Using CloudWatch Event : How to Pass JSON Object to CodeBuild as an Environment Variable - amazon-web-services

Question

Summary: I can't specify a JSON object using CloudWatch target Input Transformer, in order to pass the object contents as an environment variable to a CodeBuild project.
Background:
I trigger an AWS CodeBuild job when an S3 bucket receives any new object. I have enabled CloudTrail for S3 operations so that I can use a CloudWatch rule that has my S3 bucket as an Event Source, with the CodeBuild project as a Target.
If I setup the 'Configure input' part of the Target, using Input Transformer, I can get single 'primitive' values from the event using the format below:
Input path textbox:
{"zip_file":"$.detail.requestParameters.key"}
Input template textbox:
{"environmentVariablesOverride": [ {"name":"ZIP_FILE", "value":<zip_file>}]}
And this works fine if I use 'simple' single strings.
However, for example, if I wish to obtain the entire 'resources' key, which is a JSON object, I need to have knowledge of each of the keys within, and the object structure, and manually recreate the structure for each key/value pair.
For example, the resources element in the Event is:
"resources": [
{
"type": "AWS::S3::Object",
"ARN": "arn:aws:s3:::mybucket/myfile.zip"
},
{
"accountId": "1122334455667799",
"type": "AWS::S3::Bucket",
"ARN": "arn:aws:s3:::mybucket"
}
],
I want the code in the buildspec in CodeBuild to do the heavy lifting and parse the JSON data.
If I specify in the input path textbox:
{"zip_file":"$.detail.resources"}
Then CodeBuild project never gets triggered.
Is there a way to get the entire JSON object, identified by a specific key, as an environment variable?

Answer 1

Check this...CodeBuild targets support all the parameters allowed by StartBuild API. You need to use environmentVariablesOverride in your JSON string.
{"environmentVariablesOverride": [ {"name":"ZIPFILE", "value":<zip_file>}]}
Please,avoid using '_' in the environment name.