MongoJSON

MongoJSON provides parse and stringify functions with support for MongoDB data types. It allows you to serialize MongoDB filters and documents as JSON strings while preserving type information.

An in Depth Example

This guide also has an in depth example of a working application built with EventFabric. Combining DDD, CQRS and Event Sourcing.

Check out the In Depth Example page to learn how everything is connected and works out in a real-world application.

Basic Usage

import { MongoJSON } from "@nimbus-cqrs/mongodb";

// Parse a JSON string with MongoDB type prefixes
const filter = MongoJSON.parse('{"_id": "objectId::507f1f77bcf86cd799439011"}');
// Result: { _id: ObjectId("507f1f77bcf86cd799439011") }

// Stringify an object to JSON
const json = MongoJSON.stringify({ name: "John", age: 30 });
// Result: '{"name":"John","age":30}'

Type Prefixes

The parse function recognizes special prefixes to convert strings to MongoDB types:

Prefix	Converts To	Example
objectId::	ObjectId	"objectId::507f1f77bcf86cd799439011"
date::	Date	"date::2024-01-15T10:30:00Z"
int::	number	"int::42"
double::	number	"double::19.99"

Parse Examples

import { MongoJSON } from "@nimbus-cqrs/mongodb";

// ObjectId conversion
const idFilter = MongoJSON.parse(
    '{"_id": "objectId::507f1f77bcf86cd799439011"}'
);
// { _id: ObjectId("507f1f77bcf86cd799439011") }

// Date conversion
const dateFilter = MongoJSON.parse(
    '{"createdAt": {"$gte": "date::2024-01-01T00:00:00Z"}}'
);
// { createdAt: { $gte: Date("2024-01-01T00:00:00Z") } }

// Integer conversion
const countFilter = MongoJSON.parse('{"count": {"$gt": "int::100"}}');
// { count: { $gt: 100 } }

// Multiple types
const complexFilter = MongoJSON.parse(`{
    "_id": "objectId::507f1f77bcf86cd799439011",
    "price": {"$lte": "double::49.99"},
    "createdAt": {"$gte": "date::2024-01-01T00:00:00Z"},
    "quantity": {"$gt": "int::0"}
}`);

Operator Blacklist

For security, MongoJSON.parse blocks certain MongoDB operators by default:

// This will throw an error
MongoJSON.parse('{"$where": "this.name === \\"admin\\""}');
// Error: Operator '$where' is not allowed

// Custom blacklist
MongoJSON.parse(jsonString, ["$where", "$expr"]);

The default blacklist includes $where to prevent code injection attacks.

Use Case: API Filters

MongoJSON is useful when accepting MongoDB filters from API requests:

import { MongoJSON } from "@nimbus-cqrs/mongodb";

app.get("/users", async (c) => {
    const filterParam = c.req.query("filter");

    // Parse the filter from query string
    const filter = filterParam ? MongoJSON.parse(filterParam) : {};

    const users = await userRepository.find({ filter });
    return c.json(users);
});

// Example request:
// GET /users?filter={"status":"active","createdAt":{"$gte":"date::2024-01-01T00:00:00Z"}}

Error Handling

MongoJSON.parse throws an InvalidInputException for:

• Invalid JSON syntax
• Blacklisted operators

import { MongoJSON } from "@nimbus-cqrs/mongodb";

try {
    const filter = MongoJSON.parse('{"invalid json}');
} catch (error) {
    // InvalidInputException with JSON parse error details
}

try {
    const filter = MongoJSON.parse('{"$where": "1===1"}');
} catch (error) {
    // Error: Operator '$where' is not allowed
}