Add support for paging and sorting on GridFSTemplate [DATAMONGO-765]

[spring-projects-issues]

Benjamin M opened DATAMONGO-765 and commented

I wondered why GridFsOperations' find methods won't return Page<...>. Or is there another way to get this done?

Additionally I tried to to pass a Pageable object into my Query which doesn't work. Also the limit(...) method and with(new Sort(...)) methods won't work.

Here's my code:

List<GridFSFBFile> files = operations.find(new Query().limit(5));
List<GridFSDBFile> files = operations.find(new Query().with(pageable));
List<GridFSDBFile> files = operations.find(new Query().with(new Sort(Direction.DESC, "uploadDate")));
List<GridFSDBFile> files = operations.find(new Query().with(new Sort(new Sort.Order(Direction.ASC, "uploadDate"))));

All of those queries return the same objects in the same order

---

Affects: 1.3.1

Issue Links:

• DATAMONGO-2411 gridFsTemplate does not consider skip/limit parameters
  ("is duplicated by")
• DATAMONGO-1119 Querying GridFS gives exception under certain circumstances
  ("supersedes")

Referenced from: pull request #806

3 votes, 8 watchers

[spring-projects-issues]

Oliver Drotbohm commented

The reason for this is quite simple: currently we're using the Java driver's GridFS instance directly and it doesn't expose the necessary API needed for paging (counting the files matching a query).

After a brief look I've noticed that GridFS seems to be quite open for extension, so we could theoretically subclass it and add the necessary methods

[spring-projects-issues]

Benjamin M commented

Thanks for the quick response. And what about the Query no limiting/sorting?

BTW: Is it possible to create a normal MongoRepository to access the GridFS contents? (just id, filename, etc. without the file blob itself)

[spring-projects-issues]

Benjamin M commented

I've answered my question from above myself. So maybe you could just provide some GridFSDocument and some GridFSRepository. I've created (only for testing):

@Document(collection="fs.files")
public class GridFSDocument {
@Id
public ObjectId id;
@Field
public String filename;
@Field
public Date uploadDate;
}

public interface GridFSRepository extends MongoRepository<GridFSDocument, ObjectId>{}

Now I can query everything I want to, including Pageable, Sort, limit().... Where are the negative aspects?
The only thing I can't do, is getting the InputStream, but that's not necessary for my current use case

[spring-projects-issues]

Oliver Moser commented

what works for me is simply using a mongoTemplate instance instead:

List<GridFSDBFile> gridFsFiles = mongoTemplate.find(query, GridFSDBFile.class, "fs.files");

which also gives me access to the inputStream of the stored file

[spring-projects-issues]

Oliver Moser commented

\
I realized that using mongoTemplate instead is not enough since there is no associated GridFS instance in this case. So, what you can do is wrap the GridFSDBFile you're working with in something like the following:
\

package com.mongodb.gridfs;

public class GridFSDBFileWrapper extends GridFSDBFile {

    public GridFSDBFileWrapper (GridFSDBFile file, GridFS fs) {
        this._aliases = file._aliases;
        this._chunkSize = file._chunkSize;
        this._contentType = file._contentType;
        this._extradata = file._extradata;
        this._filename = file._filename;
        this._fs = fs;
        this._id = file._id;
        this._length = file._length;
        this._md5 = file._md5;
        this._uploadDate = file._uploadDate;
    }
}

you can autowire the mongoDbFactory instance in your service class and then wrap the instances returned by the mongoTemplate like this
\

private GridFSDBFile wrapGridFSDBFile(GridFSDBFile file) {
        DB db = mongoDbFactory.getDb();
        return new GridFSDBFileWrapper(file, new GridFS(db));
}

hope it helps

[spring-projects-issues]

Mark Paluch commented

Since we switched to Document API we can benefit from GridFSFindIterable.sort/skip/collation and introduce a proper API to query GridFSFile