Mapper 2.0: Iterate over an array

Tom Santiago

Updated May 29, 2024 15:09

When your source JSON data contains an array of items that you want to independently map, use the bracketed wildcard syntax [*] on the parent object, then use dot notation to select each object in the array. For example, consider the following source data:

{
  "orderId": 123,
  "total": 99.99,
  "state": "ca",
  "items": [
    {
      "description": "Hat",
      "qty": 3
    },
    {
      "description": "Shoes",
      "qty": 1
    }
  ]
}

In the above JSON, the items array contains multiple objects, each of which has a description field and a qty field. Also notice that the orderId field is not included in the items array.

For this example, the destination application requires the following format:

{
  "items": [
    {
      "description": "Hat",
      "quantity": 3,
      "orderID": 123
    },
    {
      "description": "Shoes",
      "quantity": 1,
      "orderID": 123
    }
  ]
}

Use the following steps to generate the above destination JSON structure from the source data using Mapper 2.0.

Destination (left column)	Source (right column)
Create the items object array in the left column (destination). Name the destination object array items . Set the data type to [object].	In the right column (source), use JSONPath notation to reference the items object array from the source data: `$.items[*]`.
Add the description string field to the left column (destination).	Select the description field from the right column (source): `@.items.description`.
Add the quantity number field to the destination.	Select the qty field from the source data: `@.items.qty`.
Add the orderID number field to the destination object.	Select the orderId from the source data: `$.orderId`.

Tip

Tips: In this example, notice the following:

Specify the wildcard [*] to select all fields returned within the parent object array ( items). Never use wildcard syntax to select the child fields contained within an array of objects. Instead, use dot notation to select each child field.
You can add fields from any part of the source data as nested fields in a destination JSON object array. The above example adds orderId to the objects included in the destination items array.