Ballerina json datetime value - json

Question

i have to index documents to elasticsearch to an index which has a date field mapping and i'm trying to build a json with this date value, but ballerina says this seems not possible.
I thought about storing this date value into an xml and after that to convert it to a json but xml has the same problem (i thought this might be a trick...).
I tried to store it into a string and after that to extract the json payload from that string but it gives me this error:
error: {ballerina/io}GenericError message=unrecognized token 'date=time=1591128342000'
I thought about dealing with this string to date conversion from inside elasticsearch but i would like to keep this scenario as the last one. I don't like it, beacause i have to do some queries based on timestamp after and storing date as a string would give me additional problems
So is there any way to trick ballerina in order to achive this json containing a date value ?
-----here is snapshot of the code giving me the error-----
It says:
incompatible types: expected 'json', found 'ballerina/time:Time'

Answer 1

JSON is a text format that is completely language independent (see e.g. json.org).
time:Time is a Ballerina language specific type JSON knows nothing about. Because there is no implicit conversion (for a good reason) one have to provide the conversion.
In this case you most likely want to convert time:Time to a ISO 8601 string presentation with time:toString.
The following code (Ballerina 1.2):
import ballerina/io;
import ballerina/time;
public function main() {
var btime = time:currentTime();
var j = <json> {
time: time:toString(btime)
};
io:println(j.toJsonString());
}
Correctly prints:
{"time":"2020-06-03T08:39:07.897+03:00"}
Maryam Ziyad has written a good introduction to Ballerina's JSON support.

Answer 2

The following code is updated for Ballerina Swan Lake Update 1 (2201.1.0) to show how to convert a Ballerina UTC time (time:Utc) to JSON representation. Note that it's also possible to use localized time (time:Civil) but that is no different from time to JSON conversion point of view.
One can read more about Ballerina time handling from the documentation of time module.
import ballerina/io;
import ballerina/time;
public function main() {
time:Utc now = time:utcNow(3);
json j = {
time: time:utcToString(now)
};
io:println(j.toJsonString());
}
That correctly prints:
{"time":"2022-07-20T06:03:46.078Z"}