Java ObjectInputStream(socket.getInputStream())捕获null对象

Question

我正在制作一对客户端-服务器。我的客户端很好地连接到服务器，它通过套接字创建ObjectInputStream（socket.getInputStream（）），从服务器到客户端，反之亦然。然后，出于某种神秘的原因，我的服务器的ObjectInputStream不知何故捕获了一个空对象。客户端没有通过套接字发送任何东西（我确实在对象发送方法上放置了/../来确保这一点，甚至System.out.print打印了之前发送的所有对象）服务器只捕获了一次神秘对象，之后客户端发送的所有对象都正常工作。。

class ClientThread extends Thread {
        //The socket where to listen/talk
        Socket socket;
        ObjectInputStream sInput;
        ObjectOutputStream sOutput;
        InputStream fInput;
        OutputStream Output;
        //my unique id (easier for deconnection)
        int id;
        //Objects that we will be receiving
        Incomingdata datain;
        //the date we connect
        String date;
        Player player;
        boolean Connected = false;
        //Constructor
        ClientThread(Socket socket){
            id = uniqueId++;
            this.socket = socket;
            try{
                sOutput = new ObjectOutputStream(socket.getOutputStream());
                sInput = new ObjectInputStream(socket.getInputStream());
                Output = socket.getOutputStream();
            } catch (Exception e){
                System.out.println("Couldn't create Input/Output streams");
            }
            date = new Date().toString();
        }
        // what will run forever
        public void run() {
            // to loop until LOGOUT
            Connected = true;
            while(Connected) {
                try {
                    datain = (Incomingdata) sInput.readObject(); //<--- this catches the mystical null! Even if nothing is sent over the socket?
                }
                catch (IOException e) {
                    TextArea.AddLine("Exception reading Streams: " + e);
                    break;              
                }
                catch(ClassNotFoundException e2) {
                    break;
                }

Answer 1

只有发送null，才能接收null。

（人们普遍误解readObject()在流的末尾返回null。事实并非如此。）