Java - 通过 ObjectOutputStream read/writeObject() 从服务器向客户端发送 ImageIcons 时出错

Question

背景很少，目前正在尝试完成我的学位作业，尝试实现一个“拍卖行”本地主机服务器客户端程序，其中客户端可以对服务器上保存的元素进行竞价。当新客户端连接到服务器时，用户必须注册他/她的名字，然后服务器将向客户端发送所有项目信息。

目前，所有其他信息都正确发送，但是当我尝试通过 ObjectOutputStream 将项目的图像发送到客户端时，服务器总是无法发送 ImageIcons，当我断开客户端连接时，我遇到了以下错误消息:

    Exception in thread "main" java.io.StreamCorruptedException: invalid type code: 53 at java.io.ObjectInputStream.readObject0(Unknown Source)
   at java.io.ObjectInputStream.readObject(Unknown Source)
   at AuctionClient.retrieveItemInformation(AuctionClient.java:365)
   at AuctionClient.main(AuctionClient.java:341)

我认为这可能与我尝试直接通过输出流发送 ImageIcons 而不使用可序列化有关，但我们的 java 讲师告诉我们 ImageIcon 不需要它才能正常运行，所以我不确定，有什么建议吗会很好!我将把服务器/客户端的代码放在下面!

服务器线程代码:

public ClientHandler(Socket socket, BiddingItem item1, BiddingItem item2, int number) throws IOException
{
    client = socket;
    outputImage = new ObjectOutputStream(client.getOutputStream());
    input = new Scanner(client.getInputStream());
    output = new PrintWriter(client.getOutputStream(), true);
    startedItem1 = item1;
    startedItem2 = item2;
    clientNumber = number;
    images = new ImageIcon[2];
    images[0] = startedItem1.getImage();
    images[1] = startedItem2.getImage();
}

尝试向客户端发送信息:

public void run()
{
    //previous code...
    for (int i=0; i<images.length;++i)
    {
        try 
        {
            outputImage.writeObject(images[i]);
        }
        catch (IOException ioEx)
        {
            System.out.println("\n**ERROR: Unable to send Item " + i + " image to client!**");
        }
        try 
        {
            outputImage.flush();
        } 
        catch (IOException e1) 
        {
            System.out.println("\n**ERROR: Unable to flush OutputObjectStream!**");
        }
    }

客户端创建输入流:

public static void main(String[] args) throws IOException, InterruptedException, ClassNotFoundException 
{
    //previous code
    try
    {
        txtBoxServerMessage.setText("CLIENT: Attempting to connect to server...");
        Thread.sleep(2000);
        socket = new Socket(host, PORT);
        inputFromServer = new Scanner(socket.getInputStream());
        inputImageFromServer = new ObjectInputStream(socket.getInputStream());
        outputToServer = new PrintWriter(socket.getOutputStream(), true);
    }
    catch(IOException ioEx)
    {
        txtBoxServerMessage.setText("CLIENT-ERROR: Unable to connect to server! Exiting...");
        Thread.sleep(2000);
        System.exit(1);
    }
}

客户端用来接受信息的函数:

private static void retrieveItemInformation() throws InterruptedException, ClassNotFoundException, IOException
{
    txtBoxServerMessage.setText("CLIENT: Waiting for Item Information...");
    Thread.sleep(3000);

    clientNumber = Integer.parseInt(inputFromServer.nextLine());

    item1Code = inputFromServer.nextLine();
    item1Desc = inputFromServer.nextLine();
    item1Deadline = inputFromServer.nextLine();
    item1AuctionValue = Double.parseDouble(inputFromServer.nextLine());

    item2Code = inputFromServer.nextLine();
    item2Desc = inputFromServer.nextLine();
    item2Deadline = inputFromServer.nextLine();
    item2AuctionValue = Double.parseDouble(inputFromServer.nextLine());

    item1Image = (ImageIcon)inputImageFromServer.readObject(); // READING IMAGE 1
    item2Image = (ImageIcon)inputImageFromServer.readObject(); // READING IMAGE 2

    txtBoxServerMessage.setText("DEBUG: FINISHED IMAGE");
    txtBoxServerMessage.setText("CLIENT: Information Recieved! Displaying...");
    Thread.sleep(1000);
    comboItemSelect.addItem(item1Code);
    comboItemSelect.addItem(item2Code);
    txtBoxClientNumber.setText(String.valueOf(clientNumber));

    updateDisplay();

}

干杯!

中号

Answer 1

问题是这样的:

outputImage = new ObjectOutputStream(client.getOutputStream());
// ...
output = new PrintWriter(client.getOutputStream(), true);

您不能将单个 OutputStream 包装在两个不同的包装器中。它们各自的状态和缓冲不兼容。

特别是，如果您使用 ObjectOutputStream 以外的任何内容写入哪怕一个字节，对象流就会损坏。

如果要同时发送对象和文本，可以将 String 对象写入 ObjectOutputStream。您也可以直接调用ObjectOutputStream.writeUTF。