java - RMI NotSerializableException 尽管它是一个远程对象

Question

我正在编写一个基于 RMI 的小型聊天应用程序。

思路是:Client在Server上注册自己，Server每次收到一个Client的消息，就把这条消息推送给所有其他Client。

但是我收到了一个 NotSerializableException，尽管我作为方法参数传递的对象实现了 Remote 接口(interface)。

这是一些代码:(有问题的部分是 this.chatServ.registriereClient(this); (ClientChat 实现)中的 this 参数)

(ClientChat)接口(interface):

public interface ChatClient extends Remote
{

}

(ClientChat)实现:

public class ChatClientImpl implements ChatClient
{

    ChatServer chatServ;
    String clientName;

    public ChatClientImpl(String clientName, ChatServer chatServ) {
        this.chatServ = chatServ;
        this.clientName = clientName;
        try {
            this.chatServ.registriereClient(this);
        } catch (RemoteException e) {
            e.printStackTrace();
        }
    }
}

(服务器聊天)接口(interface)

public interface ChatServer extends Remote
{
        void registriereClient(ChatClient client) throws RemoteException;

}

(服务器聊天)实现

public class LobbyChatServerImpl implements ChatServer
{

    ArrayList<ChatClient> clientListe = null;

    @Override
    public void registriereClient(ChatClient client) {
        System.out.println("Client registriert");
        this.clientListe.add(client);
    }
}

客户:

  public static void main(String[] args) {
        ChatServer lobbyChatServer = null;
        try {
            Registry registry = LocateRegistry.getRegistry(Server.RMI_PORT);
            lobbyChatServer = (ChatServer) registry.lookup("LobbyChatServer");

        } catch (RemoteException e) {
            e.printStackTrace();
        } catch (NotBoundException e) {
            e.printStackTrace();
        }

        ChatClient lobbyChat = new ChatClientImpl(name, lobbyChatServer);
  }

服务器:

    public static void main(String[] args) {
        try {
            if (System.getSecurityManager() == null) {
                System.setSecurityManager(new RMISecurityManager());
            }

            Registry registry = LocateRegistry.getRegistry(RMI_PORT);

            ChatServer lobbyChatStub = (ChatServer)UnicastRemoteObject.exportObject(new LobbyChatServerImpl(), 0);
            registry.bind("LobbyChatServer", lobbyChatStub);

        } catch (RemoteException e) {
            e.printStackTrace();
        } catch (AlreadyBoundException e) {
            e.printStackTrace();
        }
    }

异常(exception):

java.rmi.MarshalException: error marshalling arguments; nested exception is: 
    java.io.NotSerializableException: de.XX.Chat.ChatClientImpl
    at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:156)
    at java.rmi.server.RemoteObjectInvocationHandler.invokeRemoteMethod(RemoteObjectInvocationHandler.java:194)
    at java.rmi.server.RemoteObjectInvocationHandler.invoke(RemoteObjectInvocationHandler.java:148)
    at $Proxy0.registriereClient(Unknown Source)
    at de.XX.Chat.ChatClientImpl.<init>(ChatClientImpl.java:19)
    at de.XX.Client.main(Client.java:49)
Caused by: java.io.NotSerializableException: de.XX.Chat.ChatClientImpl
    at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1180)
    at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:346)
    at sun.rmi.server.UnicastRef.marshalValue(UnicastRef.java:292)
    at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:151)
    ... 5 more

如前所述，尽管 ChatClientImpl 已经是 Remote，但我想知道为什么会出现这种异常。

希望你能帮助我:)

Answer 1

作为远程方法的参数或结果传递的对象必须是:

1. 可序列化(或可外部化)，或

2. 导出远程对象。

你的两者都不是。但是，因为它实现了一个 Remote 接口(interface)，这显然是您想要的 (2)。扩展 UnicastRemoteObject 的对象在构造时自动导出。不需要的对象必须通过 UnicastRemoteObject.exportObject() 显式导出。