JSON PATH 2 Wild Cards

Welcome to this comprehensive guide on using the JSONPath wildcard (*) operator. In this lesson, you’ll discover how to apply wildcards to both JSON objects and arrays, and how to combine them for powerful queries.

Wildcards in JSON Objects

Imagine you have a JSON document with two top-level entries, car and bus, each containing color and price properties:

{
  "car": {
    "color": "blue",
    "price": "$20,000"
  },
  "bus": {
    "color": "white",
    "price": "$120,000"
  }
}

• Expression: $.*.color
  Result: ["blue","white"]

• Expression: $.*.price
  Result: ["$20,000","$120,000"]

Wildcards in JSON Arrays

Next, consider a simple list of wheel objects:

[
  { "model": "X345ERT", "location": "front-right" },
  { "model": "X346ERT", "location": "front-left"  },
  { "model": "X347ERT", "location": "rear-right"  },
  { "model": "X348ERT", "location": "rear-left"   }
]

• Expression: $[*].model
  Result: ["X345ERT","X346ERT","X347ERT","X348ERT"]

Combining Wildcards with Property Access

You can mix object wildcards and array wildcards for nested structures. Here’s a JSON object where each vehicle has a wheels array:

{
  "car": {
    "color": "blue",
    "price": 20000,
    "wheels": [
      { "model": "X345ERT" },
      { "model": "X346ERT" }
    ]
  },
  "bus": {
    "color": "white",
    "price": 120000,
    "wheels": [
      { "model": "Z227KLJ" },
      { "model": "Z226KLJ" }
    ]
  }
}

• Expression: $.*.wheels[*].model
  Result: ["X345ERT","X346ERT","Z227KLJ","Z226KLJ"]

Tips for Building Complex JSONPath Queries

1. Break your expression into smaller parts:
   • Test one branch (e.g., $.car.wheels[*].model).
   • Then test another (e.g., $.bus.wheels[*].model).
2. Once each part works, combine them with wildcards:
   • Final: $.*.wheels[*].model
3. Use online JSONPath evaluators to verify results interactively.

Further Reading and Tools

• JSONPath Specification: https://goessner.net/articles/JsonPath/
• JSONPath Evaluator: https://jsonpath.com/
• Kubernetes JSONPath Guide for real-world examples

Practice creating your own JSONPath expressions with wildcards to master complex data extraction scenarios!