Java - 等待流完成寫入？

Question

我有一個運行在java中的「服務器」，我通過字節數組發送文件到「客戶端」（android系統）。該功能工作正常，但我注意到當我嘗試發送更大的文件（1MB +）時，在關閉之前它沒有成功寫入所有字節（例如：試圖發送5MB，並且它只發送902字節）。有沒有辦法讓代碼在關閉流之前等待流完成寫入？以下是代碼和堆棧跟蹤。實質上，發送消息方法在附加和發送文件時（在處理GUI的類中）被調用。在這種情況下，我沒有試圖從客戶端接收數據，只是發送數據到客戶端。

編輯：我知道我現在只有字節數組設置爲1MB。我有它在5MB，它仍然只寫1MB的<。即使在1MB，它仍然只寫902字節。

EDIT2：我已經發布了一些處理接收數據的CLIENT端的代碼。

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，read的JavaDoc：

讀取從輸入流的字節，並將它們存儲一些數成 緩衝區數組b中。實際讀取的字節數作爲整數返回爲 。此方法阻塞，直到輸入數據可用，檢測到文件末尾 或引發異常。

由於源是一個套接字，即使緩衝區大小爲1 MByte，返回的字節數也可能會比預期的要少，因此返回的902 KB字節正常。你必須循環直到流結束。

下面的方法讀取所有字節，比通話監聽：

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); 

正如你所看到的，很多再分配的發生：你必須重新設計你的協議先發送文件的大小和分配一次接收緩衝區。

Answer 2

你讀緩衝區設置爲空讀完前：

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

這將導致一個NullPointerException，你的代碼將關閉套接字。