ASP.NET Mvc 4 web api
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This document provides an overview of ASP.NET MVC 4 Web API. It discusses what an API is and why Web API is used. It covers key concepts like HTTP, REST, JSON. It describes features of Web API like routing, error handling, model validation, OData support, media formatters, and security. It also discusses using the HttpClient class and future plans.
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ASP.NET Mvc 4 web api
- 1. ASP.NET MVC 4 Web API Tiago Knoch – tiago.knoch@comtrade.com
- 2. Contents • What is an API? • Why ASP.NET MVC Web API? • HyperText Transfer Protocol • REST • JSON • Introduction to Web API • Routing Table • Error & Exception Handling • Model Validation • Odata Protocol • Media Formatters • Security • HTTPClient • What Else? • Road Map
- 3. What is an API? • An application programming interface (API) is a specification intended to be used as an interface by software components to communicate with each other. An API may include specifications for routines, data structures, object classes, and variables. • For the web this mean Web Services (SOAP + XML + WSDL) but in Web 2.0 we are moving away to REST Services (HTTP + XML/JSON) – Web API • Web APIs allow the combination of multiple services into new applications known as mashups.
- 4. • Common examples: – Facebook, Twitter, Amazon, LinkedIn... Source: http://blogs.mulesoft.org/cloud-apis-and-the-new-spaghetti-factory/
- 5. Why ASP.NET MVC Web Api? • Web Api – Defined in HTTP – Messages in Json/XML – RESTful – CRUD operations – Ready for Cloud
- 6. HyperText Transfer Protocol • The Hypertext Transfer Protocol (HTTP) is an application protocol for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web. • HTTP functions as a request-response protocol in the client-server computing model. A web browser, for example, may be the client and an application running on a computer hosting a web site may be the server. • The client submits an HTTP request message to the server. The server, which provides resources such as HTML files and other content, or performs other functions on behalf of the client, returns a response message to the client. The response contains completion status information about the request and may also contain requested content in its message body.
- 7. HTTP – Example GET GET / HTTP/1.1[CRLF] Host: www.google.rs[CRLF] User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:15.0) Gecko/20100101 Firefox/15.0.1[CRLF] Accept-Encoding: gzip[CRLF] Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8[CRLF] Accept-Language: en-us,en;q=0.5[CRLF] Status: HTTP/1.1 200 OK Content-Type: text/html Content-Length: 1354 Content: <HTML data>
- 8. HTTP – Example POST POST /somepage.php HTTP/1.1 Host: example.com Content-Type: application/x-www-form-urlencoded Content-Length: 19 name=tiago&surname=knoch Status: HTTP/1.1 404 Not Found
- 9. Rest - Representational State Transfer • REST is a style of software architecture for distributed systems such as the WWW, where, virtually in all cases, the HTTP protocol is used. • Uses CRUD actions (HTTP methods) CRUD Action HTTP Method Create Post Read Get Update Put Delete Delete • Each resource is represented by an global id (URI in HTTP) • The resources are conceptually separate from the representations that are returned to the client (JSON/XML) In many ways, the World Wide Web itself, based on HTTP, can be viewed as a REST-based architecture. Despite being simple, REST is fully-featured; there's basically nothing you can do in Web Services that can't be done with a RESTful architecture!
- 10. JSON • JSON, or JavaScript Object Notation, is a text-based open standard designed for human-readable data interchange. It is derived from the JavaScript scripting language for representing simple data structures and associative arrays, called objects. Despite its relationship to JavaScript, it is language-independent, with parsers available for many languages.
- 11. ASP.NET MVC Web API • MVC: Model -> View -> Controller • Create a Model • Create a controller
- 12. Routing Table • Route is defined, by default, as api/{controller}/{id} where action is defined by an HTTP method (in global.asax Application_Start method). HTTP Method URI Path Action GET /api/products GetAllProducts GET /api/products/id GetProductById GET /api/products/?category=category GetProductsByCategory POST /api/products PostProduct PUT /api/products/id PutProduct DELETE /api/products/id DeleteProduct
- 13. Routing Table The four main HTTP methods are mapped to CRUD operations: • GET retrieves the representation of the resource at a specified URI. GET should have no side effects on the server. • PUT updates a resource at a specified URI (idempotent). • POST creates a new resource. The server assigns the URI for the new object and returns this URI as part of the response message. • DELETE deletes a resource at a specified URI (idempotent).
- 14. Oi?! Time for some DEMO!
- 15. Error & Exception Handling • Response messages, errors and exceptions are translated to HTTP response status codes. • For example: – POST request should reply with HTTP status 201 (created). – DELETE request should reply with HTTP status 204 (no content). • But: – If a PUT/GET request is done with an invalid id, it should reply with HTTP status 404 (not found) – Or if a PUT request has an invalid model, it can reply with HTTP status 400 (bad request)
- 16. Error & Exception Handling • By default, all .NET exceptions are translated into and HTTP response with status code 500 (internal error). • It is possible to register Exception filters:
- 17. Model Validation • Like MVC, Web API supports Data Annotations (System.ComponentModel.DataAnnotations, .net 4.0). • If in your model there is a difference between 0 and not set, use nullable values.
- 18. Model Validation - Example
- 19. Model Validation – FilterAttribute Create a FilterAttribute Add it to Filters in Global.asax App_Start
- 20. Odata Protocol • http://www.odata.org/ • “The Open Data Protocol (OData) is a Web protocol for querying and updating data. OData does this by applying and building upon Web technologies such as HTTP, Atom Publishing Protocol (AtomPub) and JSON to provide access to information from a variety of applications, services, and stores.” • In Web API we want to do something like this: /api/products?$top=3&$orderby=Name /api/products/?$filter=substringof('a', Name) eq true /api/products/?$filter=Price gt 5 /api/products/?$filter=Price gt 1 and Category eq 'Hardware'
- 21. Odata Protocol • Change GET action method to return IQueryable<T> and to use Queryable attribute • Available as Nuget package (prerelease)! PM> Install-Package Microsoft.AspNet.WebApi.OData -Pre
- 22. DEMO!
- 23. Media Formatters • Web API only provides media formatters for JSON (using Json.NET library) and XML! • In HTTP, the format of message body is defined by the MIME type (media type): text/html, image/png, application/json, application/octet-stream • When the client sends an HTTP request, the Accept header tells the server wich media type it expects: Accept: text/html, application/json, application/xml; q=0.9, */*; q=0.01 • Web API uses media formatters to: – Read CLR objects from an HTTP message body (HTTP requests serializes to action methods parameters), – Write CLR objects to an HTTP message body (action methods returned objects serializes to HTTP replies) • You can create your own Media Formatter to serialize-deserialize your model types!
- 24. Media Formatters - Example Define which http media type is supported Define which types can be deserialized
- 25. Media Formatters - Example Deserialize type to stream Define formatter in global.asax App_Start
- 26. Security • Support for the [Authorize] Attribute (System.Web.Http.AuthorizeAttribute)...but it only checks UserPrincipal.Identity.IsAuthenticated (Forms authentication). • For more secure options you need to implement a custom filter: – Tokens (ex, Public/Private Keys) – Oauth (http://oauth.net/) – OpenID (http://openid.net/) – Forms Authentication (already supported by ASP.NET) – Basic Http Authentication (username/password encrypted ) – SSL • Amazon S3 REST API uses a custom HTTP scheme based on a keyed-HMAC (Hash Message Authentication Code) for authentication. • The Facebook/Twitter/Google API use OAuth for authentication and authorization.
- 27. Testing from a .NET client - HttpClient • HttpClient - Available in .NET 4.5 or NuGet package Microsoft.AspNet.WebApi.Client • Or use RestSharp (http://restsharp.org/)
- 28. What else? • Improved support for IoC containers • Create help pages (IApiExplorer service) • Web API Project Template in VS 2012 • Scaffold controllers from Entity Framework model (like MVC) • Easy integration with Azure
- 29. Road Map • MVC 4 was released in ASP.NET 4.5 with Visual Studio 2012 and .NET Framework 4.5. • Check out more at http://www.asp.net/web-api
Editor's Notes
- Currently around 7 thousand APIsImage – Most used APIs All-Time
- You can make a Web API not RESTful if you want!
- Content = Body
- When a web browser sends a POST request from a web form element, the default Internet media type is "application/x-www-form-urlencoded".[1] This is a format for encoding key-value pairs with possibly duplicate keys. Each key-value pair is separated by an '&' character, and each key is separated from its value by an '=' character. Keys and values are both escaped by replacing spaces with the '+' character and then using URL encoding on all other non-alphanumeric[2] characters. HTML form tag should contains method="post".
- Rest is abstract! It’s an architecture, not a protocol or framework. You can implement a REST architecture in web or desktop apps, in web services, in whatever you want.
- The JSON format is often used for serializing and transmitting structured data over a network connection. It is used primarily to transmit data between a server and web application, serving as an alternative to XML.Douglas Crockford was the first to specify and popularize the JSON format.[1]JSON was used at State Software, a company co-founded by Crockford, starting around 2001. The JSON.org website was launched in 2002. In December 2005, Yahoo! began offering some of its web services in JSON.[2]Google started offering JSON feeds for its GData web protocol in December 2006.[3]
- If a method throw NotImplementedException, this ExceptionFilter kicks in
- Package Manager Console
- Media formatter is defined during HTTP Content NegoiationContent Negotiation is composed of the following headers:Accept: which media types the client can acceptAccept-Charset: which character sets are acceptable (ex, UTF-8 or ISO 8859-1)Accept-Encoding: which content encodings are acceptable (ex, gzip)Accept-Language: which culture is acceptable (ex, en-us, sr-SP-Cyrl, pt-pt)
- This is an example for deserialization (Get, from server to http). The correspondent methods for serialization exist (CanReadType and WriteToStream)
- IoC = Inversion of controlIApiExplorer is a service that can get a complete runtime description of your web APIs.
- ASP.NET MVC 4 was released in 15th Aug 2012You can use ASP.NET MVC4 with VS 2010 and .NET 4 too!