Angel is inspired by Express, and such, request handlers in general resemble those from Express. Request handlers can return any Dart object (see how they are handled). Basic request handlers accept two parameters:
RequestContext - Contains vital information about the client requesting a resource, such as request method, request body, IP address, etc. The request object can also be used to pass information from one handler to the next.
ResponseContext - Allows you to send headers, write data, and more, to be sent to the client. To prevent a response from being modified by future handlers, call res.end() to prevent further writing.
Request handlers can return any Dart value. Return values are handled as follows:
If you return a bool: Request handling will end prematurely if you return false, but it will continue if you return true.
If you return null: Request handling will continue, unless you closed the response object by calling res.close(). Some response methods, such as res.redirect() or res.serialize() automatically close the response.
A RequestHandler: the returned handler will be executed.
A Stream: toList will be called, and then returned.
A Future: it will be awaited, and then returned.
Anything else: Whatever other Dart value you return will be serialized as a response. The default method is to encode responses as JSON, using json.encode. However, you can change a response's serialization method by setting res.serializer = foo;. If you want to assign the same serializer to all responses, globally set serializer on your Angel instance. If you are only returning JSON-compatible Dart objects, like Maps or Lists, you might consider injecting JSON.encode as a serializer, to improve runtime performance (this is the default in 2.0).