Transforming JSON Data in Ansible Playbooks: A Practical Guide

Learn how to parse and transform JSON data into a structured list in Ansible. This guide uses the `from_json` filter and `json_query` for efficient JSON handling.

Introduction

Modern IT automation often requires handling complex JSON data, whether from APIs, configuration files, or dynamic inputs. Ansible, with its powerful filters like from_json and json_query, provides an elegant way to parse and transform JSON data into actionable formats. This guide walks you through parsing JSON data and transforming it into a structured list in an Ansible playbook.

---

The Scenario

You have a JSON string representing a nested structure, such as:

``json


{
  "results": [
    { "instance": { "guest": { "guestState": "running" } }, "item": "foo" },
    { "instance": { "guest": { "guestState": "running" } }, "item": "bar" },
    { "instance": { "guest": { "guestState": "running" } }, "item": "baz" },
    { "instance": { "guest": { "guestState": "running" } }, "item": "qux" },
    { "instance": { "guest": { "guestState": "running" } }, "item": "quux" }
  ]
}



The goal is to transform this JSON into a structured list:

`yaml


formatted_list:
  - { name: "foo", guestState: "running" }
  - { name: "bar", guestState: "running" }
  - { name: "baz", guestState: "running" }
  - { name: "qux", guestState: "running" }
  - { name: "quux", guestState: "running" }



---

The Playbook

Here’s how you can achieve this transformation:

Ansible Code

`yaml


---
hosts: localhost
  gather_facts: false
  tasks:
    - name: Define Raw JSON String (Example - in real use, this comes from a variable)
      set_fact:
        raw_json_string: >
          {
            "results": [
              { "instance": { "guest": { "guestState": "running" } }, "item": "foo" },
              { "instance": { "guest": { "guestState": "running" } }, "item": "bar" },
              { "instance": { "guest": { "guestState": "running" } }, "item": "baz" },
              { "instance": { "guest": { "guestState": "running" } }, "item": "qux" },
              { "instance": { "guest": { "guestState": "running" } }, "item": "quux" }
            ]
          }

    - name: Parse JSON string to dictionary
      set_fact:
        json_data: "{{ raw_json_string | from_json }}"

    - name: Transform JSON to formatted list
      set_fact:
        formatted_list: "{{ json_data.results | json_query('[].{name: item, guestState: instance.guest.guestState}') }}"

    - name: Display formatted list
      debug:
        msg: "Formatted List: {{ formatted_list }}"



---

Explanation

Key Steps

1. Define Raw JSON String:

- Use the set_fact module to define a raw JSON string.


   - In real scenarios, this JSON could come from an API, a file, or another source.

2. Parse JSON String:

- The from_json filter converts the JSON string into a Python dictionary, enabling further manipulation.



3. Transform JSON Data:

- Use the json_query filter to extract and restructure the JSON.

- Query: [].{name: item, guestState: instance.guest.guestState}.

- Extracts item as name.

- Extracts instance.guest.guestState