仅当由服务器发送到客户端时才能反序列化类，反之亦然

Question

流过去可以工作，但两天前突然停止了，我无法修复它。

客户端创建并成功发送一个 User 对象和一个 Message 对象（由客户端序列化并由服务器反序列化）。当客户端收到两个类中的任何一个（由服务器序列化并由客户端反序列化）时，我会遇到异常，主要是：

java.io.UTFDataFormatException
    at java.base/java.io.ObjectInputStream$BlockDataInputStream.readUTFSpan(ObjectInputStream.java:3704)
    at java.base/java.io.ObjectInputStream$BlockDataInputStream.readUTFBody(ObjectInputStream.java:3658)
    at java.base/java.io.ObjectInputStream$BlockDataInputStream.readUTF(ObjectInputStream.java:3458)
    at java.base/java.io.ObjectInputStream.readUTF(ObjectInputStream.java:1239)
    at java.base/java.io.ObjectStreamClass.readNonProxy(ObjectStreamClass.java:804)
    at java.base/java.io.ObjectInputStream.readClassDescriptor(ObjectInputStream.java:988)
    at java.base/java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:2032)
    at java.base/java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1907)
    at java.base/java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:2209)
    at java.base/java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1742)
    at java.base/java.io.ObjectInputStream.readObject(ObjectInputStream.java:514)
    at java.base/java.io.ObjectInputStream.readObject(ObjectInputStream.java:472)
    at Model.MessageClient$1.run(MessageClient.java:69)
    at java.base/java.lang.Thread.run(Thread.java:833)

每隔一段时间，我会得到：

java.io.InvalidClassException: Model.Message; class invalid for deserialization
    at java.base/java.io.ObjectStreamClass$ExceptionInfo.newInvalidClassException(ObjectStreamClass.java:174)
    at java.base/java.io.ObjectStreamClass.checkDeserialize(ObjectStreamClass.java:921)
    at java.base/java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:2210)
    at java.base/java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1742)
    at java.base/java.io.ObjectInputStream.readObject(ObjectInputStream.java:514)
    at java.base/java.io.ObjectInputStream.readObject(ObjectInputStream.java:472)

客户端 - 流

public MessageClient(String ip, int port, String usernameStr, ImageIcon icon, Controller controller) {
    this.user = new User(usernameStr, icon);
    this.controller = controller;
    this.port = port;
    this.ip = ip;
    this.messageBuffer = new Buffer<>();
    this.contacts = new ArrayList<>(); //(ArrayList<Model.User>) readObjectFromFile("files/contacts");
    setUpStreams();
    setUpThreads();
}

public void setUpStreams(){
    try {
        s = new Socket(ip, port);
        try {
            ois = new ObjectInputStream(s.getInputStream());
            oos = new ObjectOutputStream(s.getOutputStream());
            oos.writeObject(user);
            oos.flush();
            users = new ArrayList<>();
            setUpThreads();
        } catch (IOException e) {
            e.printStackTrace();
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}

public void setUpThreads(){
    t1 = new Thread(new Runnable() {
        @Override
        public void run() {
            while (!Thread.interrupted()) {
                try {
                    Object o = ois.readObject();
                    if (o.getClass().isAssignableFrom(Message.class)) {
                        receiveMessage((Message) o);
                    }
                    if (o.getClass().isAssignableFrom(ArrayList.class)) {
                        updateUsers((ArrayList<Model.User>) o);
                    }
                } catch(EOFException e){
                    System.out.println("stopped");
                    t2.stop();
                    t1.stop();
                } catch(IOException | ClassNotFoundException e){
                    try {
                        Thread.sleep(2000);
                    } catch (InterruptedException ex) {
                        ex.printStackTrace();
                    }
                    e.printStackTrace();
                }
            }
        }
    });
    t2 = new Thread(new Runnable() {
        @Override
        public void run() {
            while (!Thread.interrupted()) {
                try {
                    Message currMessage = messageBuffer.get();
                    oos.writeObject(currMessage);
                    oos.flush();
                } catch(IOException | InterruptedException e){
                    e.printStackTrace();
                }

            }
        }
    });
    t1.start();
    t2.start();
}

服务器端流

@Override
public synchronized void run() {

    while (socket.isConnected() && !socket.isClosed()) {
            try {
                Object o = ois.readObject();
                ih.addToBuffer((Model.Message) o);
            } catch (EOFException e) {
                try {
                    socket.close();
                    t2.stop();
                    t1.stop();
                } catch (IOException ex) {
                    ex.printStackTrace();
                }
            } catch (IOException | ClassNotFoundException e) {
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException ex) {
                    ex.printStackTrace();
                }
            }

    }
    chm.put(user, null);
    clients.remove(this);
    sendAll(new Message(user.getUsername() + " has disconnected", null));

}

private class InputHandler implements Runnable{
    private Buffer<Model.Message> inputBuffer;

    public InputHandler(){
        inputBuffer = new Buffer<>();
    }

    public void addToBuffer(Message msg){
        inputBuffer.put(msg);
    }

    @Override
    public synchronized void run() {
        Object o = null;
        while (!Thread.interrupted()) {
            Message temp = null;
            Message sendable = null;
            try {
                temp = inputBuffer.get();
                sendable = new Message(temp.getText(), temp.getIcon(), temp.getRecipients(), temp.getSender());
                sendable.setCurrID();
                sendable.setUploaded(new Timestamp(System.currentTimeMillis()));
                sendSelect(sendable ,sendable.getSender());
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

        }
    }
}
public void sendSelect(Message msg, User selectedUser){
        Client currClient;
        if(!chm.containsKey(selectedUser)) {
            try {
                oos.writeObject(new Message(selectedUser.getUsername() + "not found", null));
                oos.flush();
            } catch (IOException e) {
                e.printStackTrace();
            }
        } else if ((currClient = chm.get(selectedUser)) != null) {
            try {
                currClient.oos.writeObject((Model.Message) msg);
                currClient.oos.flush();
                msg.setDownloaded(new Timestamp(System.currentTimeMillis()));
                callback.downloadTimestamp(msg);
            } catch (IOException e) {
                e.printStackTrace();
            }

        } else {
            addUnsent(selectedUser, msg);
        }
}

我序列化的类复制并粘贴。

类路径是相同的，所有字段都是可序列化的并且具有无参数构造函数。我还确保两个编码都设置为 UTF-8

Message

package Model;

import javax.swing.*;
import java.io.*;
import java.sql.Timestamp;
import java.util.LinkedList;

public class Message implements Serializable{
    @Serial
    private static final long serialVersionUID = -3930131856060689940L;

    private static int nextID = 0;
    private int currID;

    private final String text;
    private final ImageIcon icon;

    private Timestamp uploaded;
    private Timestamp downloaded;

    private final User sender;
    private final LinkedList<User> recipients;

    public Message(){
        currID = nextID;
        nextID++;
        this.text = null;
        this.icon = null;
        sender = null;
        recipients = null;
    }
    public Message(String text, User sender){
        currID = nextID;
        nextID++;
        this.text = text;
        this.icon = null;
        this.sender = sender;
        this.recipients = null;

    }
    public Message(String text, ImageIcon icon, User sender) {
        currID = nextID;
        nextID++;
        this.text = text;
        this.icon = icon;
        this.sender = sender;
        this.recipients = null;

    }
    public Message(String text, ImageIcon icon, LinkedList<User> recipients, User sender) {
        currID = nextID;
        nextID++;
        this.text = text;
        this.icon = icon;
        this.sender = sender;
        this.recipients = recipients;

    }

    @Override
    public boolean equals(Object obj) {
        if(obj instanceof Message){
            if( ((Message) obj).getCurrID() == this.currID ){
                return true;
            }
        }
        return false;
    }
    public String getText() {
        return text;
    }
    public ImageIcon getIcon() {
        return icon;
    }
    public Timestamp getUploaded() {
        return uploaded;
    }
    public Timestamp getDownloaded() {
        return downloaded;
    }
    public Model.User getSender(){return sender;}
    public int getCurrID(){return currID;}
    public void setCurrID(){currID = nextID; nextID++;}
    public LinkedList<User> getRecipients(){
        return recipients;
    }
    public void setUploaded(Timestamp uploaded) {
        this.uploaded = uploaded;
    }
    public void setDownloaded(Timestamp downloaded) {
        this.downloaded = downloaded;
    }
}

User

package Model;

import javax.swing.*;
import java.io.Serial;
import java.io.Serializable;

public class User implements Serializable{
    @Serial
    private static final long serialVersionUID = -5886308724572898536L;

    private String username;
    private ImageIcon image;

    public User(String username, ImageIcon image){
        this.username = username;
        this.image = image;
    }

    public int hashCode() {
        return username.hashCode();
    }

    public boolean equals(Object obj) {
        if(obj!=null && obj instanceof User)
            return username.equals(((User)obj).getUsername());
        return false;
    }

    public String getUsername() {
        return username;
    }

    @Override
    public String toString(){
        return username;
    }
}

Answer 1

问题是我调用了 setUpThread() 两次，弄乱了输入流。因此，如果遇到此类问题，请确保不要多次初始化线程（从套接字读取输入流）。