ASP.NET WEB API Napredne tehnike i mogućnosti RENATO JOVIĆ, Tagit Adriatica d.o.o.

Agenda ASP.NET WebAPI pipeline overview Message Handlers (DelegatingHandler) Filters (ActionFilterAttribute) Formatters (MediaTypeFormatter) Exception Handling ExceptionLogger ExceptionHandler Caching Streaming (upload & download) What’s new in Web API 2

ASP.NET Web API is a framework that makes it easy to build HTTP services that reach a broad range of clients, including browsers and mobile devices. It is an ideal platform for building RESTful applications on the.NET Framework ASP.NET WebAPI

ASP.NET WebAPI pipeline Host Message Handlers Controller Model Binding Result conversion Action Method

Journey of HTTP message

MESSAGE HANDLERS

HTTP message handlers are the first stage in the processing pipeline. They process HTTP request messages on the way in, and HTTP response messages on the way out. Derive from DelegatingHandler Global or per-route handlers Message Handlers

Delegating handler #1 Delegating handler #2 HttpRouting Dispatcher HttpController Dispatcher Host Controller

MESSAGE HANDLERS Demo

FILTERS

Filters are great way to add extra functionality to your Web API service or to secure your controllers and actions. WebAPI filters != MVC filters Filters

Authentication filter Authorization filter Action filters Controller Action Method Model Binding Result conversion Result conversion – out of the box formatters for JSON/XML/BSON (v2) Ability to easy write your own custom formatters (results) – CSV, vCard …

FILTERS & FORMATTERS Demo

ERROR HANDLING

Client error – HTTP 4xx Server error – HTTP 5xx Avoid try/catch in controller actions Error handling

ExceptionHandler Handler for catching exception in pipeline One handler at the time ExceptionLogger Handler for logging the exceptions Multiple handlers at the time IMPORTANT : Doesn’t catch exception caused by: Serialization errors, controller initialization, pre/post controller

EXCEPTION HANDLING Demo

HTTP CACHING

Http caching - client Cache-Control no-cache (default) no-store max-age (TTL, seconds) Private (no store at proxies) Expires Default value (-1) Date of expiration – UTC – Can be year from now – max-age from Cache- Control have advantage

Http caching - server WebAPI doesn’t support OutputCache MVC filter Two possibilities – Manually adding caching header to response (Etag value) – Use third party stuff (CacheCow, OutputCache…)

Http caching - ETag Response header name – Etag Request header name – If-None-Match Client sends Etag inside request headers Server compare received Etag with resource Etag value RESPONSE – HTTP 304 (Not modified) Server returns updated resource with new Etag Client caches response == !=

HTTP CACHING Demo

HTTP STREAMING

Chunked transfer - download System.Net.Http.StreamCont ent Pull data direct from the file Avoids creating local byte array data to hold the file System.Net.Http.PushStreamCon tent Size is not known Use stream Flush() to send chunk of data to the client

Chunked transfer - upload System.Net.Http.HttpContent.ReadAsStreamAsync System.Net.Http.HttpContent.ReadAsStreamMultipartA sync Non-browser file upload Stream data direct to the file on the server Browser file upload (form data)

HTTP STREAMING Demo

What’s new in WebAPI 2 Out of the box support for BSON using JSON.NET library Attribute routing (Route and RoutePrefix) Odata improvements CORS (Cross Origin Request Sharing) New IHttpResult response – return Ok(); – return NotFound(…);

@rjovic

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