HTTP Query Parameters from JSON

Use case

When integrating with an HTTP or REST API, it is common to set query parameters for API requests. In scenarios where JSON data is in Exchange, specific values from the JSON may need to be extracted and used as query parameters in subsequent HTTP requests. This process involves parsing the JSON to retrieve the necessary values and then incorporating these values into the query string of the HTTP request to ensure proper communication and data retrieval from the API.

Below is an example of the data in Exchange:

{
  "id": "12345",
  "customer": {
    "firstName": "Jane",
    "lastName": "Doe"
  }
}

In this example, we will call a service that estimates the age based on a single name:

https://api.agify.io?name=$NAME

For basic usage, you just need to pass a firsName from our JSON as the name parameter in HTTP service. The service will process the request and return an estimated age for the given name.

Implementation Highlights:

1. Unmarshall JSON to Dynamic Java Object: Use Jackson to convert JSON data to a dynamic Java object, leveraging Jackson's dynamic binding capabilities.
2. Set Query Parameter: Define query paramatest using Exchange variables.
3. Call HTTP Service: Call HTTP Service using defined query parameters

Design

In the following example, we demonstrate how to create an Exchange that starts with a time-based trigger (repeats once) and sets query parameters for an HTTP request using values extracted from a JSON response.

1. Set JSON Example: We start by setting our JSON example to a variable called json.
2. Unmarshall JSON to Java Object: The JSON data is unmarshalled into a Java object stored in a variable named data.
3. Set Header CamelHttpQuery: This is a crucial step where we set the CamelHttpQuery header using Groovy expression language, with values extracted from the data variable.
4. Call HTTP Service: An HTTP service is called using the HTTP component.
5. Log Response: The response from the HTTP service is logged.

YAML

routing.camel.yaml

- route:
    id: route-29bf
    description: Query Param Demo
    nodePrefixId: route-99f
    from:
      id: from-ce44
      description: Start
      uri: timer
      parameters:
        timerName: test
        repeatCount: "1"
      steps:
        - setVariable:
            id: setVariable-ec8d
            description: "Set demo JSON "
            name: json
            expression:
              constant:
                id: constant-c086
                expression: |-
                  {
                    "id": "12345",
                    "customer": {
                      "firstName": "Jane",
                      "lastName": "Doe"
                    }
                  }
        - unmarshal:
            id: unmarshal-a7df
            description: Unmarshal to Object
            variableSend: json
            variableReceive: data
            json:
              id: json-a946
        - setHeader:
            id: setHeader-d181
            description: Set Query Parameter
            name: CamelHttpQuery
            expression:
              groovy:
                id: groovy-8170
                expression: "'name=' + variables.data.customer.firstName"
        - to:
            id: to-81a9
            description: Call HTTP Service
            variableReceive: response
            uri: https
            parameters:
              httpMethod: GET
              httpUri: https://api.agify.io
              throwExceptionOnFailure: false
        - log:
            id: log-2181
            description: Log result
            message: ${variable.response}