Java - 等待流完成写入？

Question

我有一个在 java 中运行的“服务器”，我通过字节数组将文件发送到一个“客户端”（android 系统）。该功能工作正常，但我注意到当我尝试发送更大的文件（1MB +）时，它在关闭之前没有成功写入所有字节（例如：尝试发送 5mb，它只发送了 902 个字节）。有没有办法让代码在关闭流之前等待流完成写入？下面是代码和堆栈跟踪。本质上，发送消息方法在附加和发送文件时调用（在处理 GUI 的类中）。在这种情况下，我并没有尝试从客户端接收数据，只是向客户端发送数据。

编辑：我知道我现在只将字节数组设置为 1MB。我有它 5MB，它仍然只写

EDIT2：我在客户端发布了一些处理接收数据的代码。

public void sendMessage(File file) {
    if(mOut != null) {
        try {
            FileInputStream inStream = new FileInputStream(file);               
            byte[] message = new byte[1024 * 1024];
            inStream.read(message);
            mOut.write(message, 0, message.length);
            mOut.flush();
            inStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        } 
    }
}

public void run() { 
    super.run();
    running = true;
    try {
        System.out.println("S: Connecting...");
        ServerSocket serverSocket = new ServerSocket(SERVERPORT);
        Socket client = serverSocket.accept();
        linked = true;
        System.out.println("S: Receiving...");

        try {
            mOut =client.getOutputStream();
            InputStream in = client.getInputStream();
            while(running) {
                byte[] message = new byte[1024 * 1024];
                 in.read(message);
                if(message != null && messageListener != null) {
                    messageListener.messageReceived(message);
                }
            }
        } catch (Exception ex) {
            System.out.println("S:Error");
            ex.printStackTrace();
        } finally {
            client.close();
            System.out.println("S:Done");
        }
    } catch (Exception ex) {
        System.out.println("S: Error");
        ex.printStackTrace();
    }

}
---------------------------------------------------------------------------
java.net.SocketException: Connection reset by peer: socket write error
at java.net.SocketOutputStream.socketWrite0(Native Method)
at java.net.SocketOutputStream.socketWrite(Unknown Source)
at java.net.SocketOutputStream.write(Unknown Source)
at Server.sendMessage(Server.java:34)
at ServerBoard$2.actionPerformed(ServerBoard.java:57)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$000(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
java.net.SocketException: Connection reset
at java.net.SocketInputStream.read(Unknown Source)
at java.net.SocketInputStream.read(Unknown Source)
at java.net.SocketInputStream.read(Unknown Source)
at Server.run(Server.java:58)

这是客户端的代码sn-p。

    public void run() {
    mRun = true;
    serverMessage = new byte[1024 * 1024];
    try {
        InetAddress serverAddr = InetAddress.getByName(SERVERIP);
        Log.e("TCP Client", "C:Connecting...");
        Socket socket = new Socket(serverAddr, SERVERPORT);
        try {
            in = socket.getInputStream();
            while(mRun) {
                 in.read(serverMessage);
                if(serverMessage != null && mMessageListener != null) {
                    mMessageListener.messageReceived(new String(serverMessage));
            }
                serverMessage = null;
            }

            Log.e("RESPONSE FROM SERVER","S:Received Message: '" + serverMessage + "'");

        } catch(Exception ex) {
            Log.e("TCP","S: Error", ex);
        } finally {
            socket.close();
        }
    } catch(Exception ex) {
        Log.e("TCP","C: Error", ex);
    }
}

Answer 1

一、read的JavaDoc：

从输入流中读取一些字节并将它们存储到 缓冲区数组 b.实际读取的字节数返回为 一个整数。此方法阻塞，直到输入数据可用，结束 检测到文件，或者抛出异常。

由于源是一个套接字，它可能返回比预期更少的字节，即使缓冲区大小为 1 MByte，返回 902 KBytes 也是可以的。您必须循环直到流结束。

以下方法读取所有字节，而不是调用侦听器：

byte[] message = new byte[0]; 
byte[] buffer  = new byte[4096];
int    len;
while(( len = is.read( buffer )) > -1 ) {
   byte[] tmp = new byte[message.length+len];
   System.arraycopy( message, 0, tmp, 0, message.length );
   System.arraycopy( buffer , 0, tmp, message.length, len );
   message = tmp;
}
messageListener.messageReceived( message );

如您所见，会发生很多重新分配：您必须重新设计协议以首先发送文件的大小，然后分配一次接收缓冲区。

Answer 2

您在完成读取之前将读取缓冲区设置为空：

 in = socket.getInputStream();
 while(mRun) {
     in.read(serverMessage);
     if(serverMessage != null && mMessageListener != null) {
         mMessageListener.messageReceived(new String(serverMessage));
     }
     serverMessage = null;
}

这将导致 NullPointerException 并且您的代码将关闭套接字。

Answer 3

设置socket.setSendBufferSize(1024)（用于发送）还确保在接收时读取1024字节块。