AWS CDK Events Add Target with Input Template-CodePudding

I am creating an event in AWS that when a file is dropped into S3, this rule is triggered and starts a step function (SfnStateMachine)

I have some cdk code (node.js) where I add the SfnStateMachine as a target of that rule.

I want to take the payload of the S3 event and use inputPathsMap to map to a readable format, then I can use the inputTemplate to set the payload that will be sent to the Step Function.

 const inputTemplate = {
    Payload: {
      TriggerType: "<detailType>",
      TriggerReason: "<reason>",
      Version: "<versionId>"
    },
  }


rule.addTarget(new events_targets.SfnStateMachine(mystateMachine.stateMachine, {
  input: events.RuleTargetInput.fromObject({ 
    inputPathsMap: {
      detailType: "$.detail-type", 
      reason:"$.detail.reason",
      versionId:"$.detail.object.version-id"
    },
    inputTemplate: JSON.stringify(inputTemplate) }),
  role,
}))

When I use this, it is literally sending the value within withObject

I have looked at the docs and the RuleTargetInput.bind() seems like what I want to use, but I can't see an example of how its used. https://docs.aws.amazon.com/cdk/api/v1/docs/@aws-cdk_aws-events.RuleTargetInput.html

I wanted to do something like

rule.addTarget(new events_targets.SfnStateMachine(ddStateMachine.stateMachine, {
  input: events.RuleTargetInput.bind(),
  role,
}))

but I don't know where to set the inputTemplate or the inputPathsMap because they are the return type rather than the input.

CodePudding user response：

Use the EventField helpers to define input, which defines the Step Function payload:

rule.addTarget(
  new events_targets.SfnStateMachine(ddStateMachine.stateMachine, {
    input: events.RuleTargetInput.fromObject({
      detailType: events.EventField.detailType,
      reason: events.EventField.fromPath("$.detail.reason"),
      versionId: events.EventField.fromPath("$.detail.object.version-id"),
    }),
    role,
  })
);

Building the InputPathMap and InputTemplate is a job for the CDK. The event target construct's synthesized output in the Rule > Targets resource definition is:

"InputTransformer": {
  "InputPathsMap": {
    "detail-type": "$.detail-type",
    "detail-reason": "$.detail.reason",
    "detail-object-version-id": "$.detail.object.version-id"
  },
  "InputTemplate": "{\"detailType\":<detail-type>,\"reason\":<detail-reason>,\"versionId\":<detail-object-version-id>"