Android 程序使用http上传文件

Android程序使用http上传文件

有时，在网络编程过程中需要向服务器上传文件。Multipart/form-data是上传文件的一种方式。

Multipart/form-data其实就是浏览器用表单上传文件的方式。最常见的情境是：在写邮件时，向邮件后添加附件，附件通常使用表单添加，也就是用multipart/form-data格式上传到服务器。

<form action=“/TestWeb/command=UpdatePicture” method=”post” enctype=”multipart/form-data”>
	<input type=”file” name=”uploadfile1”/><br>
	<input type=”file” name=”uploadfile2”/><br>
	<input type=”submit” value=”uploadfile”>
</form>

内容如下：
Type：multipart/form-data; boundary=-----------------------------265001916915724
-----------------------------265001916915724
Content-Disposition: form-data; name="uploadfile1"; filename="web.txt"
Content-Type: text/plain

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默认网关0.0.0.0 即本机

-----------------------------265001916915724
Content-Disposition: form-data; name="uploadfile2"; filename="20080116064637581.jpg"
Content-Type: image/jpeg

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-----------------------------265001916915724—


注意点一：
      Header 下面boundary 有27个 -（横杆）
      POST Data 下面传输每个文件的开头是有29个 -
注意点二：
      观察POST Data可以发现从第一个-----------------------------265001916915724
      到第二个-----------------------------265001916915724之间为一个txt文件的相关
      信息。
上面form提交的servlet不用实现，只是解析了http协议，为下面模拟铺垫。

下面实现android客户端上传图片到服务端的servlet
android客户端代码

public void upload() {
        Log.d(TAG, "upload begin");
        HttpURLConnection connection = null;
        DataOutputStream dos = null;
        FileInputStream fin = null;
        
        String boundary = "---------------------------265001916915724";
        // 真机调试的话，这里url需要改成电脑ip
        // 模拟机用10.0.0.2,127.0.0.1被tomcat占用了
        String urlServer = "http://10.0.0.2:8080/TestWeb/command=UpdatePicture";
        String lineEnd = "\r\n";
        String pathOfPicture = "/sdcard/aaa.jpg";
        int bytesAvailable, bufferSize, bytesRead;
        int maxBufferSize = 1*1024*512;
        byte[] buffer = null;
        
        try {
            Log.d(TAG, "try");
            URL url = new URL(urlServer);
            connection = (HttpURLConnection) url.openConnection();
            
            // 允许向url流中读写数据
            connection.setDoInput(true);
            connection.setDoOutput(true);
            connection.setUseCaches(true);
            
            // 启动post方法
            connection.setRequestMethod("POST");
            
            // 设置请求头内容
            connection.setRequestProperty("connection", "Keep-Alive");
            connection.setRequestProperty("Content-Type", "text/plain");
            
            // 伪造请求头
            connection.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + boundary);
          
           
            // 开始伪造POST Data里面的数据
            dos = new DataOutputStream(connection.getOutputStream());
            fin = new FileInputStream(pathOfPicture);
            
            Log.d(TAG, "开始上传images");
            //--------------------开始伪造上传images.jpg的信息-----------------------------------
            String fileMeta = "--" + boundary + lineEnd +
                            "Content-Disposition: form-data; name=\"uploadedPicture\"; filename=\"" + pathOfPicture + "\"" + lineEnd +
                            "Content-Type: image/jpeg" + lineEnd + lineEnd;
            // 向流中写入fileMeta
            dos.write(fileMeta.getBytes());
            
            // 取得本地图片的字节流，向url流中写入图片字节流
            bytesAvailable = fin.available();
            bufferSize = Math.min(bytesAvailable, maxBufferSize);
            buffer = new byte[bufferSize];
            
            bytesRead = fin.read(buffer, 0, bufferSize);
            while(bytesRead > 0) {
                dos.write(buffer, 0, bufferSize);
                bytesAvailable = fin.available();
                bufferSize = Math.min(bytesAvailable, maxBufferSize);
                bytesRead = fin.read(buffer, 0, bufferSize);
            }
            dos.writeBytes(lineEnd+lineEnd);
            //--------------------伪造images.jpg信息结束-----------------------------------
            Log.d(TAG, "结束上传");
            
            // POST Data结束
            dos.writeBytes("--" + boundary + "--");
            
            // Server端返回的信息
            System.out.println("" + connection.getResponseCode());
            System.out.println("" + connection.getResponseMessage());
            
            if (dos != null) {
                dos.flush();
                dos.close();
            }
            Log.d(TAG, "upload success-----------------------------------------");
        } catch (Exception e) {
           e.printStackTrace();
           Log.d(TAG, "upload fail");
        }
    }

服务端servlet

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

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

// 利用该组件进行接收客户端上传的文件
// 需要自己加载commons-fileupload-1.2.2.jar和commons-io-2.1.jar
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

/**
 * Servlet implementation class ReceivePictureFromAndroid
 */
@WebServlet("/command=UpdatePicture")
public class ReceivePictureFromAndroid extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    public ReceivePictureFromAndroid() {
        super();
    }

	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            
	    try {
	      DiskFileItemFactory factory = new DiskFileItemFactory();
	      ServletFileUpload upload = new ServletFileUpload(factory);
	      List<FileItem> list = upload.parseRequest(request);
	      System.out.println(list + " list " + list.size() );
	      for(FileItem item : list) {
	          String paramName = item.getFieldName();
	          System.out.println(paramName);
	          String paramValue = item.getString();
	          System.out.println(paramValue);
	          if(item.isFormField() == false) {
	              File f = new File("f:\\img.jpg");
	              item.write(f);
	               System.out.println("write filt success");
	          }
	      }
	    } catch (Exception e) {   
	        e.printStackTrace();
	    }
	}

}