl("counter1");
        UnicastRemoteObject.exportObject(counter, port);
        registry.rebind("counter1", counter);

        counter = new CounterServiceImpl("counter2");
        UnicastRemoteObject.exportObject(counter, port);
        registry.rebind("counter2", counter);

        System.out.println("Running...");
        Thread.sleep(30000);

        // close registry objects
        for(String serviceName : registry.list()) {
            try {
                System.out.println("RMIRegistry unbind " + serviceName);
                Remote obj = (Remote)registry.lookup(serviceName);
                UnicastRemoteObject.unexportObject(obj, true); 
            } catch (Exception ex) { } 
            try { registry.unbind(serviceName); } catch (Exception ex) { }
        }
        System.out.println("RMIRegistry closed");
        System.exit(0); // mandatory if RMIRegistry was started in this JVM instance
    }

}

这是一个在服务器机器上运行的远程服务接口和实现

import java.rmi.*;
public interface CounterService extends Remote {
    public void setValue(String value) throws RemoteException;
    public String getValue() throws RemoteException;
}

- - - - - -

import java.rmi.*;
public class CounterServiceImpl implements CounterService {
    private int callCount=0;
    private String name;
    private String value;

    public CounterServiceImpl(String name) {
        this.name=name;
        this.value="";
    }

    public synchronized void setValue(String value) throws RemoteException {
        callCount++;
        this.value=value;
    }

    public synchronized String getValue() throws RemoteException {
        callCount++;
        return String.format("%s (name=%s, callcount=%d)", value, name, callCount);
    }   
}

下面是一个RMI客户机和服务器实现

import java.util.*;
import java.rmi.*;
import java.rmi.registry.Registry;
import java.rmi.registry.LocateRegistry;
import java.rmi.server.UnicastRemoteObject;
import java.rmi.server.ExportException;

public class RMITest1Client {

    private static Random randomInt = new Random();
    public static int getRandomInt(int min, int max) {
        int range = (max - min) + 1;
        return randomInt.nextInt(range) + min;
    }

    public static void main(String[] args) throws Exception {
        String rmiEndPoint = args[0];
        String serviceName = args[1];
        CounterService counter = (CounterService)Naming.lookup(rmiEndPoint+"/"+serviceName);
        System.out.println("Connected to " + rmiEndPoint+"/"+serviceName);

        for(int idx=0; idx<10; idx++) {
            System.out.println("getValue="+counter.getValue());
            Thread.sleep(getRandomInt(1, 5)*1000);
            counter.setValue( "val"+getRandomInt(100, 999) );
            Thread.sleep(getRandomInt(1, 5)*1000);
        }
    }

}

- - - - - -

import java.rmi.*;
import java.rmi.registry.Registry;
import java.rmi.registry.LocateRegistry;
import java.rmi.server.UnicastRemoteObject;
import java.rmi.server.ExportException;

public class RMITest1Server {

    public static void main(String[] args) throws Exception {
        // create the RMIregistry service
        int port = Integer.parseInt(args[0]);
        Registry registry;
        try {
            System.out.println("RMIRegistry on port " + port);
            registry = LocateRegistry.createRegistry(port);
        } catch (ExportException ex) {
            // registry may already be created by another process,
            // get reference to an existing registry instance.
            System.out.println("Creating registry failed, try to connect an existing registry, ex="+ex.getMessage());
            registry = LocateRegistry.getRegistry(port);
        }

        CounterService counter = new CounterServiceImpl("counter1");
        UnicastRemoteObject.exportObject(counter, port);
        registry.rebind("counter1", counter);

        counter = new CounterServiceImpl("counter2");
        UnicastRemoteObject.exportObject(counter, port);
        registry.rebind("counter2", counter);

        System.out.println("Running...");
        Thread.sleep(30000);

        // close registry objects
        for(String serviceName : registry.list()) {
            try {
                System.out.println("RMIRegistry unbind " + serviceName);
                Remote obj = (Remote)registry.lookup(serviceName);
                UnicastRemoteObject.unexportObject(obj, true); 
            } catch (Exception ex) { } 
            try { registry.unbind(serviceName); } catch (Exception ex) { }
        }
        System.out.println("RMIRegistry closed");
        System.exit(0); // mandatory if RMIRegistry was started in this JVM instance
    }

}

---

您的问题是什么？因为两个以上的客户端无法同时访问RMI服务器，直到没有问题为止。@AshutoshKumar“两个以上的客户端无法同时访问RMI服务器”为false。你不需要这些。只需使用一个端口和一个远程对象。安全策略文件在客户端和服务器端是必需的吗？@AshutoshKumar No。