https://github.com/optimumcode/json-schema-validator
The JSON schema validation library that works with https://github.com/Kotlin/kotlinx.serialization
https://github.com/optimumcode/json-schema-validator
json-schema-validator kotlin kotlin-library multiplatform
Last synced: about 1 year ago
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The JSON schema validation library that works with https://github.com/Kotlin/kotlinx.serialization
- Host: GitHub
- URL: https://github.com/optimumcode/json-schema-validator
- Owner: OptimumCode
- License: mit
- Created: 2023-07-11T09:16:42.000Z (almost 3 years ago)
- Default Branch: main
- Last Pushed: 2025-04-10T15:23:57.000Z (about 1 year ago)
- Last Synced: 2025-04-16T01:16:28.545Z (about 1 year ago)
- Topics: json-schema-validator, kotlin, kotlin-library, multiplatform
- Language: Kotlin
- Homepage:
- Size: 2.34 MB
- Stars: 46
- Watchers: 2
- Forks: 6
- Open Issues: 8
-
Metadata Files:
- Readme: README.md
- Changelog: changelog_config.json
- License: LICENSE
Awesome Lists containing this project
README
# json-schema-validator
[](https://opensource.org/license/mit/)
[](https://json-schema.org/specification)
[](https://app.fossa.com/projects/custom%2B46664%2Fgithub.com%2FOptimumCode%2Fjson-schema-validator?ref=badge_shield&issueType=license)
This multiplatform library is an implementation of JSON schema that can validate
[JsonElement](https://github.com/Kotlin/kotlinx.serialization/blob/master/formats/json/commonMain/src/kotlinx/serialization/json/JsonElement.kt)
from [kotlinx.serialization-json](https://github.com/Kotlin/kotlinx.serialization/tree/master/formats/json) library.
[](https://codespaces.new/OptimumCode/json-schema-validator)
[](https://devpod.sh/open#https://github.com/OptimumCode/json-schema-validator)
## Usage
### Supported targets
| Target |
|-------------------|
| jvm |
| js |
| wasmJs |
| macosX64 |
| macosArm64 |
| iosArm64 |
| iosSimulatorArm64 |
| linuxX64 |
| linuxArm64 |
| mingwX64 |
### Dependencies
#### Releases
In order to use releases add Maven Central repository to the list of repositories.
##### Gradle
###### Kotlin
```kotlin
repositories {
mavenCentral()
}
implementation("io.github.optimumcode:json-schema-validator:0.5.1")
```
###### Groovy
```groovy
repositories {
mavenCentral()
}
implementation 'io.github.optimumcode:json-schema-validator:0.5.1'
// or with BOM
implementation(platform("io.github.optimumcode:json-schema-validator-bom:0.5.1"))
implementation("io.github.optimumcode:json-schema-validator")
```
_Release are published to Sonatype repository. The synchronization with Maven Central takes time._
_If you want to use the release right after the publication you should add Sonatype Release repository to your build script._
###### Kotlin
```kotlin
repositories {
maven(url = "https://s01.oss.sonatype.org/content/repositories/releases/")
}
```
###### Groovy
```groovy
repositories {
maven { url 'https://s01.oss.sonatype.org/content/repositories/releases/' }
}
```
##### Maven
You can also use `json-schema-validator` as a dependency in your maven project.
But Maven cannot use Gradle's metadata so you need to depend on a JVM-specific artifact in your project:
```xml
io.github.optimumcode
json-schema-validator-jvm
0.5.1
```
And you can also add a sonatype repository to your POM file
```xml
sonatype-release
sonatype-release
https://s01.oss.sonatype.org/content/repositories/releases/
false
true
```
#### Snapshots
_If you want to use SNAPSHOT version you should add Sonatype Snapshot repository to your build script._
##### Gradle
###### Kotlin
```kotlin
repositories {
maven(url = "https://s01.oss.sonatype.org/content/repositories/snapshots")
}
implementation("io.github.optimumcode:json-schema-validator:0.5.2-SNAPSHOT")
// or with BOM
implementation(platform("io.github.optimumcode:json-schema-validator-bom:0.5.2-SNAPSHOT"))
implementation("io.github.optimumcode:json-schema-validator")
```
###### Groovy
```groovy
repositories {
maven { url 'https://s01.oss.sonatype.org/content/repositories/snapshots' }
}
implementation 'io.github.optimumcode:json-schema-validator:0.5.2-SNAPSHOT'
```
##### Maven
For the Maven you need to add a snapshot repository to your POM file
```xml
sonatype
sonatype-snapshot
https://s01.oss.sonatype.org/content/repositories/snapshots/
true
false
```
And then you can add a dependency to a SNAPSHOT version
```xml
io.github.optimumcode
json-schema-validator-jvm
0.5.2-SNAPSHOT
```
### Example
If you have just one JSON schema or many independent schemes
you can create it using factory methods defined on `JsonSchema` class.
```kotlin
import io.github.optimumcode.json.schema.JsonSchema
import io.github.optimumcode.json.schema.ValidationError
import kotlinx.serialization.json.JsonElement
val key = "\$" // to use $ in multiline string
val schema = JsonSchema.fromDefinition(
"""
{
"${key}schema": "http://json-schema.org/draft-07/schema#",
"definitions": {
"positiveInteger": {
"type": "integer",
"minimum": 0
}
},
"properties": {
"size": { "${key}ref": "#/definitions/positiveInteger" }
}
}
""".trimIndent(),
)
val errors = mutableListOf()
val elementToValidate: JsonElement = loadJsonToValidate()
val valid = schema.validate(elementToValidate, errors::add)
```
You can also use predefined `ValidationOutput`s to collect the results.
Output formats are defined in [draft 2020-12](https://json-schema.org/draft/2020-12/draft-bhutton-json-schema-01#section-12.4).
The most performance can be achieved by using either `flag` or `basic` collectors.
The `detailed` and `verbose` provide more structured information but this adds additional cost to the validation process
(because they collect hierarchical output).
```kotlin
import io.github.optimumcode.json.schema.JsonSchema
import io.github.optimumcode.json.schema.OutputCollector
import io.github.optimumcode.json.schema.ValidationOutput.Flag
import io.github.optimumcode.json.schema.ValidationOutput.Basic
import io.github.optimumcode.json.schema.ValidationOutput.OutputUnit
val flag: Flag = schema.validate(elementToValidate, OutputCollector.flag())
val basic: Basic = schema.validate(elementToValidate, OutputCollector.basic())
val detailed: OutputUnit = schema.validate(elementToValidate, OutputCollector.detailed())
val verbose: OutputUnit = schema.validate(elementToValidate, OutputCollector.verbose())
```
If you need to use more than one schema, and they have references to other schemas you should use `JsonSchemaLoader` class.
```kotlin
import io.github.optimumcode.json.schema.JsonSchemaLoader
import io.github.optimumcode.json.schema.JsonSchema
import io.github.optimumcode.json.schema.ValidationError
import kotlinx.serialization.json.JsonElement
val schema: JsonSchema = JsonSchemaLoader.create()
.register(
"""
{
"${KEY}id": "https://test.com",
"properties": {
"name": {
"type": "string"
}
}
}
""".trimIndent(),
).fromDefinition(
"""
{
"properties": {
"anotherName": {
"${KEY}ref": "https://test.com#/properties/name"
}
}
}
""".trimIndent(),
)
val errors = mutableListOf()
val elementToValidate: JsonElement = loadJsonToValidate()
val valid = schema.validate(elementToValidate, errors::add)
```
## Supported JSON schema drafts:
- [Draft 7](https://json-schema.org/specification-links.html#draft-7)
Supported keywords
- Core
| Keyword | Status |
|:------------|:----------------------------------------------------------------------------------------------------|
| $id | Supported. $id in sub-schemas are collected as well and can be used in $ref |
| $schema | Supported. Validates if schema is one of the supported schemas. The last supported is used if empty |
| $ref | Supported |
| definitions | Supported. Definitions are loaded and can be referenced |
- Assertions
| Category | Assertion | Status |
|:--------------|:---------------------|:------------------------------------------------------------------------------------------------------------------------------------------------|
| General | type | Supported all type [defined in the specification](https://datatracker.ietf.org/doc/html/draft-handrews-json-schema-validation-01#section-6.1.1) |
| | enum | Supported |
| | const | Supported |
| Numbers | multipleOf | Supported |
| | maximum | Supported |
| | exclusiveMaximum | Supported |
| | minimum | Supported |
| | exclusiveMinimum | Supported |
| Strings | maxLength | Supported |
| | minLength | Supported |
| | pattern | Supported (kotlin.text.Regex is used) |
| Arrays | items | Supported |
| | additionalItems | Supported |
| | maxItems | Supported |
| | uniqueItems | Supported |
| | contains | Supported |
| Objects | maxProperties | Supported |
| | minProperties | Supported |
| | required | Supported |
| | properties | Supported |
| | patternProperties | Supported (kotlin.text.Regex is used) |
| | additionalProperties | Supported |
| | dependencies | Supported |
| | propertyNames | Supported |
| Conditions | if/then/else | Supported |
| Boolean logic | allOf | Supported |
| | anyOf | Supported (all validation will be executed even if the element matches the first one) |
| | oneOf | Supported |
| | not | Supported |
- [Draft 2019-09](https://json-schema.org/specification-links#draft-2019-09-(formerly-known-as-draft-8))
Supported keywords
- Core
| Keyword | Status |
|:------------------|:----------------------------------------------------------------------------------------------------|
| $id | Supported. $id in sub-schemas are collected as well and can be used in $ref |
| $schema | Supported. Validates if schema is one of the supported schemas. The last supported is used if empty |
| $ref | Supported |
| $recursiveRef | Supported |
| $defs/definitions | Supported. Definitions are loaded and can be referenced |
| $vocabulary | Supported. You can disable and enable vocabularies through custom meta-schemes |
- Assertions
| Category | Assertion | Status |
|:--------------|:----------------------|:------------------------------------------------------------------------------------------------------------------------------------------------|
| General | type | Supported all type [defined in the specification](https://datatracker.ietf.org/doc/html/draft-handrews-json-schema-validation-01#section-6.1.1) |
| | enum | Supported |
| | const | Supported |
| Numbers | multipleOf | Supported |
| | maximum | Supported |
| | exclusiveMaximum | Supported |
| | minimum | Supported |
| | exclusiveMinimum | Supported |
| Strings | maxLength | Supported |
| | minLength | Supported |
| | pattern | Supported (kotlin.text.Regex is used) |
| Arrays | items | Supported |
| | additionalItems | Supported |
| | unevaluatedItems | Supported |
| | maxItems | Supported |
| | uniqueItems | Supported |
| | contains | Supported |
| | minContains | Supported (does not affect the work of contains assertion anyhow even if minContains=0) |
| | maxContains | Supported |
| Objects | maxProperties | Supported |
| | minProperties | Supported |
| | required | Supported |
| | properties | Supported |
| | patternProperties | Supported (kotlin.text.Regex is used) |
| | additionalProperties | Supported |
| | unevaluatedProperties | Supported |
| | dependentRequired | Supported |
| | dependentSchemas | Supported |
| | propertyNames | Supported |
| Conditions | if/then/else | Supported |
| Boolean logic | allOf | Supported |
| | anyOf | Supported (all validation will be executed even if the element matches the first one) |
| | oneOf | Supported |
| | not | Supported |
- [Draft 2020-12](https://json-schema.org/specification-links#2020-12)
Supported keywords
- Core
| Keyword | Status |
|:---------------------------|:----------------------------------------------------------------------------------------------------|
| $id | Supported. $id in sub-schemas are collected as well and can be used in $ref |
| $schema | Supported. Validates if schema is one of the supported schemas. The last supported is used if empty |
| $ref | Supported |
| $dynamicRef/$dynamicAnchor | Supported |
| $defs/definitions | Supported. Definitions are loaded and can be referenced |
| $vocabulary | Supported. You can disable and enable vocabularies through custom meta-schemes |
- Assertions
| Category | Assertion | Status |
|:--------------|:----------------------|:------------------------------------------------------------------------------------------------------------------------------------------------|
| General | type | Supported all type [defined in the specification](https://datatracker.ietf.org/doc/html/draft-handrews-json-schema-validation-01#section-6.1.1) |
| | enum | Supported |
| | const | Supported |
| Numbers | multipleOf | Supported |
| | maximum | Supported |
| | exclusiveMaximum | Supported |
| | minimum | Supported |
| | exclusiveMinimum | Supported |
| Strings | maxLength | Supported |
| | minLength | Supported |
| | pattern | Supported (kotlin.text.Regex is used) |
| Arrays | prefixItems | Supported |
| | items | Supported |
| | unevaluatedItems | Supported |
| | maxItems | Supported |
| | uniqueItems | Supported |
| | contains | Supported |
| | minContains | Supported |
| | maxContains | Supported |
| Objects | maxProperties | Supported |
| | minProperties | Supported |
| | required | Supported |
| | properties | Supported |
| | patternProperties | Supported (kotlin.text.Regex is used) |
| | additionalProperties | Supported |
| | unevaluatedProperties | Supported |
| | dependentRequired | Supported |
| | dependentSchemas | Supported |
| | propertyNames | Supported |
| Conditions | if/then/else | Supported |
| Boolean logic | allOf | Supported |
| | anyOf | Supported (all validation will be executed even if the element matches the first one) |
| | oneOf | Supported |
| | not | Supported |
## Thread safety
All public API is thread-safe unless stated otherwise.
Please, read the documentation for each class/interface carefully before using an instance from different threads.
## Format assertion
The library supports `format` assertion.
All formats from [JSON schema draft 2020-12](https://json-schema.org/draft/2020-12/draft-bhutton-json-schema-validation-01#section-7.3) are supported.
According to JSON schema specification the `format` keyword produces **assertion by default** for all drafts **before draft 2019-09**.
Starting **from draft 2019-09** the `format` keyword produces only **annotation by default**.
You can change the default behaviour by specifying the corresponding option in `JsonSchemaLoader`.
```kotlin
import io.github.optimumcode.json.schema.FormatBehavior.ANNOTATION_AND_ASSERTION
import io.github.optimumcode.json.schema.JsonSchemaLoader
import io.github.optimumcode.json.schema.SchemaOption
val schema = JsonSchemaLoader.create()
// option to change the default behavior
.withSchemaOption(SchemaOption.FORMAT_BEHAVIOR_OPTION, ANNOTATION_AND_ASSERTION)
// or
.withSchemaOption(SchemaOption.FORMAT_BEHAVIOR_OPTION, ANNOTATION_ONLY)
.fromDefinition(schemaDefinition)
```
Alternatively, for drafts starting from the draft 2019-09 you can either use a custom meta-schema with format-assertion vocabulary enabled
and use this meta-schema in `$schema` property or define `$vocabulary` block with enabled format assertion in your schema.
**_Implementation details:_**
+ **regex** - to implement regex format Kotlin `Regex` class is used.
Because of that, result might vary depending on the platform where validation is executed
([KT-49557](https://youtrack.jetbrains.com/issue/KT-49557)).
Please, be aware of it when using this library.
If you know a KMM library that provides support for ECMA-262 Regex format
I would appreciate it if you could find some time to create [an issue](https://github.com/OptimumCode/json-schema-validator/issues/new/choose) with information about that library.
There is also an API to implement the user's defined format validation.
The [FormatValidator](src/commonMain/kotlin/io/github/optimumcode/json/schema/ValidationError.kt) interface can be user for that.
The custom format validators can be register in [JsonSchemaLoader](src/commonMain/kotlin/io/github/optimumcode/json/schema/JsonSchemaLoader.kt).
_**Please note, that the format validation API is marked as experimental and will require `OptIn` declaration in your code.**_
## Custom assertions
You can implement custom assertions and use them. Read more [here](docs/custom_assertions.md).
## Compliance to JSON schema test suites
This library uses official [JSON schema test suites](https://github.com/json-schema-org/JSON-Schema-Test-Suite)
as a part of the CI to make sure the validation meet the expected behavior.
Not everything is supported right now but the missing functionality might be added in the future.
The tests are located [here](test-suites).
**NOTE:** _Python 3.* is required to run test-suites._
_It is used to generate list of remote schemas using [this script](test-suites/schema-test-suite/bin/jsonschema_suite)_
This library is also integrated into [bowtie](https://github.com/bowtie-json-schema/bowtie)
and runs against the official test suite along with other libraries.
You can find the report [here](https://bowtie.report/).
[](https://bowtie.report/#/dialects/draft4?language=kotlin)
[](https://bowtie.report/#/dialects/draft6?language=kotlin)
[](https://bowtie.report/#/dialects/draft7?language=kotlin)
[](https://bowtie.report/#/dialects/draft2019-09?language=kotlin)
[](https://bowtie.report/#/dialects/draft2020-12?language=kotlin)
## Benchmarking
There is a benchmark project that compares this library with some other ones:
+ [OpenAPI schema validator](https://github.com/openapi-processor/openapi-parser/tree/master/json-schema-validator)
+ [Networknt Schema Validator](https://github.com/networknt/json-schema-validator)
The benchmark is scheduled to run every night on Monday.
You can see the results in the latest workflow execution.
Also, benchmark results are available [here](https://optimumcode.github.io/json-schema-validator/dev/bench/) in nice charts.
Many thanks to maintainers of [github-action-benchmark](https://github.com/benchmark-action/github-action-benchmark) repo.
## Developer notes
### Build process
The update to Kotlin 1.9.22 came with an issue for JS incremental compilation.
In case you see an error about main function that already bind please execute `clean` task.
When you build project for **linux** target you might get an error about missing native library.
This is because `com.doist.x:normalize` requires this library to perform string normalization.
This is needed to support `idn-hostname` format. Install this library with the following command:
```bash
sudo apt-get install -y libunistring-dev
```
### Devcontainer
Devcontainers is a cool feature. However, by default in Codespaces and DevPod you will use [VS Code](https://code.visualstudio.com/).
This is a good IDE but not for Kotlin, unfortunately.
The extension that is available for VS Code to support Kotlin works quite slow (when workspace is just started)
and sometimes does not work correctly with multiplatform definitions.
Because of that I higly recoment using JetBrains Gateway
(but it looks like the GitHub Codespace provider is not currently compatible with latest Gateway version).
However, there is a way to connect to Codespace and work with project using JetBrains IDE.
Please, read details [here](docs/codespaces_for_jetbrains.md).
## Future plans
- [x] Add `$schema` property validation (if not set the latest supported will be used)
- [x] Add proper `$id` support (for nested schemas and for referencing)
- [x] Add support for newer drafts
- [x] [Draft 2019-09 (Draft 8)](https://json-schema.org/specification-links.html#draft-2019-09-formerly-known-as-draft-8)
- [x] [2020-12](https://json-schema.org/specification-links.html#2020-12)
- [x] Add support for schemas from external documents
- [x] Load schemas from local sources
- [ ] Load schemas from remote sources
- [x] Formalize error output as it is defined in the latest drafts
## License
[](https://app.fossa.com/projects/custom%2B46664%2Fgithub.com%2FOptimumCode%2Fjson-schema-validator?ref=badge_large&issueType=license)