ItemsPath (Map, JSONPath only) - AWS Step Functions (original) (raw)

In JSONPath-based states, use the ItemsPath field to select an array within a JSON input provided to a Map state. TheMap state repeats a set of steps for each item in the array. By default, the Map state sets ItemsPath to $, which selects the entire input. If the input to the Map state is a JSON array, it runs an iteration for each item in the array, passing that item to the iteration as input.

Note

You can use ItemsPath in the Distributed Map state only if you use a JSON input passed from a previous state in the workflow.

You can use theItemsPath field to specify a location in the input that points to JSON array used for iterations. The value of ItemsPath must be a Reference Path, and that path must point to JSON array. For instance, consider input to aMap state that includes two arrays, like the following example.

{
  "ThingsPiratesSay": [
    {
      "say": "Avast!"
    },
    {
      "say": "Yar!"
    },
    {
      "say": "Walk the Plank!"
    }
  ],
  "ThingsGiantsSay": [
    {
      "say": "Fee!"
    },
    {
      "say": "Fi!"
    },
    {
      "say": "Fo!"
    },
    {
      "say": "Fum!"
    }
  ]
}

In this case, you could specify which array to use for Map state iterations by selecting it with ItemsPath. The following state machine definition specifies theThingsPiratesSay array in the input usingItemsPath.It then runs an iteration of the SayWord pass state for each item in theThingsPiratesSay array.

{
  "StartAt": "PiratesSay",
  "States": {
    "PiratesSay": {
      "Type": "Map",
      "ItemsPath": "$.ThingsPiratesSay",
      "ItemProcessor": {
         "StartAt": "SayWord",
         "States": {
           "SayWord": {
             "Type": "Pass",
             "End": true
           }
         }
      },
      "End": true
    }
  }
}

When processing input, theMap state appliesItemsPath after InputPath. It operates on the effective input to the state afterInputPath filters the input.

For more information on Map states, see the following: