java - RMI 远程异常。 RMI 不工作

Question

当我尝试运行我的 RMI 示例时出现远程异常。我不明白为什么。我在不对程序本身或 JVM 进行任何参数的情况下运行该程序。

请帮助我摆脱异常。

非常感谢

这是我得到的异常:

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

这些是我的类(class):

客户端类:

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();
    }
    }
}

远程接口(interface):

package hello;

import java.rmi.Remote;
import java.rmi.RemoteException;

public interface Hello extends Remote {
    String sayHello() throws RemoteException;
}

最后是服务器:

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();
    }
    }
}

Answer 1

注册表或客户端或两者都找不到异常中指定的类。有几种可能的解决方案:

1. 在执行注册表和客户端时将该类包含在类路径中。以及它依赖的所有类，递归直到关闭。

2. 使用 LocateRegistry.createRegistry() 从服务器 JVM 内部启动注册表，它解决了类路径问题，并仅在客户端的类路径中提供必要的类。

3. 使用代码库功能确保所有系统组件都可以访问所需的服务器端类。