1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259
|
+++
date = "2016-06-12T17:29:57-04:00"
title = "GridFS"
[menu.main]
parent = "Sync Tutorials"
identifier = "GridFS"
weight = 90
pre = "<i class='fa'></i>"
+++
## GridFS
[GridFS]({{< docsref "core/gridfs">}}) is a specification for storing and retrieving files that exceed the BSON document size limit of 16MB. Instead of storing a file in a single document, GridFS divides a file into parts, or chunks, and stores each of those chunks as a separate document.
When you query a GridFS store for a file, the Java driver will reassemble the chunks as needed.
The following code snippets come from the [`GridFSTour.java`]({{< srcref "driver/src/examples/gridfs/GridFSTour.java">}}) example code
that can be found with the driver source on github.
## Prerequisites
Include the following import statements:
```java
import com.mongodb.Block;
import com.mongodb.MongoClient;
import com.mongodb.client.MongoDatabase;
import com.mongodb.client.gridfs.*;
import com.mongodb.client.gridfs.model.*;
import org.bson.Document;
import org.bson.types.ObjectId;
import java.io.*;
import java.nio.file.Files;
import java.nio.charset.StandardCharsets;
import static com.mongodb.client.model.Filters.eq;
```
## Connect to a MongoDB Deployment
Connect to a MongoDB deployment and declare and define a `MongoDatabase` instance.
For example, include the following code to connect to a standalone MongoDB deployment running on localhost on port `27017`:
```java
MongoClient mongoClient = new MongoClient();
```
For additional information on connecting to MongoDB, see [Connect to MongoDB]({{< ref "connect-to-mongodb.md">}}).
## Create a GridFS Bucket
GridFS stores files in [two collections]({{<docsref "core/gridfs/#gridfs-collections">}}): a `chunks` collection stores the file chunks, and a `files` collection stores file metadata. The two collections are in a common bucket and the collection names are prefixed with the bucket name.
The Java driver provides the [`GridFSBuckets.create()`]({{< apiref "com/mongodb/client/gridfs/GridFSBuckets.html#create-com.mongodb.client.MongoDatabase-" >}}) method
to create the [`GridFSBucket`]({{< apiref "com/mongodb/client/gridfs/GridFSBucket" >}}).
```java
MongoDatabase myDatabase = mongoClient.getDatabase("mydb");
// Create a gridFSBucket using the default bucket name "fs"
GridFSBucket gridFSBucket = GridFSBuckets.create(myDatabase);
```
You can specify a bucket name to [`GridFSBuckets.create()`]({{< apiref "com/mongodb/client/gridfs/GridFSBuckets.html#create-com.mongodb.client.MongoDatabase-java.lang.String-">}}) method.
```java
// Create a gridFSBucket with a custom bucket name "files"
GridFSBucket gridFSFilesBucket = GridFSBuckets.create(myDatabase, "files");
```
{{% note %}}
GridFS will automatically create indexes on the `files` and `chunks` collections on first upload of data into the GridFS bucket.
{{% /note %}}
## Upload to GridFS
To upload data into GridFS, you can upload from an `InputStream` or write data to a `GridFSUploadStream`.
### UploadFromStream
The [`GridFSBucket.uploadFromStream`]({{< apiref "com/mongodb/client/gridfs/GridFSBucket.html#openUploadStream-java.lang.String-com.mongodb.client.gridfs.model.GridFSUploadOptions-" >}}) method reads the contents of an [`InputStream`](http://docs.oracle.com/javase/8/docs/api/index.html?java/io/InputStream.html) and saves it to the `GridFSBucket`.
You can use the [`GridFSUploadOptions`]({{< apiref "com/mongodb/client/gridfs/model/GridFSUploadOptions" >}}) to configure the chunk size or include additional metadata.
The following example uploads an `InputStream` into `GridFSBucket`:
```java
// Get the input stream
try {
InputStream streamToUploadFrom = new FileInputStream(new File("/tmp/mongodb-tutorial.pdf"));
// Create some custom options
GridFSUploadOptions options = new GridFSUploadOptions()
.chunkSizeBytes(358400)
.metadata(new Document("type", "presentation"));
ObjectId fileId = gridFSBucket.uploadFromStream("mongodb-tutorial", streamToUploadFrom, options);
} catch (FileNotFoundException e){
// handle exception
}
```
### OpenUploadStream
You can write data to a [`GridFSUploadStream`]({{< apiref "mongodb/client/gridfs/GridFSUploadStream.html">}}) which extends [`OutputStream`](http://docs.oracle.com/javase/8/docs/api/index.html?java/io/OutputStream.html). The [`GridFSBucket.openUploadStream`]({{< apiref "com/mongodb/client/gridfs/GridFSBucket.html#openUploadStream-java.lang.String-com.mongodb.client.gridfs.model.GridFSUploadOptions-">}}) method returns a [`GridFSUploadStream`]({{< apiref "mongodb/client/gridfs/GridFSUploadStream.html">}}).
The `GridFSUploadStream` buffers data until it reaches the `chunkSizeBytes` and then inserts the chunk into the `chunks` collection. When the `GridFSUploadStream` is closed, the final chunk is written and the file metadata is inserted into the `files` collection.
The following example uploads into a `GridFSBucket` via the returned `GridFSUploadStream`:
```java
try {
GridFSUploadOptions options = new GridFSUploadOptions()
.chunkSizeBytes(358400)
.metadata(new Document("type", "presentation"));
GridFSUploadStream uploadStream = gridFSFilesBucket.openUploadStream("mongodb-tutorial-2", options);
byte[] data = Files.readAllBytes(new File("/tmp/MongoDB-manual-master.pdf").toPath());
uploadStream.write(data);
uploadStream.close();
System.out.println("The fileId of the uploaded file is: " + uploadStream.getObjectId().toHexString());
} catch(IOException e){
// handle exception
}
```
## Find Files Stored in GridFS
To find the files stored in the `GridFSBucket` use the [`find`]({{< apiref "com/mongodb/client/gridfs/GridFSBucket.html#find--">}}) method.
The following example prints out the filename of each file stored:
```java
gridFSBucket.find().forEach(
new Block<GridFSFile>() {
public void apply(final GridFSFile gridFSFile) {
System.out.println(gridFSFile.getFilename());
}
});
```
You can also provide a custom filter to limit the results returned. The following example prints out the filenames of all files with a "image/png" value set as the contentType in the user defined metadata document:
```java
gridFSBucket.find(eq("metadata.contentType", "image/png")).forEach(
new Block<GridFSFile>() {
public void apply(final GridFSFile gridFSFile) {
System.out.println(gridFSFile.getFilename());
}
});
```
## Download from GridFS
There are various ways to download data from GridFS.
### DownloadToStream
The [`downloadToStream`]({{< apiref "com/mongodb/client/gridfs/GridFSBucket.html#downloadToStream-org.bson.types.ObjectId-java.io.OutputStream-" >}}) method reads the contents from MongoDB and writes the data directly to the provided [`OutputStream`](http://docs.oracle.com/javase/8/docs/api/index.html?java/io/OutputStream.html).
To download a file by its file `_id`, pass the `_id` to the method. The
following example downloads a file by its file `_id` into the provided
`OutputStream`:
```java
ObjectId fileId; //The id of a file uploaded to GridFS, initialize to valid file id
try {
FileOutputStream streamToDownloadTo = new FileOutputStream("/tmp/mongodb-tutorial.pdf");
gridFSBucket.downloadToStream(fileId, streamToDownloadTo);
streamToDownloadTo.close();
System.out.println(streamToDownloadTo.toString());
} catch (IOException e) {
// handle exception
}
```
If you don't know the `_id` of the file but know the filename, then you can pass the filename to the [`downloadToStream`]({{< apiref "com/mongodb/client/gridfs/GridFSBucket.html#downloadToStream-java.lang.String-java.io.OutputStream-com.mongodb.client.gridfs.model.GridFSDownloadOptions-" >}}) method. By default, it will download the latest version of the file. Use the [`GridFSDownloadOptions`]({{< apiref "com/mongodb/client/gridfs/model/GridFSDownloadOptions.html" >}}) to configure which version to download.
The following example downloads the original version of the file named "mongodb-tutorial" into the `OutputStream`:
```java
try {
FileOutputStream streamToDownloadTo = new FileOutputStream("/tmp/mongodb-tutorial.pdf");
GridFSDownloadOptions downloadOptions = new GridFSDownloadOptions().revision(0);
gridFSBucket.downloadToStream("mongodb-tutorial", streamToDownloadTo, downloadOptions);
streamToDownloadTo.close();
} catch (IOException e) {
// handle exception
}
```
### OpenDownloadStream
The [`openDownloadStream`]({{< apiref "com/mongodb/client/gridfs/GridFSBucket.html#openDownloadStream-org.bson.types.ObjectId-">}}) method returns a [`GridFSDownloadStream`]({{< apiref "com/mongodb/client/gridfs/GridFSDownloadStream.html">}}) which extends [`InputStream`](http://docs.oracle.com/javase/8/docs/api/index.html?java/io/InputStream.html).
The following example reads from the `GridFSBucket` via the returned `InputStream`:
```java
ObjectId fileId; //The id of a file uploaded to GridFS, initialize to valid file id
GridFSDownloadStream downloadStream = gridFSBucket.openDownloadStream(fileId);
int fileLength = (int) downloadStream.getGridFSFile().getLength();
byte[] bytesToWriteTo = new byte[fileLength];
downloadStream.read(bytesToWriteTo);
downloadStream.close();
System.out.println(new String(bytesToWriteTo, StandardCharsets.UTF_8));
```
You can also pass the filename to the [`openDownloadStream`]({{< apiref "com/mongodb/client/gridfs/GridFSBucket.html#openDownloadStream-java.lang.String-com.mongodb.client.gridfs.model.GridFSDownloadOptions-" >}}) method. By default it will download the latest version of the file. Use the [`GridFSDownloadOptions`]({{< apiref "com/mongodb/client/gridfs/model/GridFSDownloadOptions.html" >}}) to configure which version to download.
The following example downloads the latest version of the file named "sampleData" into the `OutputStream`:
```java
GridFSDownloadStream downloadStream = gridFSBucket.openDownloadStream("sampleData");
int fileLength = (int) downloadStream.getGridFSFile().getLength();
byte[] bytesToWriteTo = new byte[fileLength];
downloadStream.read(bytesToWriteTo);
downloadStream.close();
System.out.println(new String(bytesToWriteTo, StandardCharsets.UTF_8));
```
## Rename files
If you should need to rename a file, then use the [`rename`]({{< apiref "com/mongodb/client/gridfs/GridFSBucket.html#rename-org.bson.types.ObjectId-java.lang.String-">}}) method.
The following example renames a file to "mongodbTutorial":
```java
ObjectId fileId; //ObjectId of a file uploaded to GridFS
gridFSBucket.rename(fileId, "mongodbTutorial");
```
{{% note %}}
The `rename` method requires an `ObjectId` rather than a `filename` to ensure the correct file is renamed.
To rename multiple revisions of the same filename, first retrieve the full list of files. Then for every file that should be renamed then execute `rename` with the corresponding `_id`.
{{% /note %}}
## Delete files
To delete a file from the `GridFSBucket` use the [`delete`]({{< apiref "com/mongodb/client/gridfs/GridFSBucket.html#delete-org.bson.types.ObjectId-">}}) method.
The following example deletes a file from the `GridFSBucket`:
```java
ObjectId fileId; //ObjectId of a file uploaded to GridFS
gridFSBucket.delete(fileId);
```
|