如何使用Spring Data MongoDB通过GridFS ObjectId获取二进制流 [英] How to get a binary stream by GridFS ObjectId with Spring Data MongoDB

问题描述

当我已经拥有正确的ObjectId时，我不知道如何使用spring-data-mongodb及其GridFSTemplate从GridFS流式传输二进制文件.

I can't figure out how to stream a binary file from GridFS with spring-data-mongodb and its GridFSTemplate when I already have the right ObjectId.

GridFSTemplate返回GridFSResource(getResource())或GridFSFile(findX()).

GridFSTemplate returns either GridFSResource (getResource()) or GridFSFile (findX()).

我可以通过ID获取GridFSFile:

// no way to get the InputStream?
GridFSFile file = gridFsTemplate.findOne(Query.query(Criteria.where("_id").is(id)))

，但是没有明显的方法为该GridFSFile获取InputStream.

but there is no obvious way how to get an InputStream for that GridFSFile.

只有GridFSResource允许我掌握InputStreamResource#getInputstream对应的InputStream.但是获取GridFSResource的唯一方法是通过其filename.

Only GridFSResource allows me to get hold of the corresonding InputStream with InputStreamResource#getInputstream. But the only way to get a GridFSResource is by its filename.

// no way to get GridFSResource by ID?
GridFSResource resource = gridFsTemplate.getResource("test.jpeg");
return resource.getInputStream();

以某种方式GridFsTemplate API意味着文件名是唯一的-不是. GridFsTemplate实现仅返回第一个元素.

Somehow the GridFsTemplate API implies that filenames are unique - which they are not. The GridFsTemplate implementation just returns the first element.

现在我正在使用本机MongoDB API，一切又变得有意义了:

Now I'm using the native MongoDB API and everything makes sense again:

GridFS gridFs = new GridFs(mongo);
GridFSDBFile nativeFile = gridFs.find(blobId);
return nativeFile.getInputStream();

似乎我误解了Spring Data Mongo GridFS抽象背后的基本概念.我希望(至少)以下其中一项可能/正确:

It looks like I'm misunderstanding the fundamental concepts behind the Spring Data Mongo GridFS abstraction. I'd expect (at least) one of the following things to be possible/true:

• 通过其ID获取GridFSResource
• 为我已经拥有的GridFsFile获取GridFSResource或InputStream

• get a GridFSResource by its ID
• get a GridFSResource or InputStream for a GridFsFile I already have

我错了吗?Spring Data MongoDB API的这一特定部分是否有些奇怪?

Am I wrong or is there something odd with this particular piece of the Spring Data MongoDB API?

推荐答案

我也偶然发现了这一点.实际上，令GridFsTemplate如此设计感到非常震惊... 无论如何，到目前为止我的丑陋解决方案":

I stumbled upon this, too. And I am actually pretty shocked that the GridFsTemplate has been designed like this... Anyway, my ugly "solution" to this so far:

public GridFsResource download(String fileId) {
    GridFSFile file = gridFsTemplate.findOne(Query.query(Criteria.where("_id").is(fileId)));

    return new GridFsResource(file, getGridFs().openDownloadStream(file.getObjectId()));
}

private GridFSBucket getGridFs() {

    MongoDatabase db = mongoDbFactory.getDb();
    return GridFSBuckets.create(db);
}

注意:您必须注入MongoDbFactory才能使其工作...

Note: You have to inject the MongoDbFactory for this to work...

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