创建简单的RMI应用程序时出现“ClassCastException:$ Proxy0无法转换”错误

时间:2012-03-08 15:34:49

标签: java rmi

我正在创建我的第一个非常简单的RMI客户端 - 服务器应用程序。

以下是代码:

接口“ICommunication”

package itu.exercies.RMI.server;

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

public interface ICommunication extends Remote  
{
    public String doCommunicate(String name) throws RemoteException; 

}

接口实现“CommunicationImpl”:

package itu.exercies.RMI.server;

import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;

public class CommunicationImpl extends UnicastRemoteObject implements ICommunication {

    /**
     * 
     */
    private static final long serialVersionUID = 1L;

    public CommunicationImpl() throws RemoteException {
        super();

    }

    @Override
    public String doCommunicate(String name) throws RemoteException {

        return "Hello this is server , whats up " +name+ " ?!\n";
    }

}

这是我的服务器“CommunicationServer”的主要类:

package itu.exercies.RMI.server;

import java.net.MalformedURLException;
import java.rmi.Naming;
import java.rmi.RemoteException;


public class CommunicationServer {
    /**
     * @param args
     * @throws RemoteException 
     * @throws MalformedURLException 
     */
    public static void main(String[] args) throws RemoteException, MalformedURLException {
        CommunicationImpl imp = new CommunicationImpl();
        Naming.rebind("CommunicationImpl", imp);
        System.out.println("Server started...");
        System.out.println("Object successfully registered. It is bound to the name 'CommunicationImpl'.");

    }

}

这是我的客户“CommunicationClient”:

package itu.exercies.RMI.client;

import java.net.MalformedURLException;
import java.rmi.Naming;
import java.rmi.NotBoundException;
import java.rmi.RemoteException;

import itu.exercies.RMI.server.CommunicationImpl;

public class CommunicationClient {
    public static void main(String[] args) throws MalformedURLException, RemoteException, NotBoundException {

        String url = new String("rmi://localhost/CommunicationImpl");
        CommunicationImpl comm = (CommunicationImpl)Naming.lookup(url);
        String reply = comm.doCommunicate("Wiktor");
        System.out.println(reply);


    }

}

现在,当我尝试运行它时:

  1. 使用终端
  2. 导航到项目的bin目录
  3. 我从那里开始rmiregistry
  4. 我从新的终端窗口运行我的CommunicationServer(并打印出消息,因此它似乎正常工作)
  5. 我打开第三个终端窗口,当我尝试运行我的CommunicationClient时,它会抛出异常。
  6.   

    java itu.exercies.RMI.client.CommunicationClientException in thread“main”java.lang.ClassCastException:$ Proxy0无法强制转换为itu.exercies.RMI.server.CommunicationImpl       at itu.exercies.RMI.client.CommunicationClient.main(CommunicationClient.java:14)

    到目前为止,我试图通过使用rmic创建一个'CommunicationImpl'对象的存根来修复它,但是现在而不是'$ Proxy0',错误引用'CommunicationImpl_Stub':

      

    线程“main”中的异常java.lang.ClassCastException:itu.exercies.RMI.server.CommunicationImpl_Stub无法强制转换为itu.exercies.RMI.server.CommunicationImpl       at itu.exercies.RMI.client.CommunicationClient.main(CommunicationClient.java:14)

    此时我不知道是在寻找错误。有人可以给我任何建议吗?

1 个答案:

答案 0 :(得分:23)

替换

CommunicationImpl comm = (CommunicationImpl) Naming.lookup(url);

ICommunication comm = (ICommunication) Naming.lookup(url);

CommunicationImplICommunication的服务器实现。客户既不知道也不关心实现,只关心接口。