Android端通过HttpURLConnection上传文件到服务器

一：实现原理

最近在做Android客户端的应用开发，涉及到要把图片上传到后台服务器中，自己选择了做Spring3 MVC HTTP API作为后台上传接口，android客户端我选择用HttpURLConnection来通过form提交文件数据实现上传功能，本来想网上搜搜拷贝一下改改代码就好啦，发现根本没有现成的例子，多数的例子都是基于HttpClient的或者是基于Base64编码以后作为字符串来传输图像数据，于是我不得不自己动手，参考了网上一些资料，最终实现基于HttpURLConnection上传文件的android客户端代码，废话少说，其实基于HttpURLConnection实现文件上传最关键的在于要熟悉Http协议相关知识，知道MIME文件块在Http协议中的格式表示，基本的传输数据格式如下：

其中boundary表示form的边界，只要按照格式把内容字节数写到HttpURLConnection的对象输出流中，服务器端的Spring Controller 就会自动响应接受，跟从浏览器页面上上传文件是一样的。

服务器端HTTP API，我是基于Spring3 MVC实现的Controller，代码如下：

 @RequestMapping(value = "/uploadMyImage/{token}", method = RequestMethod.POST)

 public @ResponseBody String getUploadFile(HttpServletRequest request, HttpServletResponse response,

         @PathVariable String token) {

     logger.info("spring3 MVC upload file with Multipart form");

     logger.info("servlet context path : " + request.getSession().getServletContext().getRealPath("/"));

     UserDto profileDto = userService.getUserByToken(token);

     String imgUUID = "";

     try {

         if (request instanceof MultipartHttpServletRequest && profileDto.getToken() != null) {

             MultipartHttpServletRequest multipartRequest = (MultipartHttpServletRequest) request;

             logger.info("spring3 MVC upload file with Multipart form");

             // does not work, oh my god!!

             MultipartFile file = multipartRequest.getFiles("myfile").get(0);

             InputStream input = file.getInputStream();

             long fileSize = file.getSize();

             BufferedImage image = ImageIO.read(input);

             // create data transfer object

             ImageDto dto = new ImageDto();

             dto.setCreateDate(new Date());

             dto.setFileName(file.getOriginalFilename());

             dto.setImage(image);

             dto.setCreator(profileDto.getUserName());

             dto.setFileSize(fileSize);

             dto.setType(ImageAttachmentType.CLIENT_TYPE.getTitle());

             dto.setUuid(UUID.randomUUID().toString());

             /// save to DB

             imgUUID = imageService.createImage(dto);

             input.close();

         }

     } catch (Exception e) {

         e.printStackTrace();

         logger.error("upload image error", e);

     }

     return imgUUID;

 }

Android客户端基于HttpURLConnection实现上传的代码，我把它封装成一个单独的类文件，这样大家可以直接使用，只要传入上传的URL等参数即可。代码如下：

package com.demo.http;

import java.io.BufferedInputStream;

import java.io.DataOutputStream;

import java.io.File;

import java.io.FileInputStream;

import java.io.IOException;

import java.io.InputStream;

import java.net.HttpURLConnection;

import java.net.URL;

import java.util.Random;

import android.os.Handler;

import android.util.Base64;

import android.util.Log;

public class UploadImageTask implements APIURLConstants {

    private String requestURL = DOMAIN_ADDRESS + UPLOAD_DESIGN_IMAGE_URL; // default

    private final String CRLF = "\r\n";

    private Handler handler;

    private String token;

    public UploadImageTask(String token, Handler handler) {

        this.handler = handler;

        this.token = token;

    }

    public String execute(File...files) {

        InputStream inputStream = null;

        HttpURLConnection urlConnection = null;

        FileInputStream fileInput = null;

        DataOutputStream requestStream = null;

        handler.sendEmptyMessage(50);

        try {

            // open connection

            URL url = new URL(requestURL.replace("{token}", this.token));

            urlConnection = (HttpURLConnection) url.openConnection();

            // create random boundary

            Random random = new Random();

            byte[] randomBytes = new byte[16];

            random.nextBytes(randomBytes);

            String boundary = Base64.encodeToString(randomBytes, Base64.NO_WRAP);

            /* for POST request */

            urlConnection.setDoOutput(true);

            urlConnection.setDoInput(true);

            urlConnection.setUseCaches(false);

            urlConnection.setRequestMethod("POST");

            long size = (files[0].length() / 1024);

            if(size >= 1000) {

                handler.sendEmptyMessage(-150);

                return "error";

            }

            // 构建Entity form

            urlConnection.setRequestProperty("Connection", "Keep-Alive");

            urlConnection.setRequestProperty("Content-Type", "multipart/form-data;boundary=" + boundary);

            urlConnection.setRequestProperty("Cache-Control", "no-cache");

            // never try to chunked mode, you need to set a lot of things

            //  if(size > 400) {

            //      urlConnection.setChunkedStreamingMode(0);

            //  }

            //  else {

            //      urlConnection.setFixedLengthStreamingMode((int)files[0].length());

            //  }

            // end comment by zhigang on 2016-01-19

            /* upload file stream */

            fileInput = new FileInputStream(files[0]);

            requestStream = new DataOutputStream(urlConnection.getOutputStream());

            String nikeName = "myfile";

            requestStream = new DataOutputStream(urlConnection.getOutputStream());

            requestStream.writeBytes("--" + boundary + CRLF);

            requestStream.writeBytes("Content-Disposition: form-data; name=\"" + nikeName + "\"; filename=\"" + files[0].getName() + "\""+ CRLF);

            requestStream.writeBytes("Content-Type: " + getMIMEType(files[0]) + CRLF);

            requestStream.writeBytes(CRLF);

            // 写图像字节内容

            int bytesRead;

            byte[] buffer = new byte[8192];

            handler.sendEmptyMessage(50);

            while((bytesRead = fileInput.read(buffer)) != -1) {

                requestStream.write(buffer, 0, bytesRead);

            }

            requestStream.flush();

            requestStream.writeBytes(CRLF);

            requestStream.flush();

            requestStream.writeBytes("--" + boundary + "--" + CRLF);

            requestStream.flush();

            fileInput.close();

            // try to get response

            int statusCode = urlConnection.getResponseCode();

            if (statusCode == 200) {

                inputStream = new BufferedInputStream(urlConnection.getInputStream());

                String imageuuId = HttpUtil.convertInputStreamToString(inputStream);

                Log.i("image-uuid", "uploaded image uuid : " + imageuuId);

                handler.sendEmptyMessage(50);

                return imageuuId;

            }

        } catch (Exception e) {

            e.printStackTrace();

        } finally {

            if (inputStream != null) {

                try {

                    inputStream.close();

                } catch (IOException e) {

                    e.printStackTrace();

                }

            }

            if(requestStream != null) {

                try {

                    requestStream.close();

                } catch (IOException e) {

                    e.printStackTrace();

                }

            }

            if(fileInput != null) {

                try {

                    fileInput.close();

                } catch (IOException e) {

                    e.printStackTrace();

                }

            }

            if (urlConnection != null) {

                urlConnection.disconnect();

            }

        }

        handler.sendEmptyMessage(50);

        return null;

    }

    private String getMIMEType(File file) {

        String fileName = file.getName();

        if(fileName.endsWith("png") || fileName.endsWith("PNG")) {

            return "image/png";

        }

        else {

            return "image/jpg";

        }

    }

}

巴特西

Android端通过HttpURLConnection上传文件到服务器

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