@morgan-stanley/composeui-messaging-client

This package provides a JavaScript/TypeScript client for connecting to the ComposeUI MessageRouter from web modules. It enables publish/subscribe messaging and service invocation between web applications and the ComposeUI messaging infrastructure.

Features

• Connect to the ComposeUI MessageRouter from browser or Electron environments
• Publish and subscribe to topics
• Register and invoke services
• Promise-based async API
• TypeScript typings included

Setup

Install the package:

npm install @morgan-stanley/composeui-messaging-client

Import and create a client:

import { createMessageRouter } from "@morgan-stanley/composeui-messaging-client";

let client = createMessageRouter();
await client.connect();

Usage

Subscribe to a topic

client.subscribe('exampleTopic', (message) => {
    const payload = JSON.parse(message.payload);
    console.log(payload);
});

Publish a message

await client.publish('exampleTopic', JSON.stringify({ foo: "bar" }));

Register a service

await client.registerService('myService', async (endpoint, payload, context) => {
    // handle the request and return a response string
    return "response";
});

Invoke a service

const response = await client.invoke('myService', "request payload");
console.log(response); // response string from the service

Unsubscribe from a topic

const subscription = client.subscribe('exampleTopic', handler);
// Later, to unsubscribe:
subscription.unsubscribe();

API Reference

createMessageRouter(options?)

Creates a new MessageRouter client instance.

• options (optional): Configuration object for the client.

client.connect() => Promise<void>

Establishes a connection to the MessageRouter.

• Returns: Promise<void>

client.close() => Promise<void>

Closes the connection to the MessageRouter.

• Returns: Promise<void>

client.subscribe(topic: string, subscriber: TopicSubscriber) => Promise<Unsubscribable>

Subscribes to a topic and registers a handler for incoming messages.

• topic: The topic string to subscribe to.
• handler: Function called with each message received: PartialObserver<TopicMessage> | ((message: TopicMessage) => void).
• Returns: Unsubscribable (call unsubscribe() to remove the handler)

client.publish(topic: string, payload: MessageBuffer, options?: PublishOptions) => Promise<void>

Publishes a message to a topic.

• topic: The topic string to publish to.
• payload: The message payload as a string.
• options: Additional publish options (correlationId).
• Returns: Promise<void>

client.invoke(service: string, payload: MessageBuffer, options?: InvokeOptions) => Promise<MessageBuffer | undefined>

Invokes a service and returns the response.

• service: The service name to invoke.
• payload: The request payload as a string.
• options: Additional invoke options (correlationId).
• Returns: Promise<string | undefined> (the response payload)

client.registerService(service: string, handler: MessageHandler, descriptor?: EndpointDescriptor | undefined) => Promise<void>)

Registers a service handler for a given service name.

• service: The service name to register.
• handler: Async function that receives the endpoint, request payload, and context, and returns a response payload. (endpoint: string, payload: MessageBuffer | undefined, context: MessageContext) => (MessageBuffer | Promise<MessageBuffer> | void | Promise<void>)
• descriptor: Additional description for the endpoint
• Returns: Promise<void>

client.unregisterService(service: string) => Promise<void>

Unregisters a previously registered service.

• service: The service name to unregister.
• Returns: Promise<void>

client.registerEndpoint(endpoint: string, handler: MessageHandler, descriptor?: EndpointDescriptor | undefined) => Promise<void>

Registers a local endpoint handler that is not advertised to other clients.

• endpoint: The endpoint name to register.
• handler: Async function that receives the endpoint, request payload, and context, and returns a response payload. (endpoint: string, payload: MessageBuffer | undefined, context: MessageContext) => (MessageBuffer | Promise<MessageBuffer> | void | Promise<void>).
• descriptor (optional): Endpoint descriptor object containing additional description for the endpoint.
• Returns: Promise<void>

client.unregisterEndpoint(endpoint: string) => Promise<void>

Unregisters a previously registered local endpoint.

• endpoint: The endpoint name to unregister.
• Returns: Promise<void>

client.state()

Returns the current connection state of the client.

• Type: ClientState (Created, Connecting, Connected, Closing, Closed)
• Usage example:

  if (client.state === ClientState.Connected) {
      // Client is connected
  }

© Morgan Stanley. See NOTICE file for additional information.