1. Overview
This tutorial will explore one of the core features of Spring Data MongoDB: interacting with GridFS.
The GridFS storage spec is mainly used for working with files that exceed the BSON-document size limit of 16MB. And Spring Data provides a GridFsOperations interface and its implementation – GridFsTemplate – to easily interact with this filesystem.
2. Configuration
2.1. XML Configuration
Let’s start with the simple XML configuration for the GridFsTemplate:
<bean id="gridFsTemplate" class="org.springframework.data.mongodb.gridfs.GridFsTemplate">
<constructor-arg ref="mongoDbFactory" />
<constructor-arg ref="mongoConverter" />
</bean>
The constructor arguments to the GridFsTemplate include bean references to mongoDbFactory, which creates a Mongo database, and mongoConverter, which converts between Java and MongoDB types. Their bean definitions are below.
<mongo:db-factory id="mongoDbFactory" dbname="test" mongo-ref="mongo" />
<mongo:mapping-converter id="mongoConverter" base-package="org.baeldung.converter">
<mongo:custom-converters base-package="org.baeldung.converter"/>
</mongo:mapping-converter>
2.2. Java Configuration
Let’s create a similar configuration, only with Java:
@Bean
public GridFsTemplate gridFsTemplate() throws Exception {
return new GridFsTemplate(mongoDbFactory(), mappingMongoConverter());
}
For this configuration we used mongoDbFactory and mappingMongoConverter from org.springframework.data.mongodb.config.AbstractMongoConfiguration.
3. GridFsTemplate Core Methods
3.1. store
The store method saves a file into MongoDB.
Suppose we have an empty database and wish to store a file in it:
InputStream inputStream = new FileInputStream("src/main/resources/test.png");
String id =
gridFsTemplate.store(inputStream, "test.png", "image/png", metaData).getId().toString();
Note that we can save additional metadata along with the file by passing a DBObject to the store method. For our example, the DBObject might look something like this:
DBObject metaData = new BasicDBObject();
metaData.put("user", "alex");
GridFS uses two collections to store the file metadata and its content. The file’s metadata is stored in the files collection, and the file’s content is stored in the chunks collection. Both collections are prefixed with fs.
If we execute the MongoDB command db[‘fs.files’].find(), we will see the fs.files collection:
{
"_id" : ObjectId("5602de6e5d8bba0d6f2e45e4"),
"metadata" : {
"user" : "alex"
},
"filename" : "test.png",
"aliases" : null,
"chunkSize" : NumberLong(261120),
"uploadDate" : ISODate("2015-09-23T17:16:30.781Z"),
"length" : NumberLong(855),
"contentType" : "image/png",
"md5" : "27c915db9aa031f1b27bb05021b695c6"
}
The command db[‘fs.chunks’].find() retrieves the file’s content:
{
"_id" : ObjectId("5602de6e5d8bba0d6f2e45e4"),
"files_id" : ObjectId("5602de6e5d8bba0d6f2e45e4"),
"n" : 0,
"data" :
{
"$binary" : "/9j/4AAQSkZJRgABAQAAAQABAAD/4QAqRXhpZgAASUkqAAgAAAABADEBAgAHAAAAGgAAAAAAAABHb29nbGUAAP/bAIQAAwICAwICAwMDAwQDAwQFCAUFBAQFCgcHBggM
CgwMCwoLCw0OEhANDhEOCwsQFhARExQVFRUMDxcYFhQYEhQVFAEDBAQGBQUJBgYKDw4MDhQUFA8RDQwMEA0QDA8VDA0NDw0MDw4MDA0ODxAMDQ0MDAwODA8MDQ4NDA0NDAwNDAwQ/8AA
EQgAHAAcAwERAAIRAQMRAf/EABgAAQEBAQEAAAAAAAAAAAAAAAgGBwUE/8QALBAAAgEDAgQFAwUAAAAAAAAAAQIDBAURBiEABwgSIjFBYXEyUYETFEKhw
f/EABoBAAIDAQEAAAAAAAAAAAAAAAMEAQIFBgD/xAAiEQACAgEDBAMAAAAAAAAAAAAAAQIRAyIx8BJRYYETIUH/2gAMAwEAAhEDEQA/AHDyq1Bb6GjFPMAszLkZHHCTi1I6O
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khUPYNOx92vW9PcrdDW0FUJqOp7po5ETIYMxOdyOAK0qAvcgKPWa0oMTo7SEYDKPp98/5wPoJsx3rZ1wLhojS9iinLD9w9W47iSwVe0Z3wfrPoce2eC4I6rCX9MxrpUpWqudNunUosNLR1EkiyIGDqUKF
fyZB+AeG80riueQdVfObC/tN1pLdaLfSxMiRQ08aIg2CjtGAB9uEyCSqSWujICUXwghT57A5+ePEoMvUdc5a3XlSsgUhZGjGM/TGAqjz+SfuT7DDmGC6WzzeyOv0+2amOrr3KylzTUwjjDeWGbJJ9/COI
yvRFFv1iRsVGDaqYGWVsIoBZydsDhQGf/Z",
"$type" : "00"
}
}
3.2. findOne
findOne returns exactly one document that satisfies the specified query criteria.
String id = "5602de6e5d8bba0d6f2e45e4";
GridFSDBFile gridFsdbFile = gridFsTemplate.findOne(new Query(Criteria.where("_id").is(id)));
The code above will return the result record which was added in the example above. If the database contained more than one record which matched the query, it would return only one document. The specific record returned would be selected according to natural ordering (the order in which the documents were stored in the database).
3.3. find
find selects documents from a collection and returns a cursor to the selected documents.
Suppose we have the following database, containing 2 records:
[
{
"_id" : ObjectId("5602de6e5d8bba0d6f2e45e4"),
"metadata" : {
"user" : "alex"
},
"filename" : "test.png",
"aliases" : null,
"chunkSize" : NumberLong(261120),
"uploadDate" : ISODate("2015-09-23T17:16:30.781Z"),
"length" : NumberLong(855),
"contentType" : "image/png",
"md5" : "27c915db9aa031f1b27bb05021b695c6"
},
{
"_id" : ObjectId("5702deyu6d8bba0d6f2e45e4"),
"metadata" : {
"user" : "david"
},
"filename" : "test.png",
"aliases" : null,
"chunkSize" : NumberLong(261120),
"uploadDate" : ISODate("2015-09-23T17:16:30.781Z"),
"length" : NumberLong(855),
"contentType" : "image/png",
"md5" : "27c915db9aa031f1b27bb05021b695c6"
}
]
If we use the GridFsTemplate to execute the following query:
List<GridFSDBFile> gridFSDBFiles = gridFsTemplate.find(null);
The resulting list should contain two records, since we provided no criteria.
We can, of course, provide some criteria to the find method. For example, if we would like to get files whose metadata contains users with name alex, the code would be:
List<GridFSDBFile> gridFsdbFiles =
gridFsTemplate.find(new Query(Criteria.where("metadata.user").is("alex")));
The resulting list will contain only one record.
3.4. delete
delete removes documents from a collection.
Using the database from the previous example, suppose we have the code:
String id = "5702deyu6d8bba0d6f2e45e4";
gridFsTemplate.delete(new Query(Criteria.where("_id").is(id)));
After executing delete, only one record remains in the database:
{
"_id" : ObjectId("5702deyu6d8bba0d6f2e45e4"),
"metadata" : {
"user" : "alex"
},
"filename" : "test.png",
"aliases" : null,
"chunkSize" : NumberLong(261120),
"uploadDate" : ISODate("2015-09-23T17:16:30.781Z"),
"length" : NumberLong(855),
"contentType" : "image/png",
"md5" : "27c915db9aa031f1b27bb05021b695c6"
}
with chunks:
{
"_id" : ObjectId("5702deyu6d8bba0d6f2e45e4"),
"files_id" : ObjectId("5702deyu6d8bba0d6f2e45e4"),
"n" : 0,
"data" :
{
"$binary" : "/9j/4AAQSkZJRgABAQAAAQABAAD/4QAqRXhpZgAASUkqAAgAAAABADEBAgAHAAAAGgAAAAAAAABHb29nbGUAAP/bAIQAAwICAwICAwMDAwQDAwQFCAUFBAQFCgcHBggM
CgwMCwoLCw0OEhANDhEOCwsQFhARExQVFRUMDxcYFhQYEhQVFAEDBAQGBQUJBgYKDw4MDhQUFA8RDQwMEA0QDA8VDA0NDw0MDw4MDA0ODxAMDQ0MDAwODA8MDQ4NDA0NDAwNDAwQ/8AA
EQgAHAAcAwERAAIRAQMRAf/EABgAAQEBAQEAAAAAAAAAAAAAAAgGBwUE/8QALBAAAgEDAgQFAwUAAAAAAAAAAQIDBAURBiEABwgSIjFBYXEyUYETFEKhw
f/EABoBAAIDAQEAAAAAAAAAAAAAAAMEAQIFBgD/xAAiEQACAgEDBAMAAAAAAAAAAAAAAQIRAyIx8BJRYYETIUH/2gAMAwEAAhEDEQA/AHDyq1Bb6GjFPMAszLkZHHCTi1I6O
cXOFRZ1ZqoX6aqzRClkhb9MGVh2SsNyVI/hjG5389tuGcUaLK1GmFfpn5r3rnXpfV82pGtS3a0XmaGOO3zguKV1SWDwBQDH2uUWTOWMZzuM8bS0VQtJKRb2li9LL3l+4VNQPEfQTOB/WO
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fyZB+AeG80riueQdVfObC/tN1pLdaLfSxMiRQ08aIg2CjtGAB9uEyCSqSWujICUXwghT57A5+ePEoMvUdc5a3XlSsgUhZGjGM/TGAqjz+SfuT7DDmGC6WzzeyOv0+2amOrr3KylzTUwjjDeWGbJJ9/COI
yvRFFv1iRsVGDaqYGWVsIoBZydsDhQGf/Z",
"$type" : "00"
}
}
3.5. getResources
getResources returns all GridFsResource with the given file name pattern.
Suppose we have the following records in the database:
[
{
"_id" : ObjectId("5602de6e5d8bba0d6f2e45e4"),
"metadata" : {
"user" : "alex"
},
"filename" : "test.png",
"aliases" : null,
"chunkSize" : NumberLong(261120),
"uploadDate" : ISODate("2015-09-23T17:16:30.781Z"),
"length" : NumberLong(855),
"contentType" : "image/png",
"md5" : "27c915db9aa031f1b27bb05021b695c6"
},
{
"_id" : ObjectId("5505de6e5d8bba0d6f8e4574"),
"metadata" : {
"user" : "david"
},
"filename" : "test.png",
"aliases" : null,
"chunkSize" : NumberLong(261120),
"uploadDate" : ISODate("2015-09-23T17:16:30.781Z"),
"length" : NumberLong(855),
"contentType" : "image/png",
"md5" : "27c915db9aa031f1b27bb05021b695c6"
},
{
"_id" : ObjectId("5777de6e5d8bba0d6f8e4574"),
"metadata" : {
"user" : "eugen"
},
"filename" : "baeldung.png",
"aliases" : null,
"chunkSize" : NumberLong(261120),
"uploadDate" : ISODate("2015-09-23T17:16:30.781Z"),
"length" : NumberLong(855),
"contentType" : "image/png",
"md5" : "27c915db9aa031f1b27bb05021b695c6"
}
]
Now let’s execute getResources using a file pattern:
GridFsResource[] gridFsResource = gridFsTemplate.getResources("test*");
This will return the two records whose file names begin with “test” (in this case, they are both named test.png).
4. GridFSDBFile Core Methods
The GridFSDBFile API is quite simple as well:
- getInputStream – returns an InputStream from which data can be read
- getFilename – gets the filename of the file
- getMetaData – gets the metadata for the given file
- containsField – determines if the document contains a field with the given name
- get – gets a field from the object by name
- getId – gets the file’s object ID
- keySet – gets the object’s field names
5. Conclusion
In this article we looked at the GridFS features of MongoDB, and how to interact with them using Spring Data MongoDB.
The implementation of all these examples and code snippets can be found in my github project – this is an Eclipse based project, so it should be easy to import and run as it is.