JSON Schema Validation Rules

Intermediate12 min

Enforce data integrity in MongoDB by defining JSON Schema validation rules that reject documents not matching your expected structure.

Prerequisites

-MongoDB 6+ with mongosh
-Understanding of JSON Schema basics

Steps

Create a collection with schema validation

Define a collection with JSON Schema rules that enforce required fields and types.

$ mongosh --eval 'db.createCollection("products", {validator: {$jsonSchema: {bsonType: "object", required: ["name", "price", "category"], properties: {name: {bsonType: "string", description: "must be a string"}, price: {bsonType: "number", minimum: 0, description: "must be a non-negative number"}, category: {enum: ["electronics", "clothing", "food", "books"], description: "must be a valid category"}, inStock: {bsonType: "bool"}}}}})' mydb

Test validation with a valid document

Insert a document that passes all validation rules.

$ mongosh --eval 'db.products.insertOne({name: "Laptop", price: 999.99, category: "electronics", inStock: true})' mydb

Test validation with an invalid document

Attempt to insert a document that violates the schema to verify enforcement.

$ mongosh --eval 'try { db.products.insertOne({name: "Bad Product", price: -10, category: "invalid"}); } catch(e) { print("Validation error: " + e.message); }' mydb

The insert will fail with a document validation error showing which rules were violated.

Add validation to an existing collection

Apply schema validation rules to a collection that already has data.

$ mongosh --eval 'db.runCommand({collMod: "orders", validator: {$jsonSchema: {bsonType: "object", required: ["customerId", "items", "total"], properties: {customerId: {bsonType: "string"}, items: {bsonType: "array", minItems: 1}, total: {bsonType: "number", minimum: 0}}}}, validationLevel: "moderate"})' mydb

validationLevel 'moderate' only validates inserts and updates to documents that already match the schema. Use 'strict' to validate all writes.

View current validation rules

Inspect the validation rules configured on a collection.

$ mongosh --eval 'db.getCollectionInfos({name: "products"})[0].options.validator' mydb

Full Script

full-script.sh

#!/bin/bash
# MongoDB Schema Validation Setup
set -euo pipefail

DB="mydb"

echo "=== Creating validated collection ==="
mongosh --quiet --eval "
db.createCollection('products', {
  validator: {
    $jsonSchema: {
      bsonType: 'object',
      required: ['name', 'price', 'category', 'sku'],
      properties: {
        name: {bsonType: 'string', minLength: 1, maxLength: 200},
        price: {bsonType: 'number', minimum: 0},
        category: {enum: ['electronics', 'clothing', 'food', 'books', 'other']},
        sku: {bsonType: 'string', pattern: '^[A-Z]{2,4}-[0-9]{4,8}$'},
        description: {bsonType: 'string', maxLength: 2000},
        tags: {bsonType: 'array', items: {bsonType: 'string'}},
        inStock: {bsonType: 'bool'}
      }
    }
  },
  validationLevel: 'strict',
  validationAction: 'error'
});
print('Collection created with validation');
" "$DB"

echo ""
echo "=== Testing valid insert ==="
mongosh --quiet --eval "
const result = db.products.insertOne({
  name: 'Wireless Mouse',
  price: 29.99,
  category: 'electronics',
  sku: 'ELEC-00142',
  tags: ['wireless', 'mouse', 'usb'],
  inStock: true
});
print('Inserted: ' + result.insertedId);
" "$DB"

echo ""
echo "=== Testing invalid inserts ==="
mongosh --quiet --eval "
const tests = [
  {doc: {name: 'Bad Price', price: -5, category: 'electronics', sku: 'ELEC-0001'}, reason: 'negative price'},
  {doc: {name: 'Bad Category', price: 10, category: 'invalid', sku: 'XX-0001'}, reason: 'invalid enum'},
  {doc: {price: 10, category: 'books', sku: 'BOOK-0001'}, reason: 'missing name'},
  {doc: {name: 'Bad SKU', price: 10, category: 'books', sku: 'bad-sku'}, reason: 'invalid SKU pattern'}
];
tests.forEach(t => {
  try {
    db.products.insertOne(t.doc);
    print('UNEXPECTED: ' + t.reason + ' - should have failed');
  } catch(e) {
    print('BLOCKED (' + t.reason + '): validation correctly rejected');
  }
});
" "$DB"

echo ""
echo "=== Current validation rules ==="
mongosh --quiet --eval "
const info = db.getCollectionInfos({name: 'products'})[0];
printjson(info.options);
" "$DB"

FAQ

Discussion

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#!/bin/bash # MongoDB Schema Validation Setup set -euo pipefail DB="mydb" echo "=== Creating validated collection ===" mongosh --quiet --eval " db.createCollection('products', { validator: { $jsonSchema: { bsonType: 'object', required: ['name', 'price', 'category', 'sku'], properties: { name: {bsonType: 'string', minLength: 1, maxLength: 200}, price: {bsonType: 'number', minimum: 0}, category: {enum: ['electronics', 'clothing', 'food', 'books', 'other']}, sku: {bsonType: 'string', pattern: '^[A-Z]{2,4}-[0-9]{4,8}$'}, description: {bsonType: 'string', maxLength: 2000}, tags: {bsonType: 'array', items: {bsonType: 'string'}}, inStock: {bsonType: 'bool'} } } }, validationLevel: 'strict', validationAction: 'error' }); print('Collection created with validation'); " "$DB" echo "" echo "=== Testing valid insert ===" mongosh --quiet --eval " const result = db.products.insertOne({ name: 'Wireless Mouse', price: 29.99, category: 'electronics', sku: 'ELEC-00142', tags: ['wireless', 'mouse', 'usb'], inStock: true }); print('Inserted: ' + result.insertedId); " "$DB" echo "" echo "=== Testing invalid inserts ===" mongosh --quiet --eval " const tests = [ {doc: {name: 'Bad Price', price: -5, category: 'electronics', sku: 'ELEC-0001'}, reason: 'negative price'}, {doc: {name: 'Bad Category', price: 10, category: 'invalid', sku: 'XX-0001'}, reason: 'invalid enum'}, {doc: {price: 10, category: 'books', sku: 'BOOK-0001'}, reason: 'missing name'}, {doc: {name: 'Bad SKU', price: 10, category: 'books', sku: 'bad-sku'}, reason: 'invalid SKU pattern'} ]; tests.forEach(t => { try { db.products.insertOne(t.doc); print('UNEXPECTED: ' + t.reason + ' - should have failed'); } catch(e) { print('BLOCKED (' + t.reason + '): validation correctly rejected'); } }); " "$DB" echo "" echo "=== Current validation rules ===" mongosh --quiet --eval " const info = db.getCollectionInfos({name: 'products'})[0]; printjson(info.options); " "$DB"