使用 Retrofit2 将文件上传到 AWS S3 预签名 URL [英] Upload a file to AWS S3 pre-signed URL using Retrofit2

问题描述

我正在尝试使用预签名 URL 将文件上传到 Amazon 的 S3.我从生成 URL 的服务器获取 URL &将它作为 JSON 对象的一部分发送给我.我以字符串形式获取 URL，如下所示:

I'm trying to upload a file to Amazon's S3 using a pre-signed URL. I get the URL from a server which generates the URL & sends it to me as part of a JSON object. I get the URL as a String, something like this:

https://com-example-mysite.s3-us-east-1.amazonaws.com/userFolder/ImageName?X-Amz-Security-Token=xxfooxx%2F%2F%2F%2F%2F%2F%2F%2F%2F%2Fxxbarxx%3D&X-Amz-Algorithm=xxAlgoxx&X-Amz-Date=20170831T090152Z&X-Amz-SignedHeaderhost&X-Amz-Expires=3600&X-Amz-Credential=xxcredxx&X-Amz-Signature=xxsignxx

不幸的是，当我将它传递给 Retrofit2 时，它会修改 String 以使其成为 URL.我已经设置了 encoding=true ，它解决了大部分问题，但并没有完全解决.我知道字符串按原样工作.我已经在 Postman & 中试过了获得成功的响应.

Unfortunately, when I pass this to Retrofit2, it modifies the String attempting to make it into a URL. I've set encoding=true which took care of most of the problem but not completely. I know the String works as it is. I've tried it in Postman & get a successful response.

首先，我尝试将字符串(除了我切出的 baseUrl 之外)作为一个整体放入路径

1st I tried just putting the String (except for what I cut out as baseUrl) as a whole into the Path

public interface UpdateImageInterface {
    @PUT("{url}")
    Call<Void> updateImage(@Path(value="url", encoded=true) String url, Body RequestBody image);
}

调用代码:

    Retrofit retrofit = new Retrofit.Builder()
            .baseUrl("https://com-example-mysite.s3-us-east-1.amazonaws.com/userFolder/")
            .build();

    UpdateImageInterface imageInterface = retrofit.create(UpdateImageInterface.class);
    // imageUrl is "ImageName..."
    Call<Void> call = imageInterface.updateImage(imageUrl, requestFile);

除了?"之外，这大部分都有效(在ImageName"之后)转换为%3F".这会导致错误请求/400.

This works mostly except the the '?' (after "ImageName") get converted to "%3F". This causes a Bad Request / 400.

我的下一次尝试是使用 Retrofit2 创建一个查询，然后将整个字符串(带有多个查询)转储到查询中.

My next attempt was to create a query with Retrofit2 but then dump the whole String (with multiple queries) into the query.

public interface UpdateImageInterface {
    @PUT("ImageName")
    Call<Void> updateProfilePhoto(@Query(value="X-Amz-Security-Token", encoded = true) String token, @Body RequestBody image);
}

调用代码:

    Retrofit retrofit = new Retrofit.Builder()
            .baseUrl("https://com-example-mysite.s3-us-east-1.amazonaws.com/userFolder/")
            .build();

    UpdateImageInterface imageInterface = retrofit.create(UpdateImageInterface.class);
    // imageUrl is "xxfooxx..."
    Call<Void> call = imageInterface.updateImage(imageUrl, requestFile);

这得到'?'正确呈现，但所有的&"更改为%26"

This gets the '?' rendered correctly but all of the '&' get changed to "%26"

最后，我尝试在 baseUrl() 中传递整个字符串，但由于末尾没有 '/' 会导致 IllegalArgumentException.

Lastly I tried passing the whole String in baseUrl() but that gives an IllegalArgumentException for not having '/' on the end.

我知道我可以解析预先签名的 URL 以进行多个查询 &在 Retrofit2 中组装它们，因为应该完成查询，但我想避免这种处理.

I know that I could parse the pre-signed URL to make multiple queries & assemble them in Retrofit2 as queries should be done but I'd like to avoid that processing.

重申问题:

有没有一种方法可以使用 Retrofit2 使用预签名 URL 轻松(无需大量字符串解析)将文件上传到 S3?

Is there a way to easily (without heavy String parsing) upload a file to S3 with a pre-signed URL using Retrofit2?

推荐答案

在同事的帮助下，这是解决方案.

With help from a colleague, this is the solution.

public interface UpdateImageInterface {
    @PUT
    Call<Void> updateImage(@Url String url, @Body RequestBody image);
}

调用代码:

    String CONTENT_IMAGE = "image/jpeg";

    File file = new File(localPhotoPath);    // create new file on device
    RequestBody requestFile = RequestBody.create(MediaType.parse(CONTENT_IMAGE), file);

    /* since the pre-signed URL from S3 contains a host, this dummy URL will
     * be replaced completely by the pre-signed URL.  (I'm using baseURl(String) here
     * but see baseUrl(okhttp3.HttpUrl) in Javadoc for how base URLs are handled
     */
    Retrofit retrofit = new Retrofit.Builder()
        .baseUrl("http://www.dummy.com/")
        .build();

    UpdateImageInterface imageInterface = retrofit.create(UpdateImageInterface.class);
    // imageUrl is the String as received from AWS S3
    Call<Void> call = imageInterface.updateImage(imageUrl, requestFile);

Javadoc 有关 @Url 的信息(类网址) &baseUrl()(类 Retrofit.Builder)

Javadoc for info on @Url (class Url) & baseUrl() (class Retrofit.Builder)

MediaType 是OkHttp 库中经常使用的一个类与改造(均来自 Square).可以在 Javadoc 中找到有关传递给 parse 方法的常量的信息.

MediaType is a class in the OkHttp library that is often used with Retrofit (both from Square). Info about constants passed to the parse method can be found in the Javadoc.

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