A JSON Schema validator implementation. It compiles schema into a validation tree to have validation as fast as possible.

Supported drafts:

• Draft 7 (except optional idn-hostname.json test case)
• Draft 6
• Draft 4 (except optional bignum.json test case)

# Cargo.toml
jsonschema = "0.15"

To validate documents against some schema and get validation errors (if any):

use jsonschema::JSONSchema;
use serde_json::json;

fn main() {
    let schema = json!({"maxLength": 5});
    let instance = json!("foo");
    let compiled = JSONSchema::compile(&schema)
        .expect("A valid schema");
    let result = compiled.validate(&instance);
    if let Err(errors) = result {
        for error in errors {
            println!("Validation error: {}", error);
            println!(
                "Instance path: {}", error.instance_path
            );
        }
    }
}

Each error has an instance_path attribute that indicates the path to the erroneous part within the validated instance. It could be transformed to JSON Pointer via .to_string() or to Vec<String> via .into_vec().

If you only need to know whether document is valid or not (which is faster):

use jsonschema::is_valid;
use serde_json::json;

fn main() {
    let schema = json!({"maxLength": 5});
    let instance = json!("foo");
    assert!(is_valid(&schema, &instance));
}

Or use a compiled schema (preferred):

use jsonschema::JSONSchema;
use serde_json::json;

fn main() {
    let schema = json!({"maxLength": 5});
    let instance = json!("foo");
    // Draft is detected automatically
    // with fallback to Draft7
    let compiled = JSONSchema::compile(&schema)
        .expect("A valid schema");
    assert!(compiled.is_valid(&instance));
}

jsonschema supports basic & flag output styles from Draft 2019-09, so you can serialize the validation results with serde:

use jsonschema::{Output, BasicOutput, JSONSchema};

fn main() {
    let schema_json = serde_json::json!({
        "title": "string value",
        "type": "string"
    });
    let instance = serde_json::json!{"some string"};
    let schema = JSONSchema::options()
        .compile(&schema_json)
        .expect("A valid schema");
    
    let output: BasicOutput = schema.apply(&instance).basic();
    let output_json = serde_json::to_value(output)
        .expect("Failed to serialize output");
    
    assert_eq!(
        output_json, 
        serde_json::json!({
            "valid": true,
            "annotations": [
                {
                    "keywordLocation": "",
                    "instanceLocation": "",
                    "annotations": {
                        "title": "string value"
                    }
                }
            ]
        })
    );
}

This library is functional and ready for use, but its API is still evolving to the 1.0 API.

• Python - See the ./bindings/python directory
• Ruby - a crate by @driv3r
• NodeJS - a package by @ahungrynoob

There is a comparison with other JSON Schema validators written in Rust - jsonschema_valid==0.4.0 and valico==3.6.0.

Test machine i8700K (12 cores), 32GB RAM.

Input values and schemas:

• Zuora OpenAPI schema (zuora.json). Validated against OpenAPI 3.0 JSON Schema (openapi.json).
• Kubernetes Swagger schema (kubernetes.json). Validated against Swagger JSON Schema (swagger.json).
• Canadian border in GeoJSON format (canada.json). Schema is taken from the GeoJSON website (geojson.json).
• Concert data catalog (citm_catalog.json). Schema is inferred via infers-jsonschema & manually adjusted (citm_catalog_schema.json).
• Fast is taken from fastjsonschema benchmarks (fast_schema.json, fast_valid.json and fast_invalid.json).

Here is the average time for each contender to validate. Ratios are given against compiled JSONSchema using its validate method. The is_valid method is faster, but gives only a boolean return value:

Notes:

1. jsonschema_valid and valico do not handle valid path instances matching the ^\\/ regex.

2. jsonschema_valid fails to resolve local references (e.g. #/definitions/definitions).

You can find benchmark code in benches/jsonschema.rs, Rust version is 1.57.

If you have anything to discuss regarding this library, please, join our gitter!