JSON-RPC MSG

Zero-dependencies library for Node.js and JavaScript to parse and create JSON RPC 2.0 messages.

About

The json-rpc-msg is a library with zero dependencies that provides an API to parse and create valid JSON-RPC 2.0 messages.

Quick start

Install:

npm install --save json-rpc-msg 

Usage:

const JsonRPC = require('json-rpc-msg');

function sendMessageToClient(message) {
    // Some code that sends passed message to clients, e.g. over HTTP or websocket
}

/*--------------------------------------
 | Create JSON-RPC request
 |--------------------------------------
 |*/
const requestObj = JsonRPC.createRequest(123, 'updateUser', {id: 1, name: 'Alex'});
sendMessageToClient(requestObj);
// {
//   jsonrpc: '2.0',
//   id: 123,
//   method: 'updateUser',
//   params: {id: 1, name: 'Alex'}
// }

/*--------------------------------------
 | Parse JSON-RPC message 
 |--------------------------------------
 |*/
try {
    // Valid message:
    const message = JsonRPC.parseMessage('{"jsonrpc": "2.0", "id": 123, "method": "update", "params": [1,2,3]}');
    // {
    //     type: 'request',
    //     payload: {
    //         id: 123,
    //         method: 'update',
    //         params: [1,2,3]
    //     }
    // }
    
    
    // Invalid message (ParserError will be thrown):
    const failedMessage = JsonRPC.parseMessage('not valid JSON RPC message');
}
catch(e) {
    // If parser failed to parse message - send error to client:
    if (e instanceof JsonRPC.ParserError) {
        sendMessageToClient(e.rpcError);
    }
    // Otherwise throw error up:
    else {
        throw e;
    }
}

API Reference

Constants

ERRORS

Contains list of JSON-RPC error codes. Map with the following structure:

JsonRPC.ERRORS = {
    SOME_ERROR: {
        code: 123,
        message: 'Some message for error'
    }
}

Can be used to manually create response with JSON-RPC error:

// Create "Method not found" error for received request with ID=123
const errorObj = JsonRPC.createError(123, JsonRPC.ERRORS.METHOD_NOT_FOUND);
// {
//   jsonrpc: '2.0',
//   id: 123,
//   error: {
//     code: -32601,
//     message: 'Method not found'
//   }
// }

Some particular implementations of JSON-RPC protocol may want to add additional custom errors to this object (note that errors from -32768 to 32000 are reserved for future use, for more information see specification to error object in JSON-RPC v2.0):

JsonRPC.ERRORS.NEW_ERROR_FOR_SOME_IMPLEMENTATION = {
    code: -32000,
    message: 'Message of added error'
}
const message = JsonRPC.createError(123, JsonRPC.ERRORS.NEW_ERROR_FOR_SOME_IMPLEMENTATION);
// {
//   jsonrpc: '2.0',
//   id: 123,
//   error: {
//     code: -32000,
//     message: 'Message of added error'
//   }
// }

MESSAGE_TYPES

Contains list of supported message types.

• REQUEST - message with "id" and "method" props (and optional "params")
• INTERNAL_REQUEST - the same as REQUEST, but only if "method" starts with "rpc.". This type of request is only for rpc-internal methods and extensions.
• NOTIFICATION - message without "id", and with "method" prop (and optional "params")
• INTERNAL_NOTIFICATION - the same as NOTIFICATION, but only if "method" starts with "rpc.". This type of notification is only for rpc-internal notifications and extensions.
• RESPONSE - message with "id" and "result" props. Represents response from server.
• ERROR - message with "id" and "error" props. Represents response from server with error.
• BATCH - message that is a group of JSON-RPC messages (array).

This constant should be mainly used to check type of parsed message:

const receivedJSON = '{"jsonrpc": "2.0", "id": 1, "method": "log", "params": ["Some string to log"]}';
const message = JsonRPC.parseMessage(receivedJSON);
switch (message.type) {
    case JsonRPC.MESSAGE_TYPES.REQUEST:
        // Do something with request
        break;
    case JsonRPC.MESSAGE_TYPES.NOTIFICATION:
        // Do something with notification
        break;
    // ...etc
}

INTERNAL_MESSAGE_PREFIX

Contains string ("rpc."), that should be added to start of any message/notification that is intended for internal usage of some particular JSON-RPC implementation. e.g:

// Creates notification with name "rpc.someNotification":
const notificationJson = JsonRPC.createInternalNotification(`${JsonRPC.INTERNAL_MESSAGE_PREFIX}someNotification`);

// Because "createInternalNotification" adds this prefix automatically - the following code will
// produce the same result:
const notificationJson2 = JsonRPC.createInternalNotification('someNotification');

console.log(notificationJson === notificationJson2); // => true

Methods

createRequest(id, method [,params])

Creates JSON-RPC request

NOTE: If method name starts with "rpc." error will be thrown. To create requests for "rpc." methods use createInternalRequest function instead.

• id {string|number}: request ID
• method {string}: method name to call
• params {Object|Array} (optional): parameters to pass in method

const requestObj = JsonRPC.createRequest(123, 'refreshAllUsers')
// {
//   jsonrpc: '2.0',
//   id: 123,
//   method: 'refreshAllUsers',
// }

const requestObj = JsonRPC.createRequest(123, 'updateUser', {id: 1, name: 'Alex'})
// {
//   jsonrpc: '2.0',
//   id: 123,
//   method: 'updateUser',
//   params: {id: 1, name: 'Alex'}
// }

createNotification(method, [,params])

Creates JSON-RPC notification

NOTE: If notification name starts with "rpc." error will be thrown. To create requests for "rpc." notifications use createInternalNotification function instead.

• method {string}: method name to call
• params {Object|Array} (optional): parameters to pass in method

const notificationObj = JsonRPC.createNotification('allUsersWereRefreshed')
// {
//   jsonrpc: '2.0',
//   method: 'allUsersWereRefreshed'
// }

const notificationObj = JsonRPC.createNotification('userUpdated', {id: 1, name: 'Alex'})
// {
//   jsonrpc: '2.0',
//   method: 'userUpdated',
//   params: {id: 1, name: 'Alex'}
// }

createResponse(id, result)

Creates successfull JSON-RPC response to some request

• id {string|number}: request ID
• result {Mixed}: response data

const responseObj = JsonRPC.createResponse(123, {id: 1, name: 'Alex', age: 23})
// {
//   jsonrpc: '2.0',
//   id: 123,
//   response: {id: 1, name: 'Alex', age: 23}
// }

const responseObj = JsonRPC.createResponse(123, null)
// {
//   jsonrpc: '2.0',
//   id: 123,
//   response: null 
// }

createError(id, error, [, additionalErrorData])

Creates JSON-RPC response with error

• id {string|number}: request ID
• error {number|{code: number, message: string?}}: error code (number) or object with "code" and optional "message" property
• additionalErrorData {Object|Array}: additional data for error

// All of the following statements will produce same result:
const errorResponseObj = JsonRPC.createError(123, -32602);
const errorResponseObj = JsonRPC.createError(123, JsonRPC.ERRORS.INVALID_PARAMS);
const errorResponseObj = JsonRPC.createError(123, {code: -32602});
const errorResponseObj = JsonRPC.createError(123, {code: -32602, message: 'Invalid params'});
// {
//   jsonrpc: '2.0',
//   id: 123,
//   error: {
//     code: -32602,
//     message: 'Invalid params'
//   }
// }

There is ability to provide additional information for error, passing additionalParams argument, e.g. if invalid user name and age where passed in request:

const errorResponseObj = JsonRPC.createError(123, JsonRPC.ERRORS.INVALID_PARAMS, {
    name: "User name can't be less then 6 characters",
    age: "User age is not defined"
});
// {
//   jsonrpc: '2.0',
//   id: 123,
//   error: {
//     code: -32602,
//     message: 'Invalid params',
//     data: {
//         name: 'User name can't be less then 6 characters',
//         age: 'User age is not defined'
//     }
//   }
// }

If error passed as object with property "code" but without property "message" this method will look at JsonRPC.ERRORS to find error with given code, and find appropriate message. If there is no error with given code in ERRORS - message will be defaulted to "Internal Server Error":

JsonRPC.ERRORS.NEW_ERROR = {
    code: 666,
    message: 'Number of the Beast'
}

// Message will be taken from ERRORS object:
const errorResponseObj = JsonRPC.createError(123, {code: 666});
// {
//   jsonrpc: '2.0',
//   id: 123,
//   error: {
//     code: 666,
//     message: 'Number of the Beast'
// }

// Message in ERRORS object will not be used because "message" is provided:
const errorResponseObj = JsonRPC.createError(123, {code: 666, message: 'replaced message'});
// {
//   jsonrpc: '2.0',
//   id: 123,
//   error: {
//     code: 666,
//     message: 'replaced message'
// }

// Error that is not in ERRORS object will have default "Internal Serve Error" message:
const errorResponseObj = JsonRPC.createError(123, {code: 999});
// {
//   jsonrpc: '2.0',
//   id: 123,
//   error: {
//     code: 999,
//     message: 'Internal Server Error'
// }

parseMessage(message)

Validates and parses given JSON-RPC message

• message {string|Object|array} - JSON string or message object or batch of messages (array)

Returns object with properties "type" and "payload". Type can be one of the types listed in JsonRPC.MESSAGE_TYPES constant. Payload will contain message body, which depends on message type:

• REQUEST and INTERNAL_REQUEST will contain "id", "method" and optional "params" properties:

  const message = JsonRPC.parseMessage('{"jsonrpc": "2.0", "id": 123, "method": "update", "params": [1,2,3]}');
  // {
  //     type: 'request',
  //     payload: {
  //         id: 123,
  //         method: 'update',
  //         params: [1,2,3]
  //     }
  // }

• NOTIFICATION and INTERNAL_NOTIFICATION will contain "method" and optional "params" properties:

  const message = JsonRPC.parseMessage('{"jsonrpc": "2.0", "method": "updated", "params": [1,2,3]}');
  // {
  //     type: 'notification',
  //     payload: {
  //         method: 'updated',
  //         params: [1,2,3]
  //     }
  // }

• RESPONSE will contain "id" and "result" properties:

  const message = JsonRPC.parseMessage('{"jsonrpc": "2.0", "id": 1, "result": [1,2,3]}');
  // {
  //     type: 'response',
  //     payload: {
  //         id: 1,
  //         result: [1,2,3]
  //     }
  // }

• ERROR will contain "id" and "error" properties:

  const message = JsonRPC.parseMessage('{"jsonrpc": "2.0", "id": 1, "error": {"code": -32602, "message": "Invalid params", "data": [1,2,3]}}');
  // {
  //     type: 'error',
  //     payload: {
  //         id: 1,
  //         error: {
  //             code: -32602,
  //             message: 'Invalid params',
  //             data: [1,2,3] 
  //         }
  //     }
  // }

• BATCH will contain array of parsed messages in "payload" property. If some of this messages failed to be parsed - there will be an error in this array instead of parsed message:

  const message = JsonRPC.parseMessage('['+
      '{"jsonrpc": "2.0", "id": 1, "result": "OK"}' +
      '{"jsonrpc": "2.0", "id": 1, "error": {"code": -32602, "message": "Invalid params", "data": [1,2,3]}}]' +
      'invalid JSON-RPC message' +
  ']');
  // {
  //   type: 'batch',
  //   payload: [
  //     {
  //       type: 'response',
  //       payload: {
  //         id: 1,
  //           result: [1,2,3]
  //       }
  //     },
  //     {
  //       type: 'error',
  //       payload: {
  //         id: 1,
  //         error: {
  //           code: -32602,
  //           message: 'Invalid params',
  //           data: [1,2,3] 
  //         }
  //       },
  //     },
  //     [ParserError Object]
  //   ] 
  // }

createInternalRequest

The same as createRequest, but allows to create requests with method name that starts with "rpc." prefix. If this prefix is not presented in method name it will be added automatically.

createInternalNotification

The same as createNotification, but allows to create notification with name that starts with "rpc." prefix. If this prefix is not presented in name it will be added automatically.

License

MIT