Here is our scenario. 

We have added an API by importing OpenAPI 3.0 specification yaml file. We would like to validate the incoming message against the message definition. We are trying to use the validate policy. We configured the policy to validate the incoming JSON message against Definition and then selected the required definition from the dropdown menu. 

We get below error - 

{"httpCode":"400","httpMessage":"Bad Request","moreInformation":"Validate: Instance is neither parsed XML, parsed JSON nor parsed GraphQL"}

Is there anything wrong that we are doing ? Did we miss anything? 

Hi Sandeepkumar,

Do you have a parse policy as your first assembly policy?  request.body is unparsed which would be causing this type of error.  message.body will be created by the parse policy and will be consumed by the validate policy.
Best Regards,

Steve Linn

Thank  you Steve. It is working as expected. 

Hi steve,

could you advise ,I used parse assembly with these configurations :

while it returns this error in the logs :  For Assembly Action 'switch-sit-env_sit-catalog_mw_chld_get_virt_card_denom_1.0.0_parse_0', cannot find the specified variable 'request.body' in the API context. 

version: 2.0.0
    title: Parse JSON Payload
    description: Parses the incoming JSON payload
    use-content-type: true
    document_type: JSON
    input: request.body
    output: parsedPayload

Hi Basma,
The parse policy only needs the API Gateway context message name.  It will use on input or create on output the .body, so simply remove the .body:

version: 2.0.0
    title: Parse JSON Payload
    description: Parses the incoming JSON payload
    use-content-type: true
    document_type: JSON
    input: request
    output: parsedPayload

Your input will be read from request.body and your output will be written to parsedPayload.body

Regards,
Steve Linn

------------------------------
Steve Linn
Senior Consulting I/T Specialist
IBM
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while it returns this error in the logs :  For Assembly Action 'switch-sit-env_sit-catalog_mw_chld_get_virt_card_denom_1.0.0_parse_0', cannot find the specified variable 'request.body' in the API context. 

version: 2.0.0    title: Parse JSON Payload    description: Parses the incoming JSON payload    use-content-type: true    document_type: JSON    input: request.body    output: parsedPayload