Handler

Handler is the core concept in Spry, but it is not unique to Spry. Because HttpServer in dart:io also handles requests through FutureOr<dynamic> Function(HttpRequest).

The Handler in Spry only encapsulates its specific structure. In most cases, you do not need to implement the Handler interface or use it unless you deeply customize Spry.

Handler interface

The Handler interface has a T type parameter and a handle method. T represents the return value type of the handle method.

class MyHandler implements Handler<String> {
    @override
    T handle(HttpRequest request) {
        return 'Hello, World!';
    }
}

Or use an async method:

class MyHandler implements Handler<String> {
    @override
    Future<T> handle(HttpRequest request) async {
        return 'Hello, World!';
    }
}

The type of handle is FutureOr<T> Function(HttpRequest), which is consistent with the requirements in dart:io.

Closure Handler

Closure Handler is the most common handler when registering routes, and it is also the recommended method. Usually, you can directly pass in a Closure that conforms to the FutureOr<T> Function(HttpRequest) type when registering a route.

router.get('/hello', (request) async {
    return 'Hello, World!';
});

You can use a ClosureHandler to wrap a Closure when you definitely think a Handler is needed somewhere else.

final handler = ClosureHandler((request) async {
    return 'Hello, World!';
});

app.get('/hello', handler.handle);

Although this may seem redundant, it makes it easier to use Handler when needed. For example, if you expect to register a route via app.routes.addRoute, then you need a Handler.

final handler = ClosureHandler((request) async {
    return 'Hello, World!';
});
final route = Route(method: "GET", segments: '/hello'.asSegements, handler: handler);

app.routes.addRoute(route);

These functions are reserved for users who perform in-depth customization based on Spry. Generally, you do not need to use them.