Hi
Hope this finds you well.

We have the following requirements for which expert opinion is required. 

1. Retrieve the query parameter: We have achieved it through "$(request.parameters.state)" where the state is the name of one of the query parameters.

2. We want to pass the value of the query parameter retrieved in step 1 as JSON object in body. or

3. We want to convert the query parameter into json object 

4. Access the json data from the object and evaluate the substring function as substring is JSONata expression and can be only applied to json data.This we have achieved through foloowing code 

Hi Pragnesh,
For something simple, the set variable policy may work.  I'm assuming since you're saying AWS base plan you don't have the GatewayScript policy which would definitely be the preferred choice if it was available.

For my quick test

curl -k https://w.x.y.z:7444/swlinnorg/sandbox/test-query-to-json/path-1?state=1234567890
{"state": "1234567890"}

Was accomplished with this API assembly

  assembly:
    execute:
      - set-variable:
          version: 2.0.0
          title: set-variable
          actions:
            - set: message.body
              value: '{"state": "$(request.parameters.state)"}'
              type: any
            - set: message.headers.content-type
              value: application/json
              type: string

Note if you want to subsequently do something with message.body.state, I believe message.body may be a string and if so, you'll need to parse it first.

Obviously, the more complex the object you want to build the less readable the set-variable policy action value property will be.
Best Regards,
Steve

Hi Steve
Thanks for the input. As per your input we have tried the things but while accessing the message.body.state we are getting blank value. 

-> please find below the steps we want to achieve and how we have written the same in YAML file.

1. Retrieve the query parameter:

-> We have achieved through the following assembly :

execute:

- set-variable:

version: 2.0.0

title: Account Information

description: Account Information

actions:

- set: message.headers.state

value: $(request.parameters.state)

type: string

2. We want to pass the value of the query parameter retrieved in step 1 as JSON object in body

-> We tried this with the following assembly

execute:

- set-variable:

version: 2.0.0

title: Account Information

description: Account Information

actions:

- set: message.body

value: '{"state": "$(request.parameters.state)"}'

type: any

3. Access the json data from the object and evaluate the substring function as substring is JSONata expression and can be only applied to json data.This we have achieved through foloowing code

- extract:

version: 2.0.0

title: extract

root: message.body

extracts:

- capture: $.state

transform: $substring($,-4)

description: Include only the last 4 characters of the field.

4. then we tried to access the json data filed and tried to set in the header

- set-variable:

version: 2.0.0

title: Account Information

description: Account Information

actions:

- set: message.headers.state

value: $(message.body.state)

type: string

We are getting the value of message.headers.state as null or empty value.

Do let us know if any other information is required from our end. Looking forward to hearing from you.

Note: The above assembly we are trying for GET operation.

Thanks and Regards

Pragnesh Gandhi

  assembly:    execute:      - set-variable:          version: 2.0.0          title: set-variable          actions:            - set: message.body              value: '{"state": "$(request.parameters.state)"}'              type: any            - set: message.headers.content-type              value: application/json              type: string