JSON Path

KodeKloud

August 10, 2025 - 3 minutes read - 494 words

JSON Path is a query language for JSON data structures, originally created by Stefan Goessner and now maintained as the Jayway JsonPath Java library. It works much like SQL does for relational data: you write an expression to select specific elements from a JSON document using paths, indexes, wildcards, and filter criteria. The resources linked below cover everything from beginner syntax to advanced Java API usage and practical kubectl integration. You’ll find this handy in day-to-day work with Kubernetes as well as when you work with other JSON application outputs. If you are looking for an alternative in the command line, you can install and use jq.

Core Syntax at a Glance

Operator	Meaning	Example
`$`	Root element	`$.store`
`.`	Child access	`$.store.book`
`['key']`	Bracket child access	`$['store']['book']`
`[n]`	Array index	`$.book[0]`
`[a:b]`	Array slice	`$.book[0:2]`
`*`	Wildcard (all children)	`$.store.*`
`..`	Deep scan (recursive)	`$..author`
`[?(expr)]`	Filter predicate	`$.book[?(@.price < 10)]`
`@`	Current item in a filter	`@.color == "blue"`

Quick Examples

Given:

{
  "store": {
    "book": [
      { "title": "Sayings of the Century", "price": 8.95 },
      { "title": "Sword of Honour", "price": 12.99 },
      { "title": "Moby Dick", "price": 8.99 }
    ],
    "bicycle": { "color": "red", "price": 19.95 }
  }
}

Query	Returns
`$.store.book[*].title`	All book titles
`$..price`	Every price in the document
`$.store.book[?(@.price < 10)]`	Books under $10
`$..book[2].title`	“Moby Dick”
`$..book.length()`	`3`

What Is in the Resources

Jayway JsonPath (GitHub)

The Jayway JsonPath repository is the Java implementation of the spec. It covers:

Maven setup and version notes (v3.0.0 requires Java 17)
Full operator and function reference (min, max, avg, sum, length, keys, first, last, index, etc.)
Extended filter operators beyond the basics: =~ (regex), subsetof, anyof, noneof, size, empty
Java API for reading, setting, and modifying JSON documents
Predicate building via inline expressions, the Filter/Criteria API, or custom Predicate implementations
Configuration options like DEFAULT_PATH_LEAF_TO_NULL, ALWAYS_RETURN_LIST, and SUPPRESS_EXCEPTIONS
Multiple JSON providers (JsonSmart, Jackson, Gson, Jakarta) and POJO mapping

KodeKloud Course (PDF)

The attached PDF is a beginner-friendly walkthrough that covers:

YAML vs JSON and why JSON Path targets the JSON form
Dictionaries, lists, and nested structures with visual examples
Criteria and filter expressions step by step
Wildcard usage across objects and arrays
JSON Path in Kubernetes: kubectl examples, range loops, custom columns, and sorting

JSON Path in `kubectl`

This is where JSON Path gets really practical. Instead of dumping raw JSON, you extract exactly what you need.

Note

In kubectl, the $ root is omitted. Queries start with ..

Common Patterns

Goal	Command
All pod names	`kubectl get pods -o=jsonpath='{.items[*].metadata.name}'`
All node CPU counts	`kubectl get nodes -o=jsonpath='{.items[*].status.capacity.cpu}'`
First pod’s image	`kubectl get pods -o=jsonpath='{.items[0].spec.containers[0].image}'`

Formatted Output with `range`

kubectl get nodes -o=jsonpath='{range .items[*]}{.metadata.name}{"\t"}{.status.capacity.cpu}{"\n"}{end}'

master    4
node01    4

Custom Columns

kubectl get nodes -o=custom-columns=NODE:.metadata.name,CPU:.status.capacity.cpu

NODE     CPU
master   4
node01   4

Sorting

kubectl get nodes --sort-by=.metadata.name
kubectl get nodes --sort-by=.status.capacity.cpu

References

📎 Download json-path-course-resource-compressed.pdf