Using Mongo and GridFS to store images

August 26, 2012

GridFS is Mongo specification to store files, claims to be better than file system but to me querying files it’s what makes it lots better and it’s very straight forward.

I am using a POJO to use within the service that performs the operations

public class MongoStoredFile {

    private String id;
    private File file;
    private String name;
    private String contentType;
    private byte[] data;
    private InputStream inputStream;
}

The service receives a MongoStoredFile object and saves it

public String save(MongoStoredFile file) throws IOException {
    GridFS gridFS = new GridFS(mongoTemplate.getDb(),"images");
    GridFSInputFile inputFile = gridFS.createFile(file.getData());
    inputFile.setContentType(file.getContentType());
    inputFile.setFilename(file.getName());
    inputFile.save();
    return inputFile.getId().toString();
}

it’s very straight forward

create a GridFS object, receives two arguments a connection and a collections name, in this case “images”
create a GridFSInputFile with files binary data
set the content type
set a name
save it

that simple

Now if you want to retrieve the stored object, here the id is being passed as argument, but you can create a query and handle the results.

public MongoStoredFile getFile(String objectId) throws IOException  {
    GridFS gridFS = new GridFS(mongoTemplate.getDb(),"images");
    GridFSDBFile file = gridFS.find(new ObjectId(objectId));

    ...
}

you pass a mongo connection and a collection’s name
execute a query with gridFS.find and you obtain a reference to a GridFSDBFile object

Now you need to extract the values and put them in our POJO MongoStoredFile

public MongoStoredFile getFile(String objectId) throws IOException  {
    GridFS gridFS = new GridFS(mongoTemplate.getDb(),"images");
    GridFSDBFile file = gridFS.find(new ObjectId(objectId));

    ...

    MongoStoredFile mongoStoredFile = new MongoStoredFile();
    mongoStoredFile.setId(objectId.toString());
    mongoStoredFile.setName((String) file.get("filename"));
    mongoStoredFile.setContentType((String) file.get("contentType"));
    mongoStoredFile.setInputStream(file.getInputStream());
    return mongoStoredFile;
}

that’s our service

From the client side we only need to call our service, there’s some plumbing to it though

JSP looks like:

<form:form action="${imagesUpload}" enctype="multipart/form-data" id="imageForm" commandName="mongoStoredFile" name="imageForm" method="POST">
    <fieldset>
        <p>
            <label for="subject">File:</label>
            <form:input path="file" type="file" id="file" 
                        placeholder="File:" required="required" />
        </p>
        <p>
            <input type="submit" id="formButton" value="Upload File" >
        </p>
    </fieldset>
</form:form>

and the server counterpart

public void upload(@RequestParam("file") MultipartFile multipartFile, final HttpServletResponse response) throws IOException {
    if (multipartFile == null) {
        throw new RuntimeException("file null");
    }
    MongoStoredFile image = new MongoStoredFile();
    image.setName(multipartFile.getOriginalFilename());
    image.setContentType(multipartFile.getContentType());
    image.setData(multipartFile.getBytes());
    fileService.save(image);
}

The post would not be complete without an example of a file hosted in this casa. I have taken keen interest in this JVM language for the last month. I am seriously contemplating moving my efforts into that direction.

Scala *

You can see the rest of the code at: https://github.com/lnramirez/lnramirez

*Image taken from: http://www.scala-lang.org/docu/files/packageobjects/scala-logo.png

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