OkHttp上传文件，服务器端请求解析找不到文件信息的问题

长话短说，不深入解释了，官方给的上传案例代码：

private static final String IMGUR_CLIENT_ID = "...";
  private static final MediaType MEDIA_TYPE_PNG = MediaType.parse("image/png");

  private final OkHttpClient client = new OkHttpClient();

  public void run() throws Exception {
    // Use the imgur image upload API as documented at https://api.imgur.com/endpoints/image
    RequestBody requestBody = new MultipartBuilder()
        .type(MultipartBuilder.FORM)
        .addPart(
            Headers.of("Content-Disposition", "form-data; name="title""),
            RequestBody.create(null, "Square Logo"))
        .addPart(
            Headers.of("Content-Disposition", "form-data; name="image""),
            RequestBody.create(MEDIA_TYPE_PNG, new File("website/static/logo-square.png")))
        .build();

    Request request = new Request.Builder()
        .header("Authorization", "Client-ID " + IMGUR_CLIENT_ID)
        .url("https://api.imgur.com/3/image")
        .post(requestBody)
        .build();

    Response response = client.newCall(request).execute();
    if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);

    System.out.println(response.body().string());
  }

上面这个代码上传文件在Java服务器端用spring boot的 MultiPart解析不到上传的文件，用Python Django，问题亦然。

找到了一个泡网同学的代码：

做了改动1：

RequestBody requestBody = new MultipartBuilder()
                .type(MultipartBuilder.FORM)
                .addPart(
                        Headers.of("Content-Disposition", "form-data; name="UserId""),
                        RequestBody.create(null, UserId))
                .addPart(
                        Headers.of("Content-Disposition", "form-data; name="SecurityCode""),
                        RequestBody.create(null, SecurityCode))
                .addPart(
                        Headers.of("Content-Disposition", "form-data; name="File"; filename ="avatar_upload.jpg""),
                        RequestBody.create(MediaType.parse("image/jpeg"), file))


                .build();

改为以上代码后，Django请求解析可以找到文件了，Spring boot的multipart任然找不到文件信息。

改动1的改动点是：文件的Header信息里面必须有上传文件的名字，当然这个名字其实是随便起的，一般后缀保持正确即可。

这个时候不得不再参考泡网同学的代码，做了修改2：

RequestBody requestBody = new MultipartBuilder()
                .type(MultipartBuilder.FORM)
                .addPart(
                        Headers.of("Content-Disposition", "form-data; name="UserId""),
                        RequestBody.create(null, UserId))
                .addPart(
                        Headers.of("Content-Disposition", "form-data; name="SecurityCode""),
                        RequestBody.create(null, SecurityCode))
                .addPart(
                        Headers.of("Content-Disposition", "form-data; name="File"; filename ="avatar_upload.jpg""),
                        RequestBody.create(MediaType.parse("application/octet-stream"), file))

                .build();

 这回Spring Boot multipart 依旧找不到文件信息了，这回的改动点是把mime类型由图片类型"image/jpeg"改成了附件类型：

"application/octet-stream"

 最后借鉴StackOverFlow的某贴的代码：http://stackoverflow.com/questions/30707681/multipart-file-upload-with-okhttp-spring，

RequestBody body = new MultipartBuilder()
    .addFormDataPart("qqfile", filename, RequestBody.create(MediaType.parse("media/type"), new File(filename)))
    .type(MultipartBuilder.FORM)
    .build();

Request request = new Request.Builder()
    .url("/path/to/your/upload")
    .post(body)
    .build();

OkHttpClient client = new OkHttpClient();
Response response = client.newCall(request).execute();

因为这个帖子的topic就是解决Spring MultiPart的问题，最后终于可以上传了，修改点在于彻底修改了添加文件使用的函数接口，我在build gradle里面已经准备用Apache HttpClient了。

OkHttp有点坑爹啊。

参考：

https://github.com/square/okhttp/wiki/Recipes

http://www.jcodecraeer.com/a/anzhuokaifa/androidkaifa/2015/0824/3355.html