ServerSocket 接受方法 - 如何向下转换为子类类型？

发布于 2024-10-21 00:03:11 字数 781 浏览 4 评论 0原文

我有一个扩展 Socket 类的 ClientSocket 类。我扩展 Socket 类的原因是我想包含一个 String clientId 来唯一标识套接字另一端的客户端。我还有一个名为“getClientId”的方法，它返回 clientId。

我的服务器上运行着一个 ServerSocket 实例，它接受套接字连接，如下所示：

public Socket acceptNextConnection() throws IOException {
    Socket socket = serverSocket.accept();

    // put the client socket into the map
    ClientSocket clientSocket = (ClientSocket) socket;
    clientConnections.put(clientSocket.getClientId(), clientSocket);

    return clientSocket;
}

如您所见，我的转换不正确，因为 Socket 实例不是 ClientSocket 实例，因此我得到了类转换异常，正如我所期望的。从代码中可以明显看出，我想在类 ClientSocket 上调用“getClientId”。但是我不能这样做，因为 serverSocket.accept 方法在运行时返回 Socket 对象，而不是 ClientSocket。我的问题是，有办法解决这个问题吗？如果没有，是否有一种更简洁的方法来做我想要的事情，即能够唯一标识绑定到客户端的套接字？ IP 地址可能会发生变化。

感谢您的帮助。

原文

I have a class ClientSocket that extends class Socket. The reason I extend class Socket, is that I want to include a String clientId that uniquely identifies a client on the other side of the socket. I also have a method called 'getClientId' that returns the clientId.

I have a ServerSocket instance running on my server that accepts socket connections like so:

public Socket acceptNextConnection() throws IOException {
    Socket socket = serverSocket.accept();

    // put the client socket into the map
    ClientSocket clientSocket = (ClientSocket) socket;
    clientConnections.put(clientSocket.getClientId(), clientSocket);

    return clientSocket;
}

As you can see, my cast here is incorrect as a Socket instance IS NOT a ClientSocket instance and so I get a class cast exception, as I expected. As is evident in the code, I want to call 'getClientId' on class ClientSocket. However I can't do this because the serverSocket.accept method returns a Socket object at runtime, not a ClientSocket. My question is, is there a way around this? If not, is there a neater way of doing what I want, which is being able to uniquely identify a socket that is bound to a client? An ip address can be subject to change.

Thanks for the help.

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拥抱我好吗 2024-10-28 00:03:11

您可以拥有一个从接受返回 ClientSocket 的 ServerClientSocket。类似的东西

public class ServerClientSocket extends ServerSocket {
  public ClientSocket accept() throws IOException {
  if (isClosed())
    throw new SocketException("Socket is closed");
  if (!isBound())
    throw new SocketException("Socket is not bound yet");
  ClientSocket s = new ClientSocket((SocketImpl) null);
  implAccept(s);
  return s;
  }
}

You can have a ServerClientSocket which return a ClientSocket from accept. Something like

public class ServerClientSocket extends ServerSocket {
  public ClientSocket accept() throws IOException {
  if (isClosed())
    throw new SocketException("Socket is closed");
  if (!isBound())
    throw new SocketException("Socket is not bound yet");
  ClientSocket s = new ClientSocket((SocketImpl) null);
  implAccept(s);
  return s;
  }
}

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