What's a handler?

In Pomona a handler class is where an application defines how a HTTP request will be handled. This is what would be called a "controller" in many other web frameworks.

We'll typically define one handler class per resource type. This can be done by either using the HandledBy<T>(..) method of the fluent configuration API, or by overriding the GetResourceHandlers convention.

Methods in the handler class are duck-typed, and resolved using their name and signature.

A handler is instantiated using the IoC container associated with the processed NancyContext.

When desired, multiple handler classes for can be defined for a resource type. For example one class per HTTP action.

Types of handler methods

Query handlers

The Query handlers are used for GET requests to resource collections. They are required to return an IQueryable<T>.

They must follow the naming pattern Get{Resources} or Query{Resources}, where {Resources} must be the plural name of the resource type. Or, if the handler class is only used for one type, it can simply be called Query.

    public class GameConsoleHandler
    {
        public IQueryable<GameConsole> Query()
        {
            return
                new[]
                {
                    new GameConsole() { Id = "a2600", Name = "Atari 2600" },
                    new GameConsole() { Id = "gameboy", Name = "Game Boy" },
                    new GameConsole() { Id = "nes", Name = "Nintendo Entertainment System" },
                }.AsQueryable();
        }
    }

Here a GET request to /game-consoles would be routed to the Query() method of the handler type.

Get single resource by id

A method named Get{Resource} or Get that takes the id as its first argument and returns a resource of the correct type will handle GET requests for resources by id.

Note that by default this method is implemented by using the query handler, so in many cases manually implementing this method is redundant.

        public Customer GetCustomer(int id)
        {
            return this.customerRepo.GetById(id);
        }

Post resource

A method named Post or Post{Resource} taking the deserialized resource as a parameter will be used for handling POST requests .

        public Customer Post(Customer customer)
        {
            this.customerRepo.Save(customer);
            return customer;
        }

Patch resource

A method named Patch or Patch{Resource} receives the fully patched resource on a PATCH.

        public Customer Patch(Customer customer)
        {
            this.customerRepo.Save(customer);
            return customer;
        }

Pomona uses a custom JSON patch format, more details can be found in Using exposed service

Delete resource

A method named Delete or Delete{Resource} that either takes a resource or id parameter will be used for DELETE requests.

        public void Delete(Customer customer)
        {
            this.customerRepo.Delete(customer);
        }