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Building RESTfull Data Services with WebAPI


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Data services are a major building block inside a service oriented architecture. Not only do they provide the abstraction and isolation between physical storage systems and the business layer, they can also provide the means for: authentication, authorization, transformation, projection, scale (through for example sharding) and caching. This session will walk you through implementing your RESTfull data service so that you can easily enable and integrate the described capabilities

Published in: Software, Technology

Building RESTfull Data Services with WebAPI

  1. 1. Building RESTfull Data Services with WebAPI Gert Drapers (#DataDude) Principle Software Design Engineer
  2. 2. Agenda •Overview •OData Core Libraries •Web API •Web API Demo
  3. 3. Overview
  4. 4. OData Value Proposition • Problem Statement: • There is no consistent data interoperability protocol for addressing and manipulating enterprise data across various devices and platforms • Value Proposition: • OData enables consistent REST-based data access from a variety of back ends including relational databases, file systems, content management systems, and traditional Web sites • OData builds on widely-accepted standards like HTTP, JSON, AtomPub, and URIs to address and access data
  5. 5. What OData Is and Is Not? • What OData Is: • Easy, consistent data access via HTTP endpoints • REST-based data operations: CRUD, Filtering, Sorting, Paging, Custom Operations, Delta, etc. • Service centric data definition, operation and annotation • Schematized and schema-less data sets • Broadly accepted JSON/ATOM format on the wire • What OData Is Not: • Not to replace native or direct data access interface, e.g. ODBC/TDS for SQL • Not to replace highly specialized BI technologies like XMLA
  6. 6. OData Status • OData v4 to be standardized in Feb. in OASIS • cn01.html • ODL 6.2 • announcement.aspx • Web API OData 6.1 • client-6-1-are-now-shipped.aspx • WCF Data Services moved to OSS • data-services.aspx
  7. 7. OData Core Libraries
  8. 8. Technology Basics Client Server OData Service OData Protocol Library OData Data Model Library Data Source Technology .NET OData Data Model Library Microsoft.odata.edm.dll OData Protocol Library Microsoft.odata.core.dll OData Service WCF Data Service/ Web API/ User’s own service OData Client Library Microsoft.odata.client.dll Code Generator T4 / item template OData Protocol Library OData Data Model Library OData Client Library OData Protocol Library OData Data Model Library
  9. 9. How to build client to consume OData Business Logic Dev OData Service Metadata request Use Code Generatror to generate client class Client Application Account account = TestClientContext.Accounts.Where(account => account.AccountID == 110).Single(); account.Country=”US”; TestClientContext.UpdateObject(account); TestClientContext.SaveChanges(); Code Files(Account.cs/ TestClientContext.cs) Microsoft.odata.client.dll The client dll will generate the request based on the property change on the Account object Get http://localhost:8080/OData/Accounts(110) Patch http://localhost:8080/OData/Accounts(110)
  10. 10. What’s in Microsoft.OData.Client.dll •Deserialize/Serialize OData payload • Using API provided by Microsoft.OData.Core.dll •Request Generator/LINQ to URL •Entity Tracker •Batch support
  11. 11. OData Data Model Library • OData is based on the Entity Data Model (EDM): • EDM presents information in a way which is familiar to many developers dealing with data today making it easy for them to understand and use. • Data provider can use OData Data Model Library to create the EDM model of the data they want to expose. The client can consume the data based on the EDM model that exposed by service and figure out the relationship between entities.
  12. 12. EDM Example Entity Container Entity set (Categories) Category CategoryId Product Entity set (Products) Product ProductId Description Navigation property binding
  13. 13. EDM Example – Cont. • <?xml version="1.0" encoding="utf-8"?> <edmx:Edmx Version="4.0" xmlns:edmx=""> <edmx:DataServices> <Schema Namespace="Microsoft.Test.OData.Services.ODataWCFService" xmlns=""> <EntityType Name="Category"> <Key> <PropertyRef Name="CategoryId" /> </Key> <Property Name="CategoryId" Type="Edm.String" Nullable="false" /> <Property Name="Name" Type="Edm.String" Nullable="false" /> <NavigationProperty Name="Product" Type="Microsoft.Test.OData.Services.ODataWCFService.Product" Nullable="false" /> </EntityType> <EntityType Name="Product"> <Key> <PropertyRef Name="ProductId" /> </Key> <Property Name="ProductId" Type="Edm.String" Nullable="false" /> <Property Name="Name" Type="Edm.String" Nullable="false" /> <Property Name="Desciption" Type="Edm.String" Nullable="false" /> </EntityType> <EntityContainer Name="ServiceContainer"> <EntitySet Name="Categories" EntityType="Microsoft.Test.OData.Services.ODataWCFService.Category"> <NavigationPropertyBinding Path="Product" Target="Products" /> </EntitySet> <EntitySet Name="Products" EntityType="Microsoft.Test.OData.Services.ODataWCFService.Product"> </EntitySet> </EntityContainer> </Schema> </edmx:DataServices> </edmx:Edmx>
  14. 14. EDM Example – Cont. • Category Entity: • http://localhost/odata/Categories(1) • Product under this category • http://localhost/odata/Categories(1)/Product • Through navigation binding defined in the Categories and the navigation property defined in the Category, target entity set Products can be found • Entity product can be located in entity set Products
  15. 15. OData Protocol Library • Deserialize/Serialize payload • JSON • Full metadata level – { – "@odata.context":"http://localhost:50671/ODataService.svc/OData/$metadata#Products/$entity", – "":"http://localhost:50671/ODataService.svc/OData/Products(5)", – "@odata.editLink":"http://localhost:50671/ODataService.svc/OData/Products(5)", – "ProductID":5, – "Name":"Cheetos", – "Description":"Cheese curl" – } • Minimal metadata level – Writer only writes the necessary metadata – Reader will auto complete the metadata during reading – { – "@odata.context":"http://localhost:50671/ODataService.svc/OData/$metadata#Products/$entity", – "ProductID":5, – "Name":"Cheetos", – "Description":"Cheese curl" – } • No metadata level – Data only – { – "ProductID":5, – "Name":"Cheetos", – "Description":"Cheese curl" – } • ATOM
  16. 16. OData Protocol Library • Targeting the target resource based on the URI • $top=n: Returns only the first n entities in an entity set (or in Atom terms, the first n entries in a feed) • $skip=n: Skips the first n entities in an entity set. Using this option lets a client retrieve a series of distinct pages on subsequent requests • $format: Determines whether data should be returned in JSON or the XML- based Atom/AtomPub format • $orderby=: Orders results, in ascending or descending order, by the value of one or more properties in those results • $filter=: Returns only entities that match the specified expression • $select=: Returns only the specified properties in an entity • $expand=: Returns the navigation property in an entity URI Parser
  17. 17. OData Protocol Library – Cont. •$top=5 &$select=OrderID,ProductID&$skip=1&$filter=OrderID gt 10248 • Parsed result of request URI as an ODataUri object • TopCount • SkipCount • SelectExpandClause • List<SelectedItem> – PathSelectionItem » Path=OrderID – PathSelectionItem » Path=ProductID • FilterClause • FilterExpression
  18. 18. OData Web API
  19. 19. WebApi.OData: Overview •An OData service library •Build upon a lightweight http stack •Be part of ASP.NET RESTful framework •Selective query ability •Another option to build OData service
  20. 20. Simple way to build OData Service •No need to know the details of OData Protocol •POCO (Plain Old CLR Object) model •ODataConventionModelBuilder: 3 lines of code var builder = new ODataConventionModelBuilder(); builder.EntitySet<Product>("Products"); IEdmModel model = builder.GetEdmModel(); •ODataController: VS2013 scaffolding
  21. 21. Web API OData Architecture Diagram Message Handler Controller Selection ODataController Action Action Filter MapODataRoute*GetEdmModelModel builderEdm Lib Spatial Lib Formatter OData Lib Serialize Deserialize Query Entity Framework DbContext DbSet Action Filter Formatter Model Binder QueryOption Action Selection Type system HttpRequestMessage HttpResponseMessage
  22. 22. Components • Model builder • ODataModelBuilder • ODataConventionModelBuilder (a 3 lines of code approach) • Query • ODL Semantic AST -> LINQ Expression (IQueryable) -> LINQ to * (Entities, Objects…) • Routing • Conventional • Attribute route • Formatter • Serializer: CLR type / typeless -> OData*Value • Deserializer: OData*Value -> CLR type / typeless
  23. 23. Routing Examples // Metadata routes to support $metadata and code generation in the // WCF Data Service client. configuration.Routes.MapHttpRoute( ODataRouteNames.Metadata, "$metadata", new { Controller = "ODataMetadata", Action = "GetMetadata" } ); configuration.Routes.MapHttpRoute( ODataRouteNames.ServiceDocument, "", new { Controller = "ODataMetadata", Action = "GetServiceDocument" } );
  24. 24. Routing Examples… // Relationship routes (notice the parameters is {type}Id not id, // this avoids colliding with GetById(id)). // This code handles requests like ~/ProductFamilies(1)/Products configuration.Routes.MapHttpRoute( ODataRouteNames.PropertyNavigation, "{controller}({parentId})/{navigationProperty}"); // Route for manipulating links, the code allows people to create and // delete relationships between entities configuration.Routes.MapHttpRoute( ODataRouteNames.Link, "{controller}({id})/$links/{navigationProperty}");
  25. 25. Routing Examples… // Routes for urls both producing and handling URLs // like: ~/Product(1), ~/Products() and ~/Products configuration.Routes.MapHttpRoute( ODataRouteNames.GetById, "{controller}({id})"); configuration.Routes.MapHttpRoute( ODataRouteNames.DefaultWithParentheses, "{controller}()"); configuration.Routes.MapHttpRoute( ODataRouteNames.Default, "{controller}");
  26. 26. Model Builder • ODataConventionModelBuilder • Use reflection and conventions to generate an Edm model • Reflection • Type • PropertyInfo • MethodInfo • Conventions • AttributeConvention • AttributeEdmTypeConvention: [DataContract] • AttributeEdmPropertyConvention: • [Key] • [DataMember] • [IgnoreDataMember] • [Required] • [ConcurrencyCheck]…
  27. 27. ODataModelBuilder • Take full control var builder = new ODataModelBuilder(); var products = builder.EntitySet<Product>("Products"); var product = products.EntityType; product.HasKey(p => p.ID); product.Property(p => p.Name); var rate = product.Action("Rate"); rate.Parameter<int>("Rating"); rate.Returns<double>(); • EntitySetConfiguration • EntityTypeConfiguration • PropertyConfiguration • ProcedureConfiguration • ParameterConfiguration
  28. 28. Query • /Products/?$filter=Name eq ‘abc’ • One key differentiator than other Web API implementations • QueryableAttribute [Queryable] public IQueryable<Product> GetProducts() { return db.Products; } • => ODataQueryOptions public IEnumerable<Product> GetProducts(ODataQueryOptions options) { return options.ApplyTo(db.Products) as IEnumerable<Product>; } • FilterQueryOption -> FilterBinder: • Convert OData AST FilterClause’s QueryNode to Linq Expression
  29. 29. Routing • IODataRoutingConvention • string SelectController(ODataPath odataPath, HttpRequestMessage request); • string SelectAction(ODataPath odataPath, HttpControllerContext controllerContext, ILookup<string, HttpActionDescriptor> actionMap); • Convention based route: • EntitySetRoutingConvention • EntityRoutingConvention • ActionRoutingConvention • FunctionRoutingConvention • NavigationRoutingConvention • PropertyRoutingConvention • Attribute based route: • AttributeRoutingConvention • ODataRouteAttribute • MapODataRoute
  30. 30. Formatter • Why does webapi.odata need to handle serialization and deserialization? • ODL handles OData object model to Payload • Web API handles POCO to OData OM • The hook: [ODataFormatting] public abstract class ODataController : ApiController • ODataFormattingAttribute • Inserts the ODataMediaTypeFormatters into the HttpControllerSettings.Formatters collection. • Attaches the request to the OData formatter instance. • ODataMediaTypeFormatter.Create() • ODataSerializerProvider / ODataDeserializerProvider • OData*Serializer / OData*Deserializer
  31. 31. Demo Build an OData Web API application
  32. 32. Laat ons weten wat u vindt van deze sessie! Vul de evaluatie in via en maak kans op een van de 20 prijzen*. Prijswinnaars worden bekend gemaakt via Twitter (#TechDaysNL). Gebruik hiervoor de code op uw badge. Let us know how you feel about this session! Give your feedback via and possibly win one of the 20 prices*. Winners will be announced via Twitter (#TechDaysNL). Use your personal code on your badge. * Over de uitslag kan niet worden gecorrespondeerd, prijzen zijn voorbeelden – All results are final, prices are examples