translate bson -> json on the fly

[Jordan Orelli]

is it possible to translate bson into json on the fly?  I inherited a database that isn't modelled the way that I would model it, but there's also a client that already uses the json representation of these documents.  I'm going to change their structure, but as a stop-gap I want to simply expose some bson documents as json, since that's basically all the existing system was doing (without processing the data).  Anybody have any idea how I could translate a bson doc into json without knowing its structure in advance?

[Jordan Orelli]

err, I guess I should clarify:  I want to take the result of a query and turn it into json.  Iter.Next is internally unmarhasling the data, but I don't actually need to unmarshal the returned documents into a struct; I just want to print the result to json.

[Gustavo Niemeyer]

Hey Jordan,

On Fri, Apr 6, 2012 at 16:15, Jordan Orelli <jordan...@gmail.com> wrote:
> err, I guess I should clarify:  I want to take the result of a query and
> turn it into json.  Iter.Next is internally unmarhasling the data, but I
> don't actually need to unmarshal the returned documents into a struct; I
> just want to print the result to json.

Yeah, that's doable, and simple. Just using a map to load the document
from your query result, and then marshal the same map to json.

var m bson.M
err := query.One(&m)
... marshal m onto json ....

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Gustavo Niemeyer
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-- I'm not absolutely sure of anything.

[Erik Unger]

I would be quite convenient to have that functionality in mgo/bson (also more efficient if implemented directly).

Since JSON is the natural text representation of BSON, what about allowing *string as destination for BSON unmarshalling?

bson.Raw.String() would also look quite natural and be handy for debugging.

-Erik

[Gustavo Niemeyer]

Hi Erik,

On Sun, Jul 29, 2012 at 6:23 AM, Erik Unger <ung...@gmail.com> wrote:
> I would be quite convenient to have that functionality in mgo/bson (also
> more efficient if implemented directly).

As I explained, converting to a map and then to json is trivial to do
with normal code, if that's what you're interested in doing.

> Since JSON is the natural text representation of BSON, what about allowing
> *string as destination for BSON unmarshalling?

It is actually not a proper text representation for BSON. MongoDB uses
several custom types to be able to represent the spectrum of BSON
typing in Javascript.

> bson.Raw.String() would also look quite natural and be handy for debugging.

If you want to see its content, just unmarshal it in a map and print the map:

func debugRaw(raw bson.Raw) {
var m map[string]interface{}
if err := raw.Unmarshal(&m); err != nil {
panic(err)
}
fmt.Printf("%#v\n", m)
}

>
> -Erik



--

gustavo @ http://niemeyer.net