For AWS SNS messages that contain JSON serialized as strings, you'll need to handle two levels of parsing: 1. The outer SNS message structure 2. The inner JSON string that contains your actual data Here's how you can access the JSON data in your webhook using Jinja2: 1. For Simple JSON Fields

jinja2
{{ body.Message }}  {# Access the SNS Message field #}

2. For Parsing Nested JSON String Since AWS SNS typically sends the actual message in the "Message" field as a JSON string, you'll need to use Prefect's built-in

json_loads

filter:

jinja2
{% set parsed_message = body.Message | json_loads %}
{{ parsed_message.your_attribute }}

Here are some practical examples:

jinja2
{# Access basic SNS fields #}
Topic ARN: {{ body.TopicArn }}
Message ID: {{ body.MessageId }}

{# Parse and access the JSON message content #}
{% set data = body.Message | json_loads %}
User ID: {{ data.user_id }}
Status: {{ data.status }}

{# Using default values for safety #}
Status: {{ data.status | default('unknown') }}

Some important tips: 1. Always use the

default

filter when accessing fields that might not exist to prevent template errors:

jinja2
   {{ data.optional_field | default('fallback_value') }}

2. For keys that aren't valid Python identifiers, use bracket notation:

jinja2
   {{ data['special-key-with-hyphens'] }}

3. You can combine multiple filters:

jinja2
   {{ body.Message | json_loads | tojson }}

4. For debugging, you can print the entire parsed structure:

jinja2
   Raw Message: {{ body.Message }}
   Parsed Data: {{ body.Message | json_loads | tojson }}

Remember that the webhook needs to be configured with the correct Content-Type (application/json) to ensure proper JSON parsing of the incoming SNS message. Would you like me to provide more specific examples based on your particular JSON structure or use case?

@Marvin Can you point me to the doc for json_loads?

Based on this research, I need to correct my earlier response. The proper way to handle JSON in Prefect webhooks depends on how the data is being received: 1. If the webhook receives JSON data with the proper Content-Type header, Prefect automatically parses it and makes it available in the

body

variable in your template. 2. For nested JSON strings (like in AWS SNS messages), you might need to handle the parsing in your flow rather than in the webhook template itself, as complex JSON manipulation in webhook templates can be tricky. I recommend one of these approaches: 1. Simple Approach: Pass the raw message to your flow and handle parsing there:

jinja2
{{ body.Message }}  {# Pass the raw message string to your flow #}

Then in your flow:

python
import json

@flow
def handle_sns_message(message: str):
    data = json.loads(message)
    # Now you can work with the parsed JSON

2. Alternative Approach: If you must handle it in the webhook template, you can try using Jinja2's built-in

from_json

filter (if available in your environment):

jinja2
{% set message_data = body.Message | from_json %}
{{ message_data.your_field }}

I apologize for my earlier incorrect suggestion about

json_loads

. Would you like me to provide more specific guidance based on your particular use case or JSON structure?