Tips for Application Setup

Here are some tips for application setup to help avoid common pitfalls and mistakes.

Extend from RestApplication when using RestServer

If you want to use RestServer from the @loopback/rest package, we recommend extending RestApplication in your app instead of manually binding RestServer or RestComponent. RestApplication already uses RestComponent and makes useful functions in RestServer like handler() available at the app level. This means you can call the RestServer functions to perform all of your server-level setups in the app constructor without having to explicitly retrieve an instance of your server.

Serve static files

The RestServer allows static files to be served. It can be set up by calling the static() API.

app.static('/html', rootDirForHtml);

or

server.static(['/html', '/public'], rootDirForHtml);

Static assets are not allowed to be mounted on / to avoid performance penalty as / matches all paths and incurs file system access for each HTTP request.

The static() API delegates to serve-static to serve static files. Please see https://expressjs.com/en/starter/static-files.html and https://expressjs.com/en/4x/api.html#express.static for details.

{% include warning.html content="The static assets are served before LoopBack sequence of actions. If an error is thrown, the reject action will NOT be triggered." %}

Use unique bindings

Use binding names that are prefixed with a unique string that does not overlap with LoopBack's bindings. As an example, if your application is built for your employer FooCorp, you can prefix your bindings with fooCorp.

// This is unlikely to conflict with keys used by other component developers
// or within loopback itself!
app.bind('fooCorp.widgetServer.config').to(widgetServerConfig);

Avoid use of getSync

We provide the getSync function for scenarios where you cannot asynchronously retrieve your bindings, such as in constructor bodies.

However, the number of scenarios in which you must do this are limited, and you should avoid potential race conditions and retrieve your bindings asynchronously using the get function whenever possible.

Use caution with singleton binding scopes

By default, bindings for controllers will instantiate a new instance whenever they are injected or retrieved from their binding. Your application should only set singleton binding scopes on controllers when it makes sense to do so.