building restfull data services with webapi
TRANSCRIPT
Building RESTfull Data Services with WebAPIGert Drapers (#DataDude)
Principle Software Design Engineer
Agenda
•Overview
•OData Core Libraries
•Web API
•Web API Demo
Overview
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
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
OData Status
• OData v4 to be standardized in Feb. in OASIS• http://docs.oasis-open.org/odata/new-in-odata/v4.0/cn01/new-in-odata-v4.0-
cn01.html
• ODL 6.2• http://blogs.msdn.com/b/odatateam/archive/2014/04/14/odl-6-2-release-
announcement.aspx
• Web API OData 6.1• http://blogs.msdn.com/b/odatateam/archive/2014/03/21/odata-6-1-and-odata-
client-6-1-are-now-shipped.aspx
• WCF Data Services moved to OSS• http://blogs.msdn.com/b/odatateam/archive/2014/03/27/future-direction-of-wcf-
data-services.aspx
http://odata.org/
OData Core Libraries
Technology BasicsClient 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
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 objectGet http://localhost:8080/OData/Accounts(110)Patch http://localhost:8080/OData/Accounts(110)
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
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.
EDM ExampleEntity Container
Entity set(Categories)
CategoryCategoryId Product
Entity set(Products)
ProductProductId Description
Navigation property binding
EDM Example – Cont.• <?xml version="1.0" encoding="utf-8"?>
<edmx:Edmx Version="4.0" xmlns:edmx="http://docs.oasis-open.org/odata/ns/edmx"><edmx:DataServices>
<Schema Namespace="Microsoft.Test.OData.Services.ODataWCFService" xmlns="http://docs.oasis-open.org/odata/ns/edm"><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>
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
OData Protocol Library• Deserialize/Serialize payload
• JSON• Full metadata level
– {– "@odata.context":"http://localhost:50671/ODataService.svc/OData/$metadata#Products/$entity",– "@odata.id":"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
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• $expand=: Returns the navigation property in an entity
URI Parser
OData Protocol Library – Cont.
• http://services.odata.org/V3/Northwind/Northwind.svc/Order_Details?$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
OData Web API
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
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 codevar builder = new ODataConventionModelBuilder();
builder.EntitySet<Product>("Products");IEdmModel model = builder.GetEdmModel();
•ODataController: VS2013 scaffolding
Web API OData Architecture Diagram
Message Handler
Controller Selection
ODataController
Action
Action Filter
MapODataRoute*GetEdmModelModel builderEdm Lib
Spatial Lib
Formatter
OData LibSerialize
DeserializeQuery
Entity Framework
DbContextDbSet
Action Filter
Formatter Model Binder QueryOption
Action Selection
Type system
HttpRequestMessage
HttpResponseMessage
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
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" }
);
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})/$links/{navigationProperty}");
Routing Examples…
// Routes for urls both producing and handling URLs// like: ~/Product(1), ~/Products() and ~/Products configuration.Routes.MapHttpRoute(
ODataRouteNames.GetById, "{controller}({id})");
configuration.Routes.MapHttpRoute(ODataRouteNames.DefaultWithParentheses, "{controller}()");
configuration.Routes.MapHttpRoute(ODataRouteNames.Default, "{controller}");
Model Builder
• ODataConventionModelBuilder• Use reflection and conventions to generate an Edm model
• Reflection• Type• PropertyInfo• MethodInfo
• Conventions• AttributeConvention• AttributeEdmTypeConvention: [DataContract]• AttributeEdmPropertyConvention:
• [Key]• [DataMember]• [IgnoreDataMember]• [Required]• [ConcurrencyCheck]…
ODataModelBuilder
• Take full controlvar builder = new ODataModelBuilder();var products = builder.EntitySet<Product>("Products");var product = products.EntityType;product.HasKey(p => p.ID);product.Property(p => p.Name);var rate = product.Action("Rate");rate.Parameter<int>("Rating");rate.Returns<double>();
• EntitySetConfiguration
• EntityTypeConfiguration
• PropertyConfiguration
• ProcedureConfiguration
• ParameterConfiguration
Query
• /Products/?$filter=Name eq ‘abc’• One key differentiator than other Web API implementations
• QueryableAttribute[Queryable]public IQueryable<Product> GetProducts(){
return db.Products;}
• => ODataQueryOptionspublic IEnumerable<Product> GetProducts(ODataQueryOptions options){
return options.ApplyTo(db.Products) as IEnumerable<Product>;}
• FilterQueryOption -> FilterBinder:• Convert OData AST FilterClause’s QueryNode to Linq Expression
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
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
DemoBuild an OData Web API application
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