Storing Files with GridFS

About GridFS

With GridFS, MongoDB provides a specification for storing and retrieving files that exceed the document size limit of 16 MB. GridFS uses two collections to store files. One collection stores the file chunks, and the other stores file metadata. More information on GridFS can be found in the MongoDB GridFS documentation.

GridFS files provide the following properties - _id stores the identifier of the file. By default, it uses a BSON ObjectId, although you can override this in the mapping. - chunkSize stores the size of a single chunk in bytes. By default, chunks are 261120 bytes (i.e. 255 KiB) in size. - filename is the name of the file as assigned. Note that filenames don't need to be unique: instead, multiple files with the same name are treated as revisions of that same file, with the last file uploaded being the latest revision. - length stores the size of the file in bytes. - metadata is an optional embedded document that can be used to store additional data along with the file. - uploadDate stores the date when the file was originally persisted to the GridFS bucket. It is also used to track revisions of multiple files with the same filename.

Mapping documents as GridFS files

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<?php

namespace Documents;

use Doctrine\ODM\MongoDB\Mapping\Annotations\File;
use Doctrine\ODM\MongoDB\Mapping\Annotations\Id;

/** @File(bucketName='image') */
class Image
{
    /** @Id */
    private $id;

    /** @File\Filename */
    private $name;

    /** @File\UploadDate */
    private $uploadDate;

    /** @File\Length */
    private $length;

    /** @File\ChunkSize */
    private $chunkSize;

    /** @File\Metadata(targetDocument=ImageMetadata::class) */
    private $metadata;

    public function getId(): ?string
    {
        return $this->id;
    }

    public function getName(): ?string
    {
        return $this->name;
    }

    public function getChunkSize(): ?int
    {
        return $this->chunkSize;
    }

    public function getLength(): ?int
    {
        return $this->length;
    }

    public function getUploadDate(): \DateTimeInterface
    {
        return $this->uploadDate;
    }

    public function getMetadata(): ?ImageMetadata
    {
        return $this->metadata;
    }
}
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If you would rather use XML to map metadata, the corresponding mapping would look like this:

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<?xml version="1.0" encoding="UTF-8"?>

<doctrine-mongo-mapping xmlns="http://doctrine-project.org/schemas/odm/doctrine-mongo-mapping"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://doctrine-project.org/schemas/odm/doctrine-mongo-mapping
    http://doctrine-project.org/schemas/odm/doctrine-mongo-mapping.xsd">

    <gridfs-file name="Documents\Image">
        <id />
        <length />
        <chunk-size />
        <upload-date />
        <filename field-name="name" />

        <metadata target-document="Documents\ImageMetadata" />
    </gridfs-file>
</doctrine-mongo-mapping>
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With XML mappings, the fields are automatically mapped to camel-cased properties. To change property names, simply override the fieldName attribute for each field. You cannot override any other options for GridFS fields.

The ImageMetadata class must be an embedded document:

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<?php

namespace Documents;

use Doctrine\ODM\MongoDB\Mapping\Annotations\EmbeddedDocument;
use Doctrine\ODM\MongoDB\Mapping\Annotations\Field;

/** @EmbeddedDocument */
class ImageMetadata
{
    /** @Field(type="string") */
    private $contentType;

    public function __construct(string $contentType)
    {
        $this->contentType = $contentType;
    }

    public function getContentType(): ?string
    {
        return $this->contentType;
    }
}
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Inserting files into GridFS buckets

To insert a new file, you have to upload its contents using the repository. You have the option to upload contents from a file or a stream. Alternatively, you can also open an upload stream and write contents yourself.

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<?php

$repository = $documentManager->getRepository(Documents\Image::class);
$file = $repository->uploadFromFile('/tmp/path/to/image', 'image.jpg');
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When using the default GridFS repository implementation, the uploadFromFile and uploadFromStream methods return a proxy object of the file you just uploaded.

If you want to pass options, such as a metadata object to the uploaded file, you can pass an UploadOptions object as the last argument to the uploadFromFile, uploadFromStream, or openUploadStream method call:

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<?php

use Doctrine\ODM\MongoDB\Repository\UploadOptions;

$uploadOptions = new UploadOptions();
$uploadOptions->metadata = new Documents\ImageMetadata('image/jpeg');
$uploadOptions->chunkSizeBytes = 1024 * 1024;

$repository = $documentManager->getRepository(Documents\Image::class);
$file = $repository->uploadFromFile('/tmp/path/to/image', 'image.jpg', $uploadOptions);
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Reading files from GridFS buckets

When reading GridFS files, they behave like all other documents. You can query for them using the find* methods in the repository, create query or aggregation pipeline builders, and also use them as targetDocument in references. You can access all properties of the file including metadata, but not file content.

The GridFS specification uses streams to deal with file contents. To avoid having this resource overhead every time you fetch a file from the database, file contents are only provided through the downloadToStream repository method. Accessors to provide a stream in the document may be implemented in future versions.

The following code sample puts the file contents into a different file after uploading:

1
<?php

use Doctrine\ODM\MongoDB\Repository\UploadOptions;

$uploadOptions = new UploadOptions();
$uploadOptions->metadata = new Documents\ImageMetadata('image/jpeg');

$repository = $documentManager->getRepository(Documents\Image::class);
$file = $repository->uploadFromFile('/tmp/path/to/image', 'image.jpg', $uploadOptions);

$stream = fopen('tmp/path/to/copy', 'w+');
try {
    $repository->downloadToStream($file->getId(), $stream);
finally {
    fclose($stream);
}
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The downloadToStream method takes the identifier of a file as first argument and a writable stream as the second arguments. If you need to manipulate the file contents before writing it to disk or sending it to the client, consider using a memory stream using the php://memory stream wrapper.

Alternatively, you can also use the openDownloadStream method which returns a stream from where you can read file contents:

1
<?php

use Doctrine\ODM\MongoDB\Repository\UploadOptions;

$uploadOptions = new UploadOptions();
$uploadOptions->metadata = new Documents\ImageMetadata('image/jpeg');

$repository = $documentManager->getRepository(Documents\Image::class);
$file = $repository->uploadFromFile('/tmp/path/to/image', 'image.jpg', $uploadOptions);

$stream = $repository->openDownloadStream($file->getId());
try {
    $contents = stream_get_contents($stream);
finally {
    fclose($stream);
}
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