Codemotion Rome 2014

WEB API 2.X

What’s new and …..

Ugo LattanziHead of Technologies @ Gaia

Microsoft MVP, MCP

Twitter: @imperugo

Blog (en): http://tostring.it

Blog (it): http://imperugo.tostring.it

E-mail: imperugo@gmail.com

Agenda• Who am I?• What’s ASP.NET Web API?• What’s a RESTful service?;• Routing old and new;• Global Error Handling;• Help Page;• CORS;• BSON serialization;• Ignore route;• …. caching;

WHO AM I?

Who am I?• Head of Technologies at Gaia (www.gaia.is.it);• Microsoft MVP (ASP.NET / IIS);• Speaker / Trainer;• Book / Article author;• “Opensourcer”;• Github lover;• Everything about Web Dev;

What’s ASP.NET Web API?

Web API and REST

• When you speak about Web API, probably you should know REST, but was does it mean?

• RESTfull= REpresentational State Transfer

RESTful what????

Web API and REST

It is not a WebService (SOAP), a pattern or a protocol, but is a style of software architecture for distributed

systems such as the World Wide Web

Web API and REST

ASP.NET Web API is a framework (FW 4.x) for processing data and returning data, typically in json or xml (RESTful services);

It seems like MVC but it isn't, if you need both, use both.

What is similar to MVC?• Released with NuGet;• Routing;• Controllers and Actions;• Filters;• ModelBindings;• Dependency Injection;

What is different from MVC?• Dispatching (based on http verbs);• Formatters;• Async everywhere;• Self hosted (no need for IIS);• Content negotiation;

• Everything is under System.Web.Http;

RESTful• Stateless architecture based on HTTP;• Each url is a resources (no transaction between two

requests);• Base on HTTP Verbs (GET, POST, PUT, DELETE);• The status of the response is based on HTTP Status code

(401, 200, 404 and so on);

DEMO

ROUTING

Attribute RoutingAllows you to override the default routing for a single action/controller;

/customers/1/orders/api/v1/products/api/v2/products

Good Article: http://bit.ly/1dwdc2D

GLOBAL ERROR HANDLING

Global error handling (the problem)

There’s no easy way in Web API to log or handle errors globally (prev v2.x);

I.E.:

• Exceptions thrown from controller constructors• Exceptions thrown from message handlers• Exceptions thrown during routing• Exceptions thrown during response content serialization

Good Article: http://bit.ly/1eiUvBB

Global error handling (the solution)

WEB API (2.x) provides two new user-replaceable services, IExceptionLogger and IExceptionHandler, to log and handle unhandled exceptions. The services are very similar, with two main differences:

Global error handling (the solution)

Global error handling (CatchBlock)

DOCUMENTATION

There is a specific endpoint to call

Help Page• “Automatic” API Documentation;• Based on MVC (all via nuget);• Template on top of Bootstrap• Support validation attributes;• Code comments;• Support complex types also for GET Methods (new);• Support for Enums;

Help Page (Document your code)

Help Page (Enable the XML output)

Help Page (Specify the documentation file)

Do you know postman?

CORS

CORS - Cross-Origin Resource Sharing - (the problem)By default it's not possible to make HTTP requests using Javascript from a source domain that is different from the called endpoint.

For example, this means that it's not possible to call the URL http://mysite.com/api/myrestendpoint from a domain http://yoursite.com

This limitation was introduced for security reasons: in fact, without this protection, malicious javascript code could get info from another site with the user noticing.

CORS (the problem)

CORS (the problem)

Ok, but sometimes we need to do this. How can we do that?

• JSONP is easy to use and it's supported by all browsers; the only problem is that the only HTTP VERB supported is GET, which has a limitation on the length of the string that can be passed as query parameter.

• Otherwise, if you need to send lot of information we can't use this way, so the soulution could be to "proxy" the request locally and forward the data server side or to use CORS.

CORS (the solution)

Basically CORS communication allow you to bypass the problem by defining some rules that makes the request more "secure".

Of course the first thing we need is a browser that supports CORS: fortunately all the latest browsers support it.

Anyway, we have to consider that, looking at the real world, there are several clients that are still using Internet Explorer 8 which, among other things, doesn't fully support CORS (IE8 has limited support for CORS).

CORS (the solution)

http://caniuse.com/cors

•Internet Explorer 10/11•Chrome (all versions)•Firefox 3.5+•Safari 4.x

CORS

CORS

CORS

CACHING

CACHING

• Did you know that HTTP supports caching?• Do we really need to use server side caching?• What do I need to do in my code?

Caching

How does it work?

The client will ask the server if it has an updated copy of the resource by sending some information about the cached resources it holds using a request header called ETag

If there are no updates, the server return 304 with an empty body, otherwise a 200 with the new data

Caching Source: http://bit.ly/1md3r0N

Cache Cow

It’s an open source library available on nuget (the source code is on github) that allows you to enable caching in you APIs;

Supports different providers to store the cache (memcache, ravendb, azure caching, Redis and so on);

Cache cow

THANKS

Ugo LattanziHead of Technologies @ Gaia

Microsoft MVP, MCP

Twitter: @imperugo

Blog (en): http://tostring.it

Blog (it): http://imperugo.tostring.it

E-mail: imperugo@gmail.com