Unmarshall json into database json field for postgres

Question

type A struct {
   Id int64
   ContactInfo sql.NullString `sql:"type:json"`
}

Given this json - {"Id": 1, "ContactInfo": {"email1": "[email protected]", "phone1": "2223334444"}}, how do we go about Unmarshaling the json into struct A. ContactInfo is just a simple json data type in postgres. I've looked around, but can't seem to find any easy way. Without any special handling, I simply get an error if I json.Unmarshal (error reads - json: cannot unmarshal object into Go value of type string).

What is desired is to leave ContactInfo untouched as a string so we can send it into postgres directly and postgres will verify if its valid json. However, Id should be unmarshaled and assigned as struct value.

Michael Banzon · Accepted Answer · 2014-05-21 20:31:31Z

7

To parse JSON with embedded JSON you need to use a field of type json.RawMessage (and a second struct).

Check out this example for basic usage. You will then have access to the raw field contents for use in your database related structure.

edited May 21, 2014 at 20:31

answered May 21, 2014 at 20:16

Michael Banzon

4,9651 gold badge29 silver badges28 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

sat Over a year ago

Thanks. Then how do we convert from json.RawMessage back into a string? I looked at the methods available for RawMessage. Can't find anything that gives me back a string. Postgres json is nothing but a text data type with some additional semantics attached. So the contactinfo should become a string in the end.

Michael Banzon Over a year ago

You just cast the json.RawMessage to a string. See the updated Playground link in the answer.

sat Over a year ago

Oh! Interesting. I didn't know one could simply cast it like in other languages. Long way to go (pun intended) still to fully understand go

sat Over a year ago

For those still in the learn mode like me - the type conversion is actually written in the spec. See this - golang.org/ref/spec#Conversions

Michael Banzon Over a year ago

Yes. My initial comment stated that json.RawMessage should be cast to a string when it is in fact a type conversion ant not a cast.

Collectives™ on Stack Overflow

Unmarshall json into database json field for postgres

1 Answer 1

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related