ZappySys - SSIS, import JSON where JSON elements are missing sometimes - json

Question

Using ZappySys in SSIS to import JSON data from a 3rd party.
All working well, but sometimes the 3rd party doesn't include the same elements each time. Samples below:
The first works as it includes the expected Equipment and Catering cost elements that I have supplied in the Sample JSON string section of the "ZS JSON Parser Transform" screen
{
"RoomCost": {
"Net": 150,
"Tax": 0,
"Gross": 150
},
"CateringCost": {
"Net": 187.2,
"Tax": 0,
"Gross": 187.2
},
"EquipmentCost": {
"Net": 0,
"Tax": 0,
"Gross": 0
},
"Discount": {
"Net": 0,
"Tax": 0,
"Gross": 0
},
"Total": {
"Net": 337.2,
"Tax": 0,
"Gross": 337.2
}
}
The example below fails to import with NULL errors in the logs as the Equipment and Catering elements are not supplied. Error is
{
"RoomCost": {
"Net": 150,
"Tax": 0,
"Gross": 150
},
"Discount": {
"Net": 0,
"Tax": 0,
"Gross": 0
},
"Total": {
"Net": 337.2,
"Tax": 0,
"Gross": 337.2
}
}
Error: The type of the value (DBNull) being assigned to variable "User::mCateringCostGross" differs from the current variable type (Decimal). Variables may not change type during execution. Variable types are strict, except for variables of type Object.
What is the best way to handle this situation?

Answer 1

The fix for this was to include a Derived Column task between the ZappySys JSON source and the output, to convert nulls to default values.