Is there a way to do deep copy using apache VTL?
I was trying to use x-amazon-apigateway-integration using requestTemplates.
The input JSON is as shown below,
{
"userid": "21d6523137f6",
"time": "2020-06-16T15:22:33Z",
"item": {
"UserID" : { "S": "21d6523137f6" },
<... some complex json nodes here ...>,
"TimeUTC" : { "S": "2020-06-16T15:22:33Z" },
}
}
The requestTemplate is as shown below,
requestTemplates:
application/json: !Sub
- |
#set($inputRoot = $input.path('$'))
{
"TableName": "${tableName}",
"ConditionExpression": "attribute_not_exists(TimeUTC) OR TimeUTC > :sk",
"ExpressionAttributeValues": {
":sk":{
"S": "$util.escapeJavaScript($input.path('$.time'))"
}
},
"Item": "$input.path('$.item')", <== Copy the entire item over to Item.
"ReturnValues": "ALL_OLD",
"ReturnConsumedCapacity": "INDEXES",
"ReturnItemCollectionMetrics": "SIZE"
}
- {
tableName: !Ref EventsTable
}
The problem is, the item gets copied like,
"Item": "{UserID={S=21d6523137f6}, Lat={S=37.33180957}, Lng={S=-122.03053391}, ... other json elements..., TimeUTC={S=2020-06-16T15:22:33Z}}",
As you can see, the whole nested json become a single atribute. While I expected it to become a fully blown json node on its own like below,
"Item": {
"UserID" : { "S": "21d6523137f6" },
"Lat": { "S": "37.33180957" },
"Lng": { "S": "-122.03053391" },
<.... JSON nodes ...>
"TimeUTC" : { "S": "2020-06-20T15:22:33Z" }
},
Is it possible to deep/nested copy operation on a json node like above without doing the kung-fu of iterating the node and appending the childs o a json node variable etc...
btw, I'm using AWS API Gateway request template, so it may not support all the Apache VTL templating options.
You need to use the $input.json method instead of $input.path.
"Item": $input.json('$.item'),
Note that I removed the double quotes.
If you had the double quotes because you want to stringify $.item, you can do that like so:
"Item": "$util.escapeJavaScript($input.json('$.item'))",