JSPM – hermesjs@0.1.1

Package Exports

hermesjs

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Readme

Hermes is a real-time messaging framework. It lets you connect a client with a broker and manage all the communication in between.

Installation

npm install --save hermesjs

Features

Express-like Routing and middlewares.
Forwarding messages from Client to Broker and viceversa.
Cancel the forwarding (message will continue passing through middlewares, if any).
Cancel the message (message will not continue passing through middlewares).
Answer back to client or broker, using same or different topic and payload.

Getting Started

Example: Simple router

app.use('hello/:name', (message, next) => {
  // Do whatever here...
  next();
});

Example: Using multiple route handlers

function checkIsHelloWorld (message, next) {
  // Message will not reach the other side if it's hello/world.
  // By calling next.cancel(), if the message comes from the client
  // it will not reach the broker and viceversa. However the message will
  // still be routed onto next middlewares, if any.
  if (message.route.params.name === 'world') return next.cancel();
}

app.use('hello/:name', checkIsHelloWorld, (message, next) => {
  console.log('You will see this even if it is hello/world. Read comments above.');
  next();
});

Example: Using routes only for messages from the broker

A message from broker, with hello/:name topic, is received:

app.in.broker.use('hello/:name', (message, next) => {
  console.log(`Broker sent 'hello/${message.route.params.name}'`);
  next(); // Forward message to client
});

Example: Using routes only for messages from the client

A message from client, with hello/:name topic, is received:

app.in.client.use('hello/:name', (message, next) => {
  console.log(`Client sent 'hello/${message.route.params.name}'`);
  next(); // Forward message to broker
});

Example: Cancelling messages

app.use('hello/:name', (message, next) => {
  // This will cancel the hello/world message. Even if we call
  // next, further middlewares will not be called.
  if (message.route.params.name === 'world') message.cancel();
  next();
});

Example: Replying back

A message from client, with hello/:name topic, is received:

app.in.client.use('hello/:name', (message, next) => {
  if (message.route.params.name === 'world') {
    return message.reply('hello/world/response', 'Stop using hello world, please.');
  }

  next();
});

A message saying Stop using hello world, please. is sent back to client, on hello/world/response topic. Note: When replying the message is automatically cancelled, so it will not reach further middlewares/routes.

Use Express-like router to organize your code

index.js

const hello = require('./routes/hello');

app.use('hello', hello);

routes/hello.js

const router = require('hermes').router();

router.use(':name', (message, next) => {
  console.log(`Hello ${message.route.params.name}!`);
  next();
});

router.use('world', (message, next) => {
  console.log(`Hello world!`);
  next();
});

router.in.client.use(':name', (message, next) => {
  message.reply('hello/response', { msg: `Hello ${message.route.params.name} from Hermes!` });
});

module.exports = router;

Use a global middleware

app.use((message, next) => {
  console.log('Handle message here...');
  next(); // Forward message
});

Catch errors

app.use((err, message, next) => {
  console.log('Handle error here...');
  next(err); // Optionally forward error to next middleware
});