Android分别使用HTTP协议和TCP协议实现上传文件

Android上传文件有两种方式，第一种是基于Http协议的HttpURLConnection，第二种是基于TCP协议的Socket。 这两种方式的区别是使用HttpURLConnection上传时内部有缓存机制，如果上传较大文件会导致内存溢出。如果用TCP协议Socket方式上传就会解决这种弊端。

HTTP协议HttpURLConnection

1. 通过URL封装路径打开一个HttpURLConnection

2.设置请求方式以及头字段：Content-Type、Content-Length、Host

3.拼接数据发送

示例：

	private static final String BOUNDARY = "---------------------------7db1c523809b2";//数据分割线

	public boolean uploadHttpURLConnection(String username, String password, String path) throws Exception {
		//找到sdcard上的文件
		File file = new File(Environment.getExternalStorageDirectory(), path);
                  //仿Http协议发送数据方式进行拼接
		StringBuilder sb = new StringBuilder();
		sb.append("--" + BOUNDARY + "\r\n");
		sb.append("Content-Disposition: form-data; name=\"username\"" + "\r\n");
		sb.append("\r\n");
		sb.append(username + "\r\n");

		sb.append("--" + BOUNDARY + "\r\n");
		sb.append("Content-Disposition: form-data; name=\"password\"" + "\r\n");
		sb.append("\r\n");
		sb.append(password + "\r\n");

		sb.append("--" + BOUNDARY + "\r\n");
		sb.append("Content-Disposition: form-data; name=\"file\"; filename=\"" + path + "\"" + "\r\n");
		sb.append("Content-Type: image/pjpeg" + "\r\n");
		sb.append("\r\n");

		byte[] before = sb.toString().getBytes("UTF-8");
		byte[] after = ("\r\n--" + BOUNDARY + "--\r\n").getBytes("UTF-8");

		URL url = new URL("http://192.168.1.16:8080/14_Web/servlet/LoginServlet");
		HttpURLConnection conn = (HttpURLConnection) url.openConnection();
		conn.setRequestMethod("POST");
		conn.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + BOUNDARY);
		conn.setRequestProperty("Content-Length", String.valueOf(before.length + file.length() + after.length));
		conn.setRequestProperty("HOST", "192.168.1.16:8080");
		conn.setDoOutput(true);	

		OutputStream out = conn.getOutputStream();
		InputStream in = new FileInputStream(file);
		
		out.write(before);

		byte[] buf = new byte[1024];
		int len;
		while ((len = in.read(buf)) != -1)
			out.write(buf, 0, len);

		out.write(after);

		in.close();
		out.close();
		return conn.getResponseCode() == 200;
	}

TCP协议Socket

1.我们可以使用Socket发送TCP请求，将上传数据分段发送

示例：

	public boolean uploadBySocket(String username, String password, String path) throws Exception {
		// 根据path找到SDCard中的文件
		File file = new File(Environment.getExternalStorageDirectory(), path);
		// 组装表单字段和文件之前的数据
		StringBuilder sb = new StringBuilder();

		sb.append("--" + BOUNDARY + "\r\n");
		sb.append("Content-Disposition: form-data; name=\"username\"" + "\r\n");
		sb.append("\r\n");
		sb.append(username + "\r\n");

		sb.append("--" + BOUNDARY + "\r\n");
		sb.append("Content-Disposition: form-data; name=\"password\"" + "\r\n");
		sb.append("\r\n");
		sb.append(password + "\r\n");

		sb.append("--" + BOUNDARY + "\r\n");
		sb.append("Content-Disposition: form-data; name=\"file\"; filename=\"" + path + "\"" + "\r\n");
		sb.append("Content-Type: image/pjpeg" + "\r\n");
		sb.append("\r\n");

		// 文件之前的数据
		byte[] before = sb.toString().getBytes("UTF-8");
		// 文件之后的数据
		byte[] after = ("\r\n--" + BOUNDARY + "--\r\n").getBytes("UTF-8");

		URL url = new URL("http://192.168.1.199:8080/14_Web/servlet/LoginServlet");

		// 由于HttpURLConnection中会缓存数据, 上传较大文件时会导致内存溢出, 所以我们使用Socket传输
		Socket socket = new Socket(url.getHost(), url.getPort());
		OutputStream out = socket.getOutputStream();
		PrintStream ps = new PrintStream(out, true, "UTF-8");

		// 写出请求头
		ps.println("POST /14_Web/servlet/LoginServlet HTTP/1.1");
		ps.println("Content-Type: multipart/form-data; boundary=" + BOUNDARY);
		ps.println("Content-Length: " + String.valueOf(before.length + file.length() + after.length));
		ps.println("Host: 192.168.1.199:8080");
		
		InputStream in = new FileInputStream(file);

		// 写出数据
		out.write(before);

		byte[] buf = new byte[1024];
		int len;
		while ((len = in.read(buf)) != -1)
			out.write(buf, 0, len);

		out.write(after);

		in.close();
		out.close();

		return true;
	}

搭建服务器，完成上传功能

package cn.test.web.servlet;

import java.io.File;
import java.io.IOException;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileItemFactory;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

public class LoginServlet extends HttpServlet {

	private static final long serialVersionUID = 1L;

	@Override
	public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		doPost(request, response);
	}

	@Override
	public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		boolean isMultipart = ServletFileUpload.isMultipartContent(request);
		if (isMultipart)
			try {
				FileItemFactory factory = new DiskFileItemFactory();
				ServletFileUpload upload = new ServletFileUpload(factory);
				List<FileItem> items = upload.parseRequest(request);
				File dir = new File(request.getSession().getServletContext().getRealPath("/WEB-INF/upload"));
				//创建目录
				dir.mkdir();
				for (FileItem item : items)
					if (item.isFormField())
						System.out.println(item.getFieldName() + ": " + item.getString());
					else{
						item.write(new File(dir,item.getName().substring(item.getName().lastIndexOf("\\")+1)));
					}
			} catch (Exception e) {
				e.printStackTrace();
			}
		else {
			System.out.println(request.getMethod());
			System.out.println(request.getParameter("username"));
			System.out.println(request.getParameter("password"));
		}
	}
}