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The Lightweight Approach to
» Fifth level
Building Web Based APIs with
.NET
MOW 2012
19-04-2012 1

2. Agenda
 Who Am I?
 What is “lightweight”
 RestBucks
 REST
 Nancy

3. What is lightweight?
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4. What is lightweight?
 Low ceremony
 Low cruft
 Conventions
4

5. What is lightweight?
 Open
 Agile
 Inexpensive
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6. Restbucks
6

7. REST
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8. REST – Richardsons Maturity Model
Level 3: Hypermedia
Level 2: HTTP Verbs
Level 1: Resources
Level 0: POX-RPC
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9. REST - Resources
 The basic building blocks of web API
 Anything with a URI
 http://restbucks.com/menu/
 http://restbucks.com/orders/
 http://restbucks.com/order/42/
 http://restbucks.com/order/42/payment/
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10. REST- Representations
GET http://restbucks.com/order/19202048/ HTTP/1.1
Accept: application/vnd.restbucks+xml
<?xml version="1.0"?>
<order xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="h
<links>
<link uri="http://restbucks.com/order/19202048" rel="http://restbucks
<link uri="http://restbucks.com/order/19202048" rel="http://restbucks
<link uri="http://restbucks.com/order/19202048" rel="http://restbucks
<link uri="http://restbucks.com/order/19202048/payment" rel="http://r
</links>
<location>inShop</location>
<cost>7.60000</cost>
<items>
<item>
<name>Latte</name>
<quantity>1</quantity>
<milk>skim</milk>
<size>large</size>
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</item>

11. REST - Representations
GET http://restbucks.com/order/19202048/ HTTP/1.1
Accept: application/vnd.restbucks+json
{
"Location":inShop,
"Cost":7.60000,
"Items":[
{
"Name":"Latte",
"Quantity":1,
"Preferences":{
"milk":"skim",
"size":"large"
}
}
],
"Status":1,
"Links":[
{
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"Uri":"http://restbucks.com/order/19202048",

12. REST - verbs
 GET
 POST
 PUT
 DELETE
 HEAD
 OPTIONS
 PATCH
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13. REST - Headers
 Accept
 Content-Type
 If-None-Match
 Etag
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14. 14

15. Why Nancy?
 “Close” to http
 Very, very readable code
 Very explicit routing
 Embraces modularity
 Embraces IoC/DI
 Embraces testing
 Runs anywhere
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16. Nancy Basics
 Organizes your routes
public class MainModule : NancyModule
{
public MainModule()
{
Get["/"] = _ => "Hello from root";
}
}
public class SubModule : NancyModule
{
public SubModule() : base("subpath")
{
Get["/"] = _ => "Hello from subpath";
}
}

17. Nancy Basics
 Defines which verbs you accepts
public class MainModule : NancyModule
{
public MainModule()
{
Get["/"] = _ => "Hello from root";
Post["/”] = _ => DoPost(Request.Form.my_value)
Delete["/{id}”] = p => Delete(p.id);
Put["/”] = _ => DoPut(Request.Body);
Patch["/”] = _ => DoPatch(Request.Body);
}
}
 HEAD and OPTIONS and automatic

18. Restbuck on Nancy – Place an Order
public OrdersResourceHandler(IRepository<Product> productRepository,
IRepository<Order> orderRepository) : base("/orders")
{
this.productRepository = productRepository;
this.orderRepository = orderRepository;
Post["/"] = _ => HandlePost(this.Bind<OrderRepresentation>());
}
private Response HandlePost(OrderRepresentation orderRepresentation)
{
var order = TryBuildOrder(orderRepresentation);
if (!order.IsValid())
return InvalidOrderResponse(order);
orderRepository.MakePersistent(order);
return Created(order);
}
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19. RestBucks on Nancy – View an Order
public OrderResourceHandler(IRepository<Order> orderRepository) : base(”/order”)
{
this.orderRepository = orderRepository;
Get["/{orderId}/”] = parameters => GetHandler((int) parameters.orderId);
…
}
public Response GetHandler(int orderId)
{
var order = orderRepository.GetById(orderId);
if (order == null)
return HttpStatusCode.NotFound;
if (order.Status == OrderStatus.Canceled)
return Response.MovedTo(new ResourceLinker(CanceledOrderUri(orderId);
if (Request.IsNotModified(order))
return Response.NotModified();
return Response.WithContent(Request.Headers.Accept,
OrderRepresentationMapper.Map(order,Request.BaseUri()))
.WithCacheHeaders(order);
}
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20. RestBucks on Nancy – Cancel an Order
Delete["/{orderId}/"] = parameters => Cancel((int) parameters.orderId);
public Response Cancel(int orderId)
{
var order = orderRepository.GetById(orderId);
if (order == null)
return HttpStatusCode.NotFound;
order.Cancel("canceled from the rest interface");
return HttpStatusCode.NoContent;
}
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21. RestBucks on Nancy –Pay an Order
Post["/{orderId}/payment"] = parameters => Pay((int) parameters.orderId,
this.Bind<PaymentRepresentation>());
public Response Pay(int orderId, PaymentRepresentation paymentArgs)
{
var order = orderRepository.GetById(orderId);
if (order == null)
return HttpStatusCode.NotFound;
order.Pay(paymentArgs.CardNumber, paymentArgs.CardOwner);
return HttpStatusCode.OK;
}
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22. RestBucks on Nancy – XML or JSON
return
Response.WithContent(Request.Headers.Accept,
OrderRepresentationMapper.Map(order, Request.BaseUri()))
.WithCacheHeaders(order);
public static Response WithContent<T>(this IResponseFormatter formatter,
IEnumerable<Tuple<string, decimal>> acceptHeaders,
T content)
{
var xmlWeight = CalculateWeightForContentType(acceptHeaders, "xml");
var jsonWeight = CalculateWeightForContentType(acceptHeaders, "json");
if (jsonWeight > xmlWeight)
return formatter.AsJson(content);
else
return formatter.AsXml(content);
}
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23. RestBucks on Nancy – Conditional Gets
return
Response.WithContent(Request.Headers.Accept,
OrderRepresentationMapper.Map(order, Request.BaseUri()))
.WithCacheHeaders(order);
public static Response WithCacheHeaders(this Response response,
IVersionable versionable,
TimeSpan? maxAge = null)
{
return
response.WithHeaders(
new { Header = "ETag",
Value = string.Format(""{0}"", versionable.Version) },
new { Header = "Cache-Control",
Value = string.Format("max-age={0}, public",
maxAge ?? TimeSpan.FromSeconds(10)) });
}
23

24. RestBucks on Nancy – Conditional Gets
if (Request.IsNotModified(order))
return Response.NotModified();
public static bool IsNotModified(this Request request, IVersionable versionable)
{
if (!request.Headers.IfNoneMatch.Any())
return false;
var etag = request.Headers.IfNoneMatch.First();
return string.Format(""{0}"", versionable.Version) == etag;
}
public static Response NotModified(this IResponseFormatter formatter,
TimeSpan? maxAge = null)
{
Response response = HttpStatusCode.NotModified;
return response.WithHeaders(
new { Header = "ReasonPhrase", Value = "Not modified"},
new { Header = "Cache-Control",
Value = string.Format("max-age={0}, public",
maxAge ?? TimeSpan.FromSeconds(10)) });
}
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25. Nancy.Hosting
Your Application
Nancy
Nancy.Hosting
…

26. Nancy.Hosting
 Usage:
 > Install-Package Nancy.Hosting.*
 Hosts:
 ASP.NET
 WCF
 Self
 OWIN

27. Nancy.Testing
[Test]
public void WhenOrderHasNotChanged_ThenReturn304()
{
// Arrange
var orderRepo = new RepositoryStub<Order>(new Order(1, 123);
var app = new Browser(
new ConfigurableBootstrapper
(with =>
{
with.Dependency<IRepository<Product>>(…);
with.Dependency<IRepository<Order>>(orderRepository);
}
));
// Act
var response =
app.Get("/order/123/",
with =>
{
with.HttpRequest();
with.Header("If-None-Match", ""1"");
});
//Assert
response.StatusCode.Should().Be.EqualTo(HttpStatusCode.NotModified);
29}

28. Why Nancy?
 “Close” to http
 Very, very readable code
 Very explicit routing
 Embraces modularity
 Embraces IoC/DI
 Embraces testing
 Runs anywhere
30

29. Why REST + Nancy
 Lightweight
 Low ceremony
 Low cruft
 Follows conventions
 Open
 Agile
31

30. More …
 Restbucks on Nancy: http://github.com/horsdal/Restbucks-on-Nancy
 Rest in Practice: http://restinpractice.com/book.html
 Nancy: www.nancyfx.org
 Me:
 Twitter: @chr_horsdal
 Blog: horsdal.blogspot.com
 email: chg@mjolner.dk
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