ObjectInputStream(socket.getInputStream());不工作

Posted 2023-02-25

【中文标题】ObjectInputStream(socket.getInputStream());不工作

【英文标题】：ObjectInputStream(socket.getInputStream()); does not work

【发布时间】：2012-01-12 17:16:32

【问题描述】：

我正在编写一个与服务器通信的类，但是当它尝试在输入流的帮助下构造 ObjectInputStream 时，程序会冻结。没有异常，程序仍在运行，但挂在尝试构造 ObjectInputstream 的行中。

这是我的问题所在方法的代码：

@Override
public void connect(String ip, int port) throws UnknownHostException, IOException 
    Socket socket = new Socket(ip, port);
    out = new ObjectOutputStream(socket.getOutputStream());
    InputStream is = socket.getInputStream();
    in = new ObjectInputStream(is);

这是整个班级的代码：

package Client;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;


public class MessageStreamerImpl implements MessageStreamer 
    ObjectOutputStream out;
    ObjectInputStream in;

    public MessageStreamerImpl(String ip, int port) throws UnknownHostException, IOException
        connect(ip, port);
    

    public MessageStreamerImpl()
    

    @Override
    public void send(Object message) throws IOException 
        if(out == null) throw new IOException();
        out.writeObject(message);
        out.flush();
    

    @Override
    public Object receive() throws IOException
        try 
            return in.readObject();
         catch (ClassNotFoundException e) 
            throw new IOException();
        
    

    @Override
    public void connect(String ip, int port) throws UnknownHostException, IOException 
        Socket socket = new Socket(ip, port);
        out = new ObjectOutputStream(socket.getOutputStream());
        InputStream is = socket.getInputStream();
        in = new ObjectInputStream(is);
    

在查看 Google 时，我发现了这个：http://www.coderanch.com/t/232944/threads/java/Socket-getInputStream-block。但是我仍然不知道如何解决这个问题，因为我的 ObjectOutputStream 构造函数在 ObjectInputStream 之前。

这是我的服务器代码，也许会有所帮助；）

package Server;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketException;
import java.util.ArrayList;

public class Server 
    ArrayList<Socket> clients = new ArrayList<Socket>();

    public Server(int port)
        try 
            ServerSocket mySocket = new ServerSocket(port);
            waitForClients(mySocket);
         catch (IOException e) 
            System.out.println("Unable to start.");
            e.printStackTrace();
        
    

    private void waitForClients(ServerSocket mySocket) 
        while(true)
            try 
                System.out.println("Ready to receive");
                Socket client = mySocket.accept();
                clients.add(client);
                System.out.println(client.getInetAddress().getHostAddress()+" connected to the Server");
                Thread t = new Thread(new ClientHandler(client));
                t.start();
             catch (IOException e) 
                // TODO Auto-generated catch block
                e.printStackTrace();
            
        
    

    public void shareToAll(Object objectToSchare)
        for(Socket client:clients)
            ObjectOutputStream oos;
            try 
                oos = new ObjectOutputStream(client.getOutputStream());
                oos.writeObject(objectToSchare);
                oos.close();
             catch (IOException e) 
                // TODO Auto-generated catch block
                e.printStackTrace();
            
        
    

    private class ClientHandler implements Runnable
        Socket clientSocket;

        public ClientHandler(Socket clientSocket)
            this.clientSocket = clientSocket;
        
        @Override
        public void run() 
            try 
                ObjectInputStream ois = new ObjectInputStream(clientSocket.getInputStream());
                while(true)
                    try 
                        ois.readObject();

                     catch (ClassNotFoundException | IOException e) 
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    
                
            catch(SocketException e)
                System.out.println(clientSocket.getInetAddress().getHostAddress()+" disconnected from the Server");
                clients.remove(clientSocket);
            catch (IOException e) 
                // TODO Auto-generated catch block
                e.printStackTrace();
            
        
    

感谢您的帮助，我找到了问题所在。它在服务器类中，必须如下所示：

package Server;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketException;
import java.util.ArrayList;

public class Server 
    ArrayList<ObjectOutputStream> clientstreams = new ArrayList<ObjectOutputStream>();

    public Server(int port)
        try 
            ServerSocket mySocket = new ServerSocket(port);
            waitForClients(mySocket);
         catch (IOException e) 
            System.out.println("Unable to start.");
            e.printStackTrace();
        
    

    private void waitForClients(ServerSocket mySocket) 
        while(true)
            try 
                System.out.println("Ready to receive");
                Socket client = mySocket.accept();
                clientstreams.add(new ObjectOutputStream(client.getOutputStream()));
                System.out.println(client.getInetAddress().getHostAddress()+" connected to the Server");
                Thread t = new Thread(new ClientHandler(client));
                t.start();
             catch (IOException e) 
                // TODO Auto-generated catch block
                e.printStackTrace();
            
        
    

    public void shareToAll(Object objectToSchare)
        for(ObjectOutputStream stream:clientstreams)
            try 
                stream.writeObject(objectToSchare);
                stream.flush();
             catch (IOException e) 
                // TODO Auto-generated catch block
                e.printStackTrace();
            
        
    

    private class ClientHandler implements Runnable
        Socket clientSocket;

        public ClientHandler(Socket clientSocket)
            this.clientSocket = clientSocket;
        
        @Override
        public void run() 
            try 
                ObjectInputStream ois = new ObjectInputStream(clientSocket.getInputStream());
                while(true)
                    try 
                        ois.readObject();

                     catch (ClassNotFoundException | IOException e) 
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    
                
            catch(SocketException e)
                System.out.println(clientSocket.getInetAddress().getHostAddress()+" disconnected from the Server");
                clientstreams.remove(clientSocket);
            catch (IOException e) 
                // TODO Auto-generated catch block
                e.printStackTrace();
            
        
       

您在方法 waitForClients() 中看到的变化最多，但我也改变了 ArrayList 和 shareToAll 方法的概念。

【参考方案1】：

ObjectInputStream 构造函数从给定的 InputStream 中读取数据。为了使其工作，您必须在构造后立即刷新 ObjectOutputStream（以写入初始标头），然后再尝试打开 ObjectInputStream。此外，如果您想在每个连接中发送多个对象，则必须打开一次 ObjectOutputStream 并在套接字的整个生命周期内使用它（例如，您的 shareToAll 方法）。

【讨论】：

不知道你是不是也这样，但是我找到了原因。错误出现在方法 waitForClients() 的服务器类中，我必须在 Socket client = mySocket.accept(); 之后生成一个输出流与 client.getOutputstream();.否则客户端被阻塞等待OutputStream（他的InputStream）。谢谢

我编辑了这个问题，因为我还不能回答我自己的问题。

您仍然不应该每次都重新定义输入和输出流。它们应该在 ClientHandler 类中是全局的。

他们是。或者他们几乎是......但我现在只建造一次。输出流现在在我的 Arraylist 中表示，输入流在我的 ClientHandler 中的 while 循环之前被定义一次；）