通过Socket方式上传文件后服务器迟迟不返回文件保存路径

最近，项目中遇到一个问题：通过Socket方式上传头像到服务器后，读取服务器的返回数据时要等待很久，导致用户体验非常差。但是这个问题在ios手机端却不存在，因为ios采取的http文件上传方式。一开始我纠结于为何服务器迟迟没有返回文件的位置，手机客户端已经将文件上传完了呀？

我的代码是这样滴（请关注文件上传完成后处理）：

public static String post(String path, Map params, FormFile[] files) throws Exception {
		final String BOUNDARY = "---------------------------7da2137580612"; // 数据分隔线
		final String endline = "--" + BOUNDARY + "--\r\n";// 数据结束标志
		final int BUFFER_SIZE = 1024 * 1024;
		int fileDataLength = 0;
		for (FormFile uploadFile : files) {// 得到文件类型数据的总长度
			StringBuilder fileExplain = new StringBuilder();
			fileExplain.append("--");
			fileExplain.append(BOUNDARY);
			fileExplain.append("\r\n");
			fileExplain.append("Content-Disposition: form-data;name=\"" + uploadFile.getParameterName()
					+ "\";filename=\"" + uploadFile.getFilname() + "\"\r\n");
			fileExplain.append("Content-Type: " + uploadFile.getContentType() + "\r\n\r\n");
			fileExplain.append("\r\n");
			fileDataLength += fileExplain.length();
			if (uploadFile.getInStream() != null) {
				fileDataLength += uploadFile.getFile().length();
			} else {
				fileDataLength += uploadFile.getData().length;
			}
		}
		StringBuilder textEntity = new StringBuilder();
		for (Map.Entry entry : params.entrySet()) {// 构造文本类型参数的实体数据
			textEntity.append("--");
			textEntity.append(BOUNDARY);
			textEntity.append("\r\n");
			textEntity.append("Content-Disposition: form-data; name=\"" + entry.getKey() + "\"\r\n\r\n");
			textEntity.append(entry.getValue());
			textEntity.append("\r\n");
		}
		// 计算传输给服务器的实体数据总长度
		int dataLength = textEntity.toString().getBytes().length + fileDataLength + endline.getBytes().length;

		URL url = new URL(path);
		int port = url.getPort() == -1 ? 80 : url.getPort();
		Socket socket = new Socket(InetAddress.getByName(url.getHost()), port);
		OutputStream outStream = socket.getOutputStream();
		// 下面完成HTTP请求头的发送
		String requestmethod = "POST " + url.getPath() + " HTTP/1.1\r\n";
		outStream.write(requestmethod.getBytes());
		String accept = "Accept: image/gif, image/jpeg, image/pjpeg, text/plain, application/x-shockwave-flash, application/xaml+xml, application/vnd.ms-xpsdocument, application/x-ms-xbap, application/x-ms-application, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, */*\r\n";
		outStream.write(accept.getBytes());
		String language = "Accept-Language: zh-CN\r\n";
		outStream.write(language.getBytes());
		String contenttype = "Content-Type: multipart/form-data; boundary=" + BOUNDARY + "\r\n";
		outStream.write(contenttype.getBytes());
		String contentlength = "Content-Length: " + dataLength + "\r\n";
		outStream.write(contentlength.getBytes());
		String alive = "Connection: Keep-Alive\r\n";
		outStream.write(alive.getBytes());
		String host = "Host: " + url.getHost() + ":" + port + "\r\n";
		outStream.write(host.getBytes());
		// 写完HTTP请求头后根据HTTP协议再写一个回车换行
		outStream.write("\r\n".getBytes());
		// 把所有文本类型的实体数据发送出来
		outStream.write(textEntity.toString().getBytes());
		// 把所有文件类型的实体数据发送出来
		for (FormFile uploadFile : files) {
			StringBuilder fileEntity = new StringBuilder();
			fileEntity.append("--");
			fileEntity.append(BOUNDARY);
			fileEntity.append("\r\n");
			fileEntity.append("Content-Disposition: form-data;name=\"" + uploadFile.getParameterName()
					+ "\";filename=\"" + uploadFile.getFilname() + "\"\r\n");
			fileEntity.append("Content-Type: " + uploadFile.getContentType() + "\r\n\r\n");
			outStream.write(fileEntity.toString().getBytes());
			if (uploadFile.getInStream() != null) {
				byte[] buffer = new byte[1024];
				int len = 0;
				while ((len = uploadFile.getInStream().read(buffer, 0, 1024)) != -1) {
					outStream.write(buffer, 0, len);
				}
				uploadFile.getInStream().close();
			} else {
				outStream.write(uploadFile.getData(), 0, uploadFile.getData().length);
			}
			outStream.write("\r\n".getBytes());
		}
		// 下面发送数据结束标志，表示数据已经结束
		outStream.write(endline.getBytes());
		
		BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
		if (reader.readLine().indexOf("200") == -1) {// 读取web服务器返回的数据，判断请求码是否为200，如果不是200，代表请求失败
			return null;
		}
		
		char[] data = new char[BUFFER_SIZE];
		int len = -1;
                String responseMsg = null;
                while((len = reader.read(data)) != -1)
                {
                  responseMsg += String.valueOf(data, 0, len);
                }
		
		outStream.flush();
		outStream.close();
		reader.close();
		socket.close();
		LogUtil.d("SocketHttpUpload/ post() response: " + responseMsg);
		return responseMsg;
	}

通过debug跟踪发现，第一次执行

 while((len = reader.read(data)) != -1)
                {
                  responseMsg += String.valueOf(data, 0, len);
                }

responseMsg就已经得到了文件的地址，但是第二次执行reader.read(data) 时却卡住了，过了很长时间才读到数据-1，为何呢？感觉就是服务器向客户端写数据结束了，却没告诉客户端已经写结束了，所以就开始怀疑服务器代码有问题，可是为何ios却没这个问题呢？无奈之下，只能继续从自身找原因了。幸好看到了这个博客 android通过socket发送大文件到服务器并返回结果，找到了问题的原因才得以解决。 原来socket.getOutputStream()传送完文件后，需要关闭socket的OutputStream(socket.shutdownOutput();),如果不关闭客户端的输出流，那么服务器端socket获取输入流对象后，调用这个对象的read方法会在执行完后一直处于等待状态，也就是read阻塞。

修改后代码如下：

		//省略部分代码
		...........
		
		
		// 下面发送数据结束标志，表示数据已经结束
		outStream.write(endline.getBytes());
		outStream.flush();  
        // 一定要加上这句，否则收不到来自服务器端的消息返回  
        socket.shutdownOutput();  
		BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
		if (reader.readLine().indexOf("200") == -1) {// 读取web服务器返回的数据，判断请求码是否为200，如果不是200，代表请求失败
			return null;
		}
		
		char[] data = new char[BUFFER_SIZE];
		
		int len = -1;
		String responseMsg = null;
		while((len = reader.read(data)) != -1)
		{
			responseMsg += String.valueOf(data, 0, len);
		}
		
		
		//省略部分代码
		...........