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This module extends LoopBack with the ability to receive MessagePack requests and transparently convert it to a regular JavaScript object. It provides a BodyParser implementation and a component to register it.

Stability: ⚠️Experimental⚠️

Experimental packages provide early access to advanced or experimental functionality to get community feedback. Such modules are published to npm using 0.x.y versions. Their APIs and functionality may be subject to breaking changes in future releases.


npm i @loopback/rest-msgpack --save


The component should be loaded in the constructor of your custom Application class.

Start by importing the component class:

import {MsgPackBodyParserComponent} from '@loopback/rest-msgpack';

In the constructor, add the component to your application:


The body parser will accept requests with the following MIME type (Content-Type) blobs:

  • application/msgpack
  • application/x-msgpack
  • application/*+msgpack

Accepting MessagePack Requests

To accept MessagePack requests in a controller, amend the OpenAPI decorator to include the MIME type as a possible request body.

For example, to update the Todo controller to accept MessagePack:

import {post, getModelSchemaRef, requestBody} from '@loopback/rest';

class TodoController {
  // Omitted constructor for bevity

  async create(
      content: {
        // Change existing or append a new request body accepted MIME type
        'application/msgpack': {
          schema: getModelSchemaRef(Todo, {
            title: 'NewTodo',
            exclude: ['id'],
    todo: // Keep the request body object type, since the body parser transparently
    // converts it into a JavaScript object.
    Omit<Todo, 'id'>,

    // For bevity, the function does not return anything. See
    // 'Returning MessagePack Requests' below.
  ): void {

The MessagePack request payload will be transparently converted into a JavaScript object and validated against the JSON Schema.

Returning MessagePack Requests

To return MessagePack requests in a controller, amend the requestBody decorator to include the MIME type as a possible response and use a parser library.

For example, to update the Todo controller to return in MessagePack:

// `msgpack5` is re-exported by `@loopback/rest-msgpack` for convenience.
// It is recommended to bind it to context the inject it to benefit from
// dependency injection.
import {MsgPackBodyParserBindings, msgpack} from '@loopback/rest-msgpack';
import {inject} from '@loopback/core';
import {getModelSchemaRef, post, Response, RestBindings} from '@loopback/rest';

class TodoController {
  private readonly _response: Response;

    // Omitted other dependency injections (e.g. repository) for bevity.

    // Inject the Response object to the controller
    private readonly _res: Response,
  ) {}

  @get('/todos', {
    responses: {
      '200': {
        description: 'Array of Todo model instances',
        content: {
          // Update existing or amend new possible response
          'application/msgpack': {
            schema: {type: 'array', items: getModelSchemaRef(Todo)},
  async findTodos(
    filter?: Filter<Todo>,

    // Change function return type to Promise<void>.
  ): Promise<void> {
    // Internally, LoopBack 4 will try to guess and override the `Content-Type`
    // header, even after manually setting the headers.
    // Buffers are automatically detected as `application/octet-stream`.
    // We can use `Response.end()` to bypass that.
    // See:



Run npm test from the root folder.


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