Java - 等待流完成寫入？

Question

我有一個在 java 中運行的“服務器”，我通過字節數組將文件發送到“客戶端”（android 系統）。 該功能運行良好，但我注意到當我嘗試發送更大的文件 (1MB+) 時，它在關閉之前沒有成功寫入所有字節（例如：嘗試發送 5mb，它只發送了 902 個字節）。 有沒有辦法讓代碼在關閉流之前等待流完成寫入？ 下面是代碼和堆棧跟蹤。 本質上，當附加和發送文件時（在處理 GUI 的類中）調用發送消息方法。 在這種情況下，我沒有嘗試從客戶端接收數據，只是將數據發送到客戶端。

編輯：我知道我現在只將字節數組設置為 1MB。 我有它 5MB，它仍然只寫 <1MB。 即使在 1MB 時，它仍然只寫入 902 個字節。

EDIT2：我在客戶端上發布了一些處理接收數據的代碼。

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)

這是客戶端的代碼片段。

    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

首先， 讀取的JavaDoc：

從輸入流中讀取一定數量的字節並將它們存儲到緩沖區數組 b 中。 實際讀取的字節數作為整數返回。 此方法會阻塞，直到輸入數據可用、檢測到文件結尾或拋出異常。

由於源是一個套接字，它可能返回比預期少的字節，即使緩沖區的大小為 1 MB，返回 902 KB 也可以。 你必須循環直到流結束。

以下方法讀取所有字節，而不是調用偵聽器：

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 );

如您所見，發生了很多重新分配：您必須重新設計協議以首先發送文件的大小並分配一次接收緩沖區。

Answer 2

在完成閱讀之前，您將讀取緩沖區設置為 null：

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

這將導致 NullPointerException 並且您的代碼將關閉套接字。

Answer 3

設置socket.setSendBufferSize(1024) （你用來發送的）也確保在接收時你讀取了1024字節的塊。