json-schema-validator
This multiplatform library is an implementation of JSON schema that can validate
JsonElement
from kotlinx.serialization-json library.
Usage
Supported targets
Dependencies
Releases
In order to use releases add Maven Central repository to the list of repositories.
Gradle
Kotlin
repositories {
mavenCentral()
}
implementation("io.github.optimumcode:json-schema-validator:0.5.5")
Groovy
repositories {
mavenCentral()
}
implementation 'io.github.optimumcode:json-schema-validator:0.5.5'
// or with BOM
implementation(platform("io.github.optimumcode:json-schema-validator-bom:0.5.5"))
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
repositories {
maven(url = "https://s01.oss.sonatype.org/content/repositories/releases/")
}
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:
<dependency>
<groupId>io.github.optimumcode</groupId>
<artifactId>json-schema-validator-jvm</artifactId>
<version>0.5.1</version>
</dependency>
And you can also add a sonatype repository to your POM file
Snapshots
If you want to use SNAPSHOT version you should add Sonatype Snapshot repository to your build script.
Gradle
Kotlin
repositories {
maven(url = "https://s01.oss.sonatype.org/content/repositories/snapshots")
}
implementation("io.github.optimumcode:json-schema-validator:0.5.6-SNAPSHOT")
implementation(platform("io.github.optimumcode:json-schema-validator-bom:0.5.6-SNAPSHOT"))
implementation("io.github.optimumcode:json-schema-validator")
Groovy
repositories {
maven { url 'https://s01.oss.sonatype.org/content/repositories/snapshots' }
}
implementation 'io.github.optimumcode:json-schema-validator:0.5.6-SNAPSHOT'
Maven
For the Maven you need to add a snapshot repository to your POM file
And then you can add a dependency to a SNAPSHOT version
<dependency>
<groupId>io.github.optimumcode</groupId>
<artifactId>json-schema-validator-jvm</artifactId>
<version>0.5.2-SNAPSHOT</version>
</dependency>
Example
If you have just one JSON schema or many independent schemes
you can create it using factory methods defined on JsonSchema class.
import io.github.optimumcode.json.schema.JsonSchema
import io.github.optimumcode.json.schema.ValidationError
import kotlinx.serialization.json.JsonElement
val key = "\$"
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(),
)
errors = mutableListOf<ValidationError>()
elementToValidate: JsonElement = loadJsonToValidate()
valid = schema.validate(elementToValidate, errors::add)
You can also use predefined ValidationOutputs to collect the results.
Output formats are defined in draft 2020-12.
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).
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.
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": {
"ref": "https://test.com#/properties/name"
}
}
}
""".trimIndent(),
)
errors = mutableListOf<ValidationError>()
elementToValidate: JsonElement = loadJsonToValidate()
valid = schema.validate(elementToValidate, errors::add)
Supported JSON schema drafts:
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 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.
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()
.withSchemaOption(SchemaOption.FORMAT_BEHAVIOR_OPTION, ANNOTATION_AND_ASSERTION)
.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).
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 with information about that library.
There is also an API to implement the user's defined format validation.
The FormatValidator interface can be user for that.
The custom format validators can be register in JsonSchemaLoader.
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.
Compliance to JSON schema test suites
This library uses official JSON schema test suites
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.
NOTE: Python 3.* is required to run test-suites.
It is used to generate list of remote schemas using this script
This library is also integrated into bowtie
and runs against the official test suite along with other libraries.
You can find the report here.
Benchmarking
There is a benchmark project that compares this library with some other ones:
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 in nice charts.
Many thanks to maintainers of 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:
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.
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.
Future plans
License
