download a file from mongodb database

[Bralima Branding]

Hey,
can someone help me. I am using a mongodb database and gridfs. I can
upload files to my database, but I don't know how to download those
files.

I'm just starting with mongodb, and I am using coffeescript.

Thanks for your help

[Eliot Horowitz]

This really depends on your setup.
When you say coffeescript, do you mean server side or client side?
If server side, what server?

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[Saar Korren]

You need some script which can serve static files from the database.
The simplest set-up is to have a script which takes a filename as
input, and retrieves the file's contents, flushing those to the
output. It is recommended to use a driver which allows reading the
file as a stream to save on memory. For instance, the Java driver can
return the file's content as an InputStream, while the PHP driver can
only return the entire file as a single memory chunk.

The issue with the above method is that it skips important static file
specification details used for caching, such as ETag and If-Modified
headers. These are not strictly required for the site to work, but it
would cause a lot of load to skip those, as it would cause the browser
not to cache any of the served files.

Unfortunately, most server frameworks do not have a ready-made static
file service which merely requires plugging the file data in. Chances
are you will have to follow the specifications and write a lot of the
related code yourself. There is a very good static files servlet
example for Java here:
http://balusc.blogspot.com/2009/02/fileservlet-supporting-resume-and.html

You may be able to adapt that code to work with your own language and
server. Provided you can read Java, at least.

[Bralima Branding]

Hi,

Thanks for your contributions.
Eliot, I am using coffescript in the server with nodejs in a linux server.I have a mongodb Database, I ear about one tool called  nginx-gridfs, but I still can not find tutorials on how to use it.

Saar, I checked the link that you provide, but I didn't get this java code...

[Eliot Horowitz]

There are a number of options for serving files from node.js.

http://mongodb.github.com/node-mongodb-native/markdown-docs/gridfs.html

https://github.com/jamescarr/nodejs-mongodb-streaming

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[Bralima Branding]

Thank you very elliot, i used your second link and i can download file
now, mixing mongodb gridfs and node js fs modules.
But, So far, I can only download .txt files, I have a big problem with
others extensions like .docx, .pdf, ijpg etc..

Here is an example of downloading from my code, thank for your help

var fs = require("fs")
var Mongolian = require("mongolian")
var server = new Mongolian
var db = server.db("test")
var files = db.collection("fs.files")
var mime = require("mime")

var gridfs = db.gridfs()

// Create new file write stream
var stream = gridfs.findOne('test.jpg', function(err, file) {
if (err) throw err
var stream = file.readStream()
var content = ''
stream.on('data',function(chunk) { content +=
chunk.toString() })
stream.on('error', function(error) {
console.log(error)
})
stream.on('end',function() {
// console.log(content)
fs.writeFile('fs/test.jpg', content, function (err) {
if (err) throw err;
console.log('It\'s saved!');
});

});

});

In this code i trie to download the file test.jpg from my mongodb
database to my fs folder... the file is created, but it's empty. I
think it's a encoding problem or something.. how to solve it ??? It's
the same with pdf, docx, odt files etc...


Thanks

[Christian Kvalheim]

don't use mongolian. have a look at the example

http://mongodb.github.com/node-mongodb-native/api-generated/gridstore.html#read

should be fairly easy to understand

also have a look at the docs in general

http://mongodb.github.com/node-mongodb-native

Best of luck

Cheers

[Bralima Branding]

Thank you very much christiam, it's working correctly now..

cheers

On May 15, 8:19 pm, Christian Kvalheim <chris...@gmail.com> wrote:
> don't use mongolian. have a look at the example
>

> http://mongodb.github.com/node-mongodb-native/api-generated/gridstore...