json-rpc-protocol

JSON-RPC 2 protocol messages parsing and formatting

Install

Installation of the npm package:

> npm install --save json-rpc-protocol

Usage

Errors

// ES5
var protocol = require('json-rpc-protocol')

var JsonRpcError = protocol.JsonRpcError
var InvalidJson = protocol.InvalidJson
var InvalidRequest = protocol.InvalidRequest
var MethodNotFound = protocol.MethodNotFound
var InvalidParameters = protocol.InvalidParameters

// ES6
import {
  JsonRpcError,
  InvalidJson,
  InvalidRequest,
  MethodNotFound,
  InvalidParameters
} from 'json-rpc-protocol'

This is the base error for all JSON-RPC errors:

throw new JsonRpcError(message, code)

The JSON-RPC 2 specification defined also the following specialized errors:

// Parse error: invalid JSON was received by the peer.
throw new InvalidJson()

// Invalid request: the JSON sent is not a valid JSON-RPC 2 message.
throw new InvalidRequest()

// Method not found: the method does not exist or is not available.
throw new MethodNotFound(methodName)

// Invalid parameters.
throw new InvalidParameters(data)

Custom errors can of course be created, they just have to inherit JsonRpcError:

// ES5
function MyError () {
  JsonRpcError.call(this, 'my error', 1)
}
MyError.prototype = Object.create(JsonRpcError.prototype, {
  constructor: {
    value: MyError
  }
})

// ES6
class MyError extends JsonRpcError {
  constructor () {
    super('my error', 1)
  }
}

Parsing

// ES5
var parse = require('json-rpc-protocol').parse

// ES6
import {parse} from 'json-rpc-protocol'

The parse() function parses, normalizes and validates JSON-RPC 1 or JSON-RPC 2 messages.

These message can be either JS objects or JSON strings (they will be parsed automatically).

This function may throws:

• InvalidJson: if the string cannot be parsed as a JSON;
• InvalidRequest: if the message is not a valid JSON-RPC message.

parse('{"jsonrpc":"2.0", "method": "foo", "params": ["bar"]}')
// → {
//   [type: 'notification']
//   jsonrpc: '2.0',
//   method: 'foo',
//   params: ['bar']
// }

parse('{"jsonrpc":"2.0", "id": 0, "method": "add", "params": [1, 2]}')
// → {
//   [type: 'request']
//   jsonrpc: '2.0',
//   id: 0,
//   method: 'add',
//   params: [1, 2]
// }

parse('{"jsonrpc":"2.0", "id": 0, "result": 3}')
// → {
//   [type: 'response']
//   jsonrpc: '2.0',
//   id: 0,
//   result: 3
// }

A parsed message has a non enumerable property type set to easily differentiate between types of JSON-RPC messages.

Response/Error

The parse.result helper parses and returns the result of a response message or throws the error of an error message:

try {
  const result = await parse.result(message)
  // do something with the result
} catch (error) {
  // deal with the failure
}

Formatting

// ES5
var format = require('json-rpc-protocol').format

// ES6
import {format} from 'json-rpc-protocol'

The format.*() functions can be used to create valid JSON-RPC messages (as JavaScript strings).

Notification

format.notification('foo', ['bars'])
// → {
//   "jsonrpc": "2.0",
//   "method": "foo",
//   "params": ["bar"]
// }

The last argument, the parameters of the notification, is optional and defaults to undefined.

Request

The last argument, the parameters of the request, is optional and defaults to undefined.

format.request(0, 'add', [1, 2])
// → {
//   "jsonrpc": "2.0",
//   "id": 0,
//   "method": "add",
//   "params": [1, 2]
// }

Response

A successful response:

format.response(0, 3)
// → {
//   "jsonrpc": "2.0",
//   "id": 0,
//   "result": 3
// }

A failed response:

var MethodNotFound = require('json-rpc-protocol').MethodNotFound

format.error(0, new MethodNotFound('add'))
// → {
//   "jsonrpc": "2.0",
//   "id": 0,
//   "error": {
//     "code": -3601,
//     "message": "method not found: add",
//     "data": "add"
//   }
// }

Note: the error to format must implement a toJsonRpcError function which returns an object or it will be automatically replaced by an unknown error for security reasons.

toJsonRpcError example:

toJsonRpcError () {
  return {
    code: 42, // must be an integer
    message: 'Hacking too much time!', // must be a string
    data: [ 'Hackerman' ] // optional
  }
}

Development

# Install dependencies
> npm install

# Run the tests
> npm test

# Continuously compile
> npm run dev

# Continuously run the tests
> npm run dev-test

# Build for production (automatically called by npm install)
> npm run build

Related

• json-rpc-peer − High level interface

Contributions

Contributions are very welcomed, either on the documentation or on the code.

You may:

• report any issue you've encountered;
• fork and create a pull request.

License

ISC © Julien Fontanet