Javascript example of meta-schema v1

A Javascript example for validating payloads with instances of the Amazon Product Type Definition Meta-Schema.

Example Validator Implementation for Javascript

For JavaScript applications, the Hyperjump - JSON Schema Validator library supports JSON Schema Draft 2019-09 and custom vocabularies. The following example uses Node.js to demonstrate how to utilize the Hyperjump - JSON Schema Validator library to validate payloads with instances of the Amazon Product Type Definition Meta-Schema. The following example code will not work in a web browser, however, the library does not have dependencies on Node.js and can be used in a web browser. There is no requirement to use this specific library or the example implementation. Amazon does not provide technical support for third-party JSON Schema libraries and this is provided as an example only.

Schema Configuration

When using the Hyperjump - JSON Schema Validator to validate instances of the Amazon Product Type Definition Meta-Schema with custom vocabulary, the meta-schema is configured as a JsonSchema instance with custom vocabulary keyword validation registered in the Hyperjump - JSON Schema Core.

Constants:

// $id of the Amazon Product Type Definition Meta-Schema.
const schemaId = "https://schemas.amazon.com/selling-partners/definitions/product-types/meta-schema/v1";
// $id of the Amazon Product Type Definition Luggage-Schema.
const luggageSchemaId = "https://schemas.amazon.com/selling-partners/definitions/product-types/schema/v1/LUGGAGE";

// Local copy of the Amazon Product Type Definition Meta-Schema.
const metaSchemaPath = "./amazon-product-type-definition-meta-schema-v1.json";

// Local copy of an instance of the Amazon Product Type Definition Meta-Schema.
const luggageSchemaPath = "./luggage.json";

Configure Meta-Schema:

// Add custom vocabulary and keywords
const { Core, Schema } = require("@hyperjump/json-schema-core");
const maxUniqueItemsKeyword = require("./keywords/MaxUniqueItemsKeyword.js");
const maxUtf8ByteLengthKeyword = require("./keywords/MaxUtf8ByteLengthKeyword.js");
const minUtf8ByteLengthKeyword = require("./keywords/MinUtf8ByteLengthKeyword.js");
const customVocabularyId = "https://schemas.amazon.com/selling-partners/definitions/product-types/vocabulary/v1";

// Configure $vocabulary defined in the schema JSON as vocabularyToken
Schema.setConfig(schemaId, "vocabularyToken", "$vocabulary");

// Add custom vocabulary and keywords
Core.defineVocabulary(customVocabularyId, {
    maxUniqueItems : maxUniqueItemsKeyword,
    minUtf8ByteLength : minUtf8ByteLengthKeyword,
    maxUtf8ByteLength : maxUtf8ByteLengthKeyword
});

// Add local schema JSON in JsonSchema.add() to use local copies of schemas rather than retrieving them from the web.
const JsonSchema = require("@hyperjump/json-schema");

// Add meta schema
const metaSchemaJSON = JSON.parse(fs.readFileSync(metaSchemaPath), "utf8");
JsonSchema.add(metaSchemaJSON, schemaId);

// Add luggage schema
const luggageSchemaJSON = JSON.parse(fs.readFileSync(luggageSchemaPath), "utf8");
JsonSchema.add(luggageSchemaJSON, luggageSchemaId, schemaId);

Load Meta-Schema Instance:

// Retrieve previously added luggage schema from JsonSchema instance
var luggageSchema = await JsonSchema.get(luggageSchemaId);

Payload Validation

With an instance of the Amazon Product Type Definition Meta-Schema loaded as a JsonSchema instance, payloads can be validated using the instance.

// Load JSON for the payload (this can be constructed in code, read from a file, etc.).
const payload = JSON.parse(fs.readFileSync("./payload.json"), "utf8");

// Validate the payload and get validation result.
const result = await JsonSchema.validate(luggageSchema, payload, JsonSchema.BASIC);
const isValid = result.valid;

If the payload is valid, isValid will return true with an empty list of error keywords. Otherwise isValid will return false with a list of error keywords.

Example Validation Message:


{
    keyword: 'https://schemas.amazon.com/selling-partners/definitions/product-types/meta-schema/v1#minUtf8ByteLength',
    absoluteKeywordLocation: 'https://schemas.amazon.com/selling-partners/definitions/product-types/schema/v1/LUGGAGE#/properties/contribution_sku/items/properties/value/minUtf8ByteLength',
    instanceLocation: '#/contribution_sku/0/value',
    valid: false
}

Keyword Validation

The Hyperjump - JSON Schema Core provides a framework that can be used to validate custom vocabulary, keywords, and other tools.

The following examples illustrate implementations of the JsonSchema that validate the custom vocabulary in instances of the Amazon Product Type Definition Meta-Schema.

MaxUniqueItemsKeyword script

const { Schema, Instance} = require("@hyperjump/json-schema-core");

const compile = (schema, ast, parentSchema) =>
{
    const maxUniqueItems = Schema.value(schema);
    // Retrieve the selectors defined in meta-schema
    const selectors = parentSchema.value.selectors;
    return [maxUniqueItems, selectors];
}

const interpret = ([maxUniqueItems, selectors], instance, ast) => {
    if (!Instance.typeOf(instance, "array")) {
        return false;
    }

    let uniqueItems = new Array();
    // For each instance in the example schema retrieve selectors combinations
    instance.value.forEach(inst => {
        let selectorCombination = {};
        Object.entries(inst).forEach(([key,value]) => {
            if(selectors != undefined && selectors.includes(key)) {
                selectorCombination[key] = value;
            }});
        uniqueItems.push(JSON.stringify(selectorCombination));
    });

    let countMap = new Map();
    // Add count of each unique selector combination in countMap
    uniqueItems.forEach(item => {
        countMap.get(item) != undefined ? countMap.set(item, countMap.get(item)+ 1): countMap.set(item, 1);
    });
    // Filter the countMap for values greater than maxUniqueItems
    let filteredItems = Array.from(countMap.entries()).filter(item => {
        return item[1] > maxUniqueItems;
    });
    // If filteredItems found then validation fails, else succeeds
    return filteredItems.length > 0 ? false : true;
};

module.exports = { compile, interpret };

MaxUtf8ByteLengthKeyword script

const { Schema, Instance} = require("@hyperjump/json-schema-core");

const compile = (schema, ast) => Schema.value(schema);

const interpret = (maxUtf8ByteLength, instance, ast) =>  Instance.typeOf(instance, "string") &&
    Buffer.byteLength(Instance.value(instance)) <= maxUtf8ByteLength;

module.exports = { compile, interpret };

MinUtf8ByteLengthKeyword script

const { Schema, Instance} = require("@hyperjump/json-schema-core");

const compile = (schema, ast) => Schema.value(schema);

const interpret = (minUtf8ByteLength, instance, ast) =>
    Instance.typeOf(instance, "string") && Buffer.byteLength(Instance.value(instance)) >= minUtf8ByteLength;

module.exports = { compile, interpret };

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