# bazaarvoice/jolt

JSON to JSON transformation library written in Java.

Repository: https://github.com/bazaarvoice/jolt
Canonical: https://ross.abutalabs.com/products/jolt
Language: Java
License: Apache-2.0
License Family: permissive
Last push: 2026-08-05T20:34:20+00:00

## Health v2 (maintenance only)
Score: 66/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 96, release rhythm 8, longevity 100
- inputs: {"age_days": 4947, "days_push": 28, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1675, forks 350 (observed 2026-08-28T04:05:20.534254+00:00)

## What it is
Jolt is a Java library for JSON-to-JSON transformation where the transform specification is itself a JSON document. It provides chained stock transforms (shift, default, remove, sort, cardinality) that reshape JSON structure, with extension points for custom Java value manipulation.

## Use cases
- transform JSON responses from Elasticsearch, MongoDB, or Cassandra before exposing them
- reshape API payloads to match another service's expected schema
- extract a subset of fields from large JSON documents
- apply default values to missing JSON fields declaratively
- normalize inconsistent JSON structures like single object vs list cardinality
- define data mappings as JSON specs instead of writing Java mapping code

## When to choose
- you need declarative, spec-driven structural transformation of JSON on the JVM
- you want transform logic that is data (JSON) rather than compiled code
- you need to chain multiple structural operations like shift, default, and remove
- your team wants non-developers to review or edit mapping specs

## When to avoid
- you need heavy per-value computation or business logic inside the transform
- you are not on the JVM and cannot run Java
- you need streaming transformation of very large JSON documents rather than in-memory trees
- you want a visual GUI mapping tool rather than a JSON DSL

## Facets
- artifact type: library
- maturity: stable
- function: serialization, developer-tools
- domain: developer-tools, apis
- platform: jvm, cli
- tags: -transformation, -to-, spec-driven, data-mapping, etl, data-engineering

## Member repositories
- bazaarvoice/jolt (main) score 66

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:05:20.534254+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T03:42:28.672949+00:00, confidence not recorded.
  - readme: https://github.com/bazaarvoice/jolt (fetched 2026-08-28T04:05:20.534254+00:00, sha 444e8d244fa0)
- Data as of 2026-08-30T08:39:29.467469+00:00.