json-rpc-engine

What is json-rpc-engine?

The json-rpc-engine npm package is a JavaScript library that provides a framework for building JSON-RPC 2.0 servers and clients. It allows you to create middleware stacks to handle JSON-RPC requests and responses, making it easier to manage and extend your JSON-RPC services.

What are json-rpc-engine's main functionalities?

Creating a JSON-RPC Engine

This feature allows you to create a new JSON-RPC engine instance, which serves as the core component for handling JSON-RPC requests and responses.

const { JsonRpcEngine } = require('json-rpc-engine');
const engine = new JsonRpcEngine();

Adding Middleware

You can add middleware to the JSON-RPC engine to handle specific methods or perform actions before passing the request to the next middleware. In this example, a middleware is added to handle the 'hello' method.

engine.push((req, res, next, end) => {
  if (req.method === 'hello') {
    res.result = 'world';
    return end();
  }
  next();
});

Handling Requests

This feature demonstrates how to handle a JSON-RPC request using the engine. The request is processed through the middleware stack, and the response is returned via a callback function.

const request = { jsonrpc: '2.0', method: 'hello', id: 1 };
engine.handle(request, (err, res) => {
  if (err) {
    console.error(err);
  } else {
    console.log(res);
  }
});

Other packages similar to json-rpc-engine

jayson

Jayson is a full-featured JSON-RPC 2.0/1.0 server and client for Node.js. It provides a more comprehensive set of features for building JSON-RPC services, including support for both HTTP and TCP transports, batch requests, and more. Compared to json-rpc-engine, Jayson offers a more extensive set of tools for different transport layers and use cases.

jsonrpc-lite

Jsonrpc-lite is a lightweight JSON-RPC 2.0 library for Node.js. It focuses on providing a simple and minimalistic approach to handling JSON-RPC requests and responses. While json-rpc-engine provides a middleware-based architecture, jsonrpc-lite is more straightforward and easier to use for basic JSON-RPC implementations.

node-json-rpc

Node-json-rpc is another JSON-RPC 2.0 server and client library for Node.js. It offers a simple API for creating JSON-RPC servers and clients, with support for both HTTP and WebSocket transports. Compared to json-rpc-engine, node-json-rpc provides a more traditional approach to building JSON-RPC services without the middleware stack.

README

RpcEngine

a tool for processing JSON RPC

usage

const RpcEngine = require('json-rpc-engine')

let engine = new RpcEngine()

Build a stack of json rpc processors by pushing in RpcEngine middleware.

engine.push(function(req, res, next, end){
  res.result = 42
  end()
})

JSON RPC are handled asynchronously, stepping down the stack until complete.

let request = { id: 1, jsonrpc: '2.0', method: 'hello' }

engine.handle(request, function(err, res){
  // do something with res.result
})

RpcEngine middleware has direct access to the request and response objects. It can let processing continue down the stack with next() or complete the request with end().

engine.push(function(req, res, next, end){
  if (req.skipCache) return next()
  res.result = getResultFromCache(req)
  end()
})

By passing a 'return handler' to the next function, you can get a peek at the result before it returns.

engine.push(function(req, res, next, end){
  next(function(cb){
    insertIntoCache(res, cb)
  })
})

RpcEngines can be nested by converting them to middleware asMiddleware(engine)

const asMiddleware = require('json-rpc-engine/lib/asMiddleware')

let engine = new RpcEngine()
let subengine = new RpcEngine()
engine.push(asMiddleware(subengine))

gotchas

Handle errors via end(err), NOT next(err).

/* INCORRECT */
engine.push(function(req, res, next, end){
  next(new Error())
})

/* CORRECT */
engine.push(function(req, res, next, end){
  end(new Error())
})