Powertools JMESPath support

JMESPath is a query language for JSON used by AWS CLI, AWS Python SDK, and Powertools for AWS Lambda.

With built-in JMESPath functions to easily deserialize common encoded JSON payloads in Lambda functions.

Key features

• Deserialize JSON from JSON strings, base64, and compressed data
• Use JMESPath to extract and combine data recursively
• Provides commonly used JMESPath expression with popular event sources

JMESPath allows you to transform a JsonDocument into another JsonDocument.

For example, consider the JSON data

string jsonString = """
{
    "body": "{\"customerId\":\"dd4649e6-2484-4993-acb8-0f9123103394\"}",
    "deeply_nested": [
        {
            "some_data": [
                1,
                2,
                3
            ]
        }
    ]
}
""";

using JsonDocument doc = JsonDocument.Parse(jsonString);

string expr = "powertools_json(body).customerId";
//also works for fetching and flattening deeply nested data
// string expr = "deeply_nested[*].some_data[]";

JsonDocument result = JsonTransformer.Transform(doc.RootElement, expr);

It produces the result

"dd4649e6-2484-4993-acb8-0f9123103394"

You can find more examples here

Built-in envelopes

We provide built-in envelopes for popular AWS Lambda event sources to easily decode and/or deserialize JSON objects.

Envelop	JMESPath expression
API_GATEWAY_HTTP	powertools_json(body)
API_GATEWAY_REST	powertools_json(body)
CLOUDWATCH_LOGS	awslogs.powertools_base64_gzip(data) | powertools_json(@).logEvents[*]
KINESIS_DATA_STREAM	Records[*].kinesis.powertools_json(powertools_base64(data))
SNS	Records[*].Sns.Message | powertools_json(@)
SQS	Records[*].powertools_json(body)

More examples of events can be found here

Built-in JMESPath functions

You can use our built-in JMESPath functions within your envelope expression. They handle deserialization for common data formats found in AWS Lambda event sources such as JSON strings, base64, and uncompress gzip data.

powertools_json function

Use powertools_json function to decode any JSON string anywhere a JMESPath expression is allowed.

powertools_base64 function

Use powertools_base64 function to decode any base64 data.

powertools_base64_gzip function

Use powertools_base64_gzip function to decompress and decode base64 data.

Credit

We took heavy inspiration in the https://github.com/danielaparker/JsonCons.Net repository.