Mule ESB dataweave how to ignore null - mule

Question

In mule ESB dataweave I am having trouble ignoring empty objects, {}.
I am trying to check if a particular table exists in my input. If it exists, I do some business logic, if it doesn't exist, it should not be included in the output. However, I am getting {} instead of nothing.
This is my input file :
{
"srcTable": {
"srcList": [
{
"tableNames": "table1",
"src": [
{
"srcKey": [
{
"key": "date",
"value": "01/01/2016"
},
{
"key": "withinYearTotalMaxSection",
"value": "2500"
},
{
"key": "previousClaimsTotalMaxSection",
"value": "25000"
},
{
"key": "previousClaimsTotalMax",
"value": "50000"
}
]
}
]
},
{
"tableNames": "table2",
"src": [
{
"srcKey": [
{
"key": "date",
"value": "01/01/2016"
},
{
"key": "type",
"value": "A"
},
{
"key": "garden",
"value": "1000"
},
{
"key": "risk",
"value": "50000"
}
]
},
{
"srcKey": [
{
"key": "date",
"value": "01/01/2016"
},
{
"key": "type",
"value": "B"
},
{
"key": "garden",
"value": "0"
},
{
"key": "risk",
"value": "50000"
}
]
}
]
},
{
"tableNames": "table3",
"src": [
{
"srcKey": [
{
"key": "date",
"value": "01/01/2016"
},
{
"key": "type",
"value": "GLD"
},
{
"key": "plants",
"value": "1500"
},
{
"key": "theft",
"value": "3000"
}
]
},
{
"srcKey": [
{
"key": "date",
"value": "01/01/2016"
},
{
"key": "type",
"value": "SVR"
},
{
"key": "plants",
"value": "0"
},
{
"key": "theft",
"value": "1000"
}
]
}
]
}
]
}
}
This is my dataweave:
%dw 1.0
%output application/json skipNullOn="everything"
---
{
singlevalue: [
{
(payload.srcTable.srcList filter ($.tableNames == 'table1') map (r,pos)-> {
(r.src map {
($.srcKey filter ($.key == 'date') map {
name: 'date',
value: $.value
})
})
})
},
{
(payload.srcTable.srcList filter ($.tableNames != null and $.tableNames == 'xxx') map (r,pos)-> {
(r.src map {
($.srcKey filter ($.key == 'date') map {
name: 'date' when $.value != null otherwise null,
value: $.value
})
})
})
}
]
}
This output file :
{
"singlevalue": [
{
"name": "date",
"value": "01/01/2016"
},
{}
]
}
Can anyone suggest how to get rid of the empty objects, {}, please?
Thank you and regards
NK

Answer 1

The easiest thing to do would be to remove all the empty elements at the end like this:
%dw 1.0
%output application/json skipNullOn="everything"
%var transformation = [
{
(payload.srcTable.srcList filter ($.tableNames == 'table1') map (r,pos)-> {
(r.src map {
($.srcKey filter ($.key == 'date') map {
name: 'date',
value: $.value
})
})
})
},
{
(payload.srcTable.srcList filter ($.tableNames != null and $.tableNames == 'xxx') map (r,pos)-> {
(r.src map {
($.srcKey filter ($.key == 'date') map {
name: 'date' when $.value != null otherwise null,
value: $.value
})
})
})
}
]
%function removeEmptyObjects(e)
e filter $ != {}
---
{ singleValue: removeEmptyObjects(transformation) }
This outputs:
{
"singleValue": [
{
"name": "date",
"value": "01/01/2016"
}
]
}

Answer 2

With Josh's help this is the solution if anyone interested.
Using the size Of with the filter combination
%dw 1.0
%output application/json skipNullOn="everything"
{
singlevalue: [
({
(payload.srcTable.srcList filter ($.tableNames == 'table1') map (r,pos)-> {
(r.src map {
($.srcKey filter ($.key == 'date') map {
name: 'date',
value: $.value
})
})
})
}) when (sizeOf (payload.srcTable.srcList filter $.tableNames == 'table1')) != 0,
({
(payload.srcTable.srcList filter ($.tableNames != null and $.tableNames == 'xxx') map (r,pos)-> {
(r.src map {
($.srcKey filter ($.key == 'date') map {
name: 'date' when $.value != null otherwise null,
value: $.value
})
})
})
}) when (sizeOf (payload.srcTable.srcList filter $.tableNames == 'xxx')) != 0]}