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，若是上传较大文件会致使内存溢出。若是用TCP协议Socket方式上传就会解决这种弊端。

HTTP协议HttpURLConnection

1. 经过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.咱们能够使用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以前的数据
  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");

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

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

  // 因为HttpURLConnection中会缓存数据, 上传较大文件时会致使内存溢出, 因此咱们使用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"));     //建立目录     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(")));      }    } catch (Exception e) {     e.printStackTrace();    }   else {    System.out.println(request.getMethod());    System.out.println(request.getParameter("username"));    System.out.println(request.getParameter("password"));   }  } }