Parsing a JSON to meet minimum requirements inside a stored procedure - json

Question

I have been looking at what I believe to every single page on SQL Server and half stackoverflow, and I can't find a proper solution to this
Our challenge, is to deal with an exiting application that send/receive JSON form SQL Server. So we have to build a STRONG JSON architecture on SQL Server.
We need to validate the format of the JSON (legacy system has its own standard) so messages are in exact expected format.
The thing is, JSON functions are not so advance as XML, and seems there is no way to validate a schema in SQL Server.
We tried with sp_prepare and sp_execute, but that does not seem to work.
We tested something like this:
Declare #ptSQL1 int;
Exec sp_prepare #ptSQL1 output,
N'#P1 nvarchar(128), #json NVARCHAR(1000) ',
N' SELECT *
INTO temp_tblPersons
FROM OPENJSON (#json, ''$.root'')
WITH (
Cname NVARCHAR(100) ''strict$.FirstName'',
Csurname NVARCHAR(100) ''lax$.surname''
) as J
where Csurname like #P1';
DECLARE #json7 NVARCHAR(1000)
SET #json7 = N'{
"root": [
{ "FirstName": "Charles" , "surname":"perez" },
{ "FirstName": "Jade" , "surname":"pelaz" },
{ "FirstName": "Jim" , "surname":"alvarez" },
{ "FirstName": "Luke" , "surname":"alonso" },
{ "FirstName": "Ken"}
]
}'
IF (#ptSQL1 = 0) PRINT 'THE SUPPLY JSON IS NOT VALID'
ELSE Exec sp_execute #ptSQL1, N'a%', #json7;
but does not meet the sp_prepare/execute behavior.
Our intention it to validate a minimum schema before proceed to process the data, and if the schema doesn't meet the standard, return an ERROR.
How can this be accomplished?
(not sure where we read the #ptSQL1 = 0, but I believe to read somewhere)

Answer 1

Our intention it to validate a minimum schema before proceed to
process the data, and if the schema doesn't meet the standard, return
an ERROR.
The JSON must be parsed in order to validate the schema. A prepare doesn't actually execute the query in order to parse the JSON document, plus sp_prepare and sp_execute are internal API system stored procedures not intended to be called directly in T-SQL.
Although one can't currently validate JSON schema in T-SQL (without writing a custom SQLCLR assembly), you could just use TRY/CATCH and handle errors. The example below handles JSON errors differently but I would personally just THROW all errors and handle specific ones in the app code.
DECLARE #json NVARCHAR(1000);
DECLARE #P1 NVARCHAR(128) = 'a%';
SET #json = N'{
"root": [
{ "FirstName": "Charles" , "surname":"perez" },
{ "FirstName": "Jade" , "surname":"pelaz" },
{ "FirstName": "Jim" , "surname":"alvarez" },
{ "FirstName": "Luke" , "surname":"alonso" },
{ "FirstName": "Ken"}
]
}';
BEGIN TRY
SELECT *
INTO temp_tblPersons
FROM OPENJSON (#json, '$.root')
WITH (
Cname NVARCHAR(100) 'strict$.FirstName',
Csurname NVARCHAR(100) 'lax$.surname'
) as J
where Csurname like #P1;
END TRY
BEGIN CATCH
DROP TABLE IF EXISTS temp_tblPersons;
IF ERROR_MESSAGE() LIKE N'%JSON%'
BEGIN
PRINT 'THE SUPPLY JSON IS NOT VALID';
END
ELSE
BEGIN
THROW;
END;
END CATCH;