json-schema-ref-parser-kmp

JSON Schema $Ref Parser for Kotlin Multiplatform

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JSON Schema $Ref Parser for JVM and Node.js

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Parse, resolve, and dereference JSON Schema $ref pointers on the JVM and Node.js.

This library is the Kotlin Multiplatform evolution of json-schema-ref-parser-jvm. It provides:

  • RefParser as the primary API for Kotlin and Node.js integrations
  • JavaRefParser as the blocking JVM facade for Java and Kotlin/JVM callers
  • a JVM compatibility layer for existing $RefParser and $Refs users
  • JS exports for Node.js runtimes

Project Status

This is the library to choose for new JVM and Node.js integrations.

  • New users should start with json-schema-ref-parser-kmp.
  • Existing json-schema-ref-parser-jvm users can migrate incrementally using the JVM compatibility layer.
  • The $RefParser API remains available on the JVM for compatibility, but it is not the primary API going forward.

Current status:

  • The Kotlin Multiplatform core is working and is intended to match the JVM implementation behavior.
  • The main API has been reshaped around RefParser.
  • Circular reference handling has been reworked in the new implementation and still benefits from broader real-world validation.

The Problem

If you work with JSON Schema, OpenAPI, or AsyncAPI specifications, you know the pain: schemas spread across multiple files, $ref pointers everywhere, and yet another ad hoc parser seems inevitable.

This library handles all of that for you. It is a full JSON Reference and JSON Pointer implementation that crawls even complex schemas and returns a simple object tree with source locations and resolved ref tracking.

Quick Start

Kotlin with RefParser

val doc = RefParser("path/to/openapi.yml")
    .dereference()
    .mergeAllOf()
    .getParsedDocument()

val schema: Map<String, Any?> = doc.schema

Java with JavaRefParser

For blocking callers on the JVM, use the JavaRefParser facade built on top of RefParser.

import io.zenwave360.jsonrefparser.JavaRefParser;
import io.zenwave360.jsonrefparser.model.ParsedDocument;
import java.io.File;
import java.util.Map;

File file = new File("src/main/resources/openapi.yml");

ParsedDocument doc = JavaRefParser.from(file)
        .dereference()
        .mergeAllOf()
        .getParsedDocument();

Map<String, Object> schema = (Map<String, Object>) doc.getSchema();

Node.js

import { dereferenceSchema } from "@zenwave360/json-schema-ref-parser-kmp";

const doc = await dereferenceSchema("file:///workspace/openapi.yml", true);
console.log(doc.schema);

Installation

Java and Kotlin on the JVM

Gradle:

dependencies {
    implementation("io.zenwave360.jsonrefparser:json-schema-ref-parser-kmp-jvm:<version>")
}

Maven:

<dependency>
  <groupId>io.zenwave360.jsonrefparser</groupId>
  <artifactId>json-schema-ref-parser-kmp-jvm</artifactId>
  <version>${json-schema-ref-parser-kmp-jvm.version}</version>
</dependency>

Kotlin Multiplatform

dependencies {
    implementation("io.zenwave360.jsonrefparser:json-schema-ref-parser-kmp:<version>")
}

Node.js

The Node.js API is available from the JS target exports:

  • parseSchemaText(input, baseUri?)
  • dereferenceSchema(uri, mergeAllOf?)
  • dereferenceSchemaText(input, baseUri?, mergeAllOf?)

The npm package name is @zenwave360/json-schema-ref-parser-kmp. npm publishing is not enabled yet, so this repository currently publishes Maven Central artifacts only.

Usage

RefParser Primary API

RefParser is the main suspend-first API for Kotlin and Node.js integrations. Blocking callers on the JVM should use JavaRefParser.

Dereference

Resolves all $ref pointers and replaces them inline, including references to external files and remote URLs.

val doc = RefParser("path/to/schema.yml")
    .dereference()
    .getParsedDocument()

Merge allOf

After dereferencing, merges every allOf array into its parent object, combining fields such as properties and required.

val doc = RefParser("path/to/schema.yml")
    .dereference()
    .mergeAllOf()
    .getParsedDocument()

Circular references

By default, circular references are resolved by preserving object identity. You can also skip them or fail fast.

val doc = RefParser(
    uri = "path/to/schema.yml",
    options = RefParserOptions(onCircular = OnCircular.SKIP),
).dereference().getParsedDocument()

println(doc.hasCircularRefs) // true

Missing references

val doc = RefParser(
    uri = "path/to/schema.yml",
    options = RefParserOptions(onMissing = OnMissing.SKIP),
).dereference().getParsedDocument()

Authentication for remote files

val doc = RefParser(
    uri = "path/to/schema.yml",
    auth = listOf(
        AuthenticationValue(
            key = "Authorization",
            value = "Bearer <token>",
            urlMatcher = { url -> url.contains("api.example.com") },
        )
    ),
).dereference().getParsedDocument()

Loader configuration

Replace the loader chain completely:

val doc = RefParser("classpath:/schemas/openapi.yml")
    .withLoaders(
        ClasspathLoader(pluginClassLoader),
        FileLoader(),
        HttpLoader(),
    )
    .dereference()
    .getParsedDocument()

Patch only the default chain, replacing matching loader types and preserving the rest:

val doc = RefParser("classpath:/schemas/openapi.yml")
    .withDefaultLoaders(
        ClasspathLoader(pluginClassLoader),
    )
    .dereference()
    .getParsedDocument()

Classpath loading on the JVM

val doc = RefParser("classpath:/schemas/openapi.yml")
    .dereference()
    .getParsedDocument()

Source locations

Every node in the parsed document carries its original file and line and column range, even after dereferencing across multiple files.

val doc = RefParser("path/to/schema.yml")
    .dereference()
    .getParsedDocument()

val location = doc.locations["/info"]
println("${location?.file}:${location?.line}:${location?.column}")

Original ref tracking

After dereferencing, you can look up which $ref string a given object came from.

val doc = RefParser("path/to/schema.yml")
    .dereference()
    .getParsedDocument()

val ref = doc.getOriginalRef(someSchemaObject)
println(ref?.refString) // e.g. "#/components/schemas/Pet"

Loading from a string

Useful in tests or when you already have the document text in memory.

val yaml = """
    type: object
    properties:
      name:
        type: string
""".trimIndent()

val doc = RefParser.fromText(yaml).dereference().getParsedDocument()

Java on the JVM

Blocking JVM callers should use the JVM facade:

import io.zenwave360.jsonrefparser.JavaRefParser;
import io.zenwave360.jsonrefparser.model.OnCircular;
import io.zenwave360.jsonrefparser.model.OnMissing;
import io.zenwave360.jsonrefparser.model.ParsedDocument;
import io.zenwave360.jsonrefparser.model.RefParserOptions;
import java.io.File;

File file = new File("src/main/resources/openapi.yml");

ParsedDocument doc = JavaRefParser.from(file)
        .withOptions(new RefParserOptions(OnCircular.SKIP, OnMissing.FAIL))
        .dereference()
        .mergeAllOf()
        .getParsedDocument();

System.out.println(doc.getSchema());

Patch only the default classpath loader while keeping the default file and HTTP loaders:

import io.zenwave360.jsonrefparser.JavaRefParser;
import java.net.URI;

var doc = JavaRefParser.from(URI.create("classpath:catalog/service/asyncapi.yml"))
        .withResourceClassLoader(pluginClassLoader)
        .dereference()
        .getParsedDocument();

Patch the default loader chain explicitly:

import io.zenwave360.jsonrefparser.JavaRefParser;
import io.zenwave360.jsonrefparser.io.ClasspathLoader;
import java.util.Arrays;

var doc = JavaRefParser.from("classpath:catalog/service/asyncapi.yml")
        .withDefaultLoaders(Arrays.asList(
                new ClasspathLoader(pluginClassLoader)
        ))
        .dereference()
        .getParsedDocument();

Replace the loader chain completely:

import io.zenwave360.jsonrefparser.JavaRefParser;
import io.zenwave360.jsonrefparser.io.ClasspathLoader;
import io.zenwave360.jsonrefparser.io.FileLoader;
import io.zenwave360.jsonrefparser.io.HttpLoader;
import java.util.Arrays;

var doc = JavaRefParser.from("classpath:catalog/service/asyncapi.yml")
        .withLoaders(Arrays.asList(
                new ClasspathLoader(pluginClassLoader),
                new FileLoader(),
                new HttpLoader()
        ))
        .dereference()
        .getParsedDocument();

$Ref Compatibility API on the JVM

The JVM module still ships the legacy compatibility API for existing json-schema-ref-parser-jvm users:

  • $RefParser
  • $Refs
  • $Ref
  • $RefParserOptions

Use this when you want a low-friction migration path from the old JVM library. For new JVM code, prefer JavaRefParser.

import static io.zenwave360.jsonrefparser.$RefParserOptions.OnCircular.SKIP;

import io.zenwave360.jsonrefparser.$RefParser;
import io.zenwave360.jsonrefparser.$RefParserOptions;
import io.zenwave360.jsonrefparser.$Refs;
import java.io.File;

File file = new File("src/main/resources/openapi.yml");

$Refs refs = new $RefParser(file)
        .withOptions(new $RefParserOptions().withOnCircular(SKIP))
        .dereference()
        .mergeAllOf()
        .getRefs();

Object schema = refs.schema();

Source locations with $Refs

import io.zenwave360.jsonrefparser.$RefParser;
import java.io.File;

File file = new File("src/main/resources/openapi.yml");

var range = new $RefParser(file)
        .parse()
        .getRefs()
        .getJsonLocationRange("$.info");

Node.js

The JS target exports plain object APIs designed for ESM runtimes in Node.js.

Dereference a file:

import { dereferenceSchema } from "@zenwave360/json-schema-ref-parser-kmp";

const doc = await dereferenceSchema("file:///workspace/openapi.yml", true);

console.log(doc.hasCircularRefs);
console.log(doc.locations["/info"]);

Dereference in-memory text:

import { dereferenceSchemaText } from "@zenwave360/json-schema-ref-parser-kmp";

const yaml = `
type: object
properties:
  pet:
    $ref: "#/definitions/Pet"
definitions:
  Pet:
    type: object
    properties:
      name:
        type: string
`;

const doc = await dereferenceSchemaText(yaml, "memory://pet.yml", true);
console.log(doc.schema);

Parse without dereferencing:

import { parseSchemaText } from "@zenwave360/json-schema-ref-parser-kmp";

const doc = parseSchemaText("{\"type\":\"object\"}", "memory://schema.json");
console.log(doc.locations[""]);

Features

  • Parses JSON, YAML, and Avro schemas, or any mix of them
  • Dereferences $ref pointers into a plain object tree
  • Cross-file references: local files, remote URLs, and classpath resources on the JVM
  • Object identity: two $ref pointers to the same target resolve to the same object instance
  • Source locations for every parsed node
  • Original ref tracking for resolved objects
  • Merges allOf arrays into a single object
  • Authentication headers and query parameters for remote loading
  • Circular reference detection with resolve, skip, and fail modes
  • Missing reference handling with skip and fail modes
  • JVM and Node.js support through Kotlin Multiplatform
  • JVM compatibility layer for existing json-schema-ref-parser-jvm users

Release

Maven Central publishing is handled by GitHub Actions. Repository prerequisites and the release sequence are documented in RELEASING.md.

License

JSON Schema $Ref Parser KMP is free and open-source under the MIT license.