service oriented architecture and windows communication

New England Code Camp IV: “Developer’s Gone Wild”

Service Oriented Architecture and Windows Communication Foundation (ne ́e Indigo)

Michael Stiefelco-author Application Development Using C# and .NET

[email protected]


Goals– Understand what is meant by a Service

Oriented Architecture (SOA).– Understand the relationship between a SOA

and a Web service.– Understand the basics of Windows

Communication Foundation (WCF)


Fundamental Principle

• Service Oriented Architecture (SOA) is driven by business needs, not technical advancements– Contrary to the view of many vendors

• SOA is about approaches and principles, not fixed technical approaches or patterns– Leads to fuzziness that makes technical types

and geeks unhappy and wary


Architecture

• Study of the principles of design, construction, and esthetics of buildings

• The profession of designing, constructing, and ornamenting buildings

• The structure and organization of a particular building or class of buildings

• The confusion for developers is that SOA is about the first definition not the last.


SOA is an Architectural Style

• Principles, esthetics vary over historical periods– Gothic, Greek, Bauhaus, Greek revival, Victorian

• Principles, esthetics vary over types of artifacts– Military architecture, naval architecture, software architecture

• SOA is about the principles and esthetics of constructing loosely coupled, reusable application-agnostic services within the modern business environment


Modern Business Environment• Business cannot afford to rebuild every

application from scratch• Consumer and business customers’ demands

change quickly over time• Businesses depend on vendors and suppliers• SOA is about developing and connecting to

loosely coupled, reusable application-agnostic business services, not just building an application that meets specific business functionality or goals such as ROI or cost effectiveness


Document Centered Processing• Exchange Documents/Messages,

– No access of remote objects– Contract: content, order of versioned documents and

messages– Can contain their own state

• Security travels with the Message• Services made compatible through policy• Transactions do not span long running services

with no guaranteed connection– Compensating transactions


What is a Service?

• Explicit boundaries for code and data• Connected through versioned messaging• Can be rewritten or redeployed

independently• Interaction through schema and contracts,

not implementation– Clients and Services can evolve separately


Policy

• Provides service constraints.– X.509 Certificates are required for

identification– Applicant must have certain net worth– Response time or service availability


Object Oriented Evolution• Reuse through Inheritance

– Fragile Base Class Problem– “Inheritance Breaks Encapsulation”

• Reuse through Interface and Composition– Design Patterns

• Reuse through Templates• Dynamic Interface, Behavior Reuse with

Contracts– Next step in black box reuse


Service vs. ObjectObjectsWell-understoodSingle Execution EnvironmentTypeAssume fast, transparent networkCompile /Link Time BindingLinkers and LoadersObject References / AddressesUsually at the BoundariesService Implementation

ServicesNot new, but not familiarHeterogeneous EnvironmentSchemaMight have long delaysLoose Coupling / MessagingExecution Time BindingAddressingSecurity ThroughoutModel Real World Processes


Trust Boundaries

• The major driving force for SOA is the need to effectively map IT infrastructure to changing business needs.– Integrating systems from different divisions of

the same company or different businesses• Interoperability drives SOA.• With different organizations, services must

cross trust boundaries.


Web Services and SOA

• Enabling technology for SOA:– Independent of execution environment – Provide a clear boundary between services.– Allow for loose coupling– Set of industry standards


Windows Communication Foundation

• Unified Programming Model– ASMX, WSE, MSMQ, Remoting, Enterprise

Services• WS-* specification support• REST, POX support• Programming Model

– Imperative, Declarative, Configuration


Caveat• September CTP code

– Beta 1 (outdated) docs– Update subset of Beta 1 samples

• Concepts• Implementation


Basic Concepts

• Host• Address• Binding• Contract• Endpoint = Address + Binding + Contract• Behavior• Channel


Service Consumer and Provider

Service Consumer Service Provider

Endpoint

Endpoint

Message

Host

Endpoint = Address + Binding + Contract


• Greeting Service Example


Host• Controls service providers lifetime

– Self Hosting, within a managed application• Console, Windows Forms, Windows Service

– IIS Hosting– Windows Activation Services (WAS)

• ServiceHost class


Contracts

• Define the programmatic format of the interaction between the client and server.– Service Contract and Data Contract

• work together as Data and Operations in a class– Message Contract

• XML Messaging


Service Types

• Typed– can be simple or class data types

• Untyped– Send and receive Message instances,

approximates SOAP message• Typed Message

– Custom message classes derived from Message


Service Contract

• Annotate Interface or Class, Operations– Analogous to WSDL portType

[ServiceContract][BindingRequirements(RequiredOrderedDelivery=true)]public interface IHotelReservation{

[ServiceOperation]bool IsRoomAvailable(string startDate, int numberDays);

}


Data Contracts• Map CLR types to XML Schema types[DataContract]public class Stock{

[DataMember] public string symbol;[DataMember] public decimal price;

}[Service Contract]public interface StockTrading{

[OperationContract] bool BuyStock(Stock stock, decimal bidPrice);}


• Loan Service Example


Message Contracts (Typed Message)[MessageContract]public class PurchaseOrder{

[MessageHeader] public string orderId;[MessageBody] public OrderItem item;

}

[ServiceContract]public interface IContract{

[OperationContract]void SendPurchaseOrder(PurchaseOrder message);

}


• AutoInfo Example


Pure Messaging

• Interact with SOAP Headers– See Action manipulation

• Create Body directly


• Dispatch Example


Diagnostics

• Trace SOAP Messages• Trace Service, Client transitions


• DispatchTracing Example


Message Exchange Patterns

• Built from asynchronous one-way message.– LoanService Example

• Synchronous Request / Reply– Other examples

• Duplex / Asynchronous Callback


• LoanServiceDuplex Example


Binding• Specify aspects of service that do not relate to

the capabilities of your service.– Example:

• Capability: given a stock symbol, provide a quote• Basic Profile Binding: HTTP, text encoding, only transport

security, no duplex messaging

• Change binding without affecting capabilities• Service Quality may require certain bindings (i.e.

encryption or transactions)


Bindings

• Transport• Encoding• Protocols• Semantics


Transports

• TCP• HTTP• MSMQ• Named Pipes• Custom


Encodings

• Text• Binary• Custom


Protocols

• WS*• .NET• REST• POX• Custom


Semantics

• Session• Duplex• Security• Transactions

– (ACID, not WS-Business Activity)• Queued Delivery• Reliable Messaging


• LoanServiceReliableMessagingExample


Binding Configuration

• Configuration Files• Requirements Specfied in Code

– [ServiceContract]– [BindingRequirements]


Endpoint Reference“A Web service endpoint is a (referenceable)

entity, processor, or resource to which Web service messages can be addressed. Endpoint references convey the information needed to address a Web service endpoint.”

Web Services Addressing 1.0 CoreW3C Candidate Recommendation 17 August 2005


ServiceEndpoint• Address (URI)• AddressProperties• Binding • Contract• Providers define Endpoint • Consumers target it


URI• http://rfc.net/rfc3986.html• ftp://ftp.is.co.za/rfc/rfc1808.txt• news:comp.infosystems.www.servers.unix• tel:+1-816-555-1212 telnet://192.0.2.16:80/ • urn:oasis:names:specification:docbook:dtd:xml:4.1.2


IIS Hosting Address• http://machine-name [:port][/vdirpath] filename.svc


Base Address

• Address can be specified relative to a base address:– “http://localhost/WeatherService/”– “”– “Temperature”

• A service can have multiple base addresses


Specify Address in Config File<endpoint

configurationName=“WeatherEndpoint”address = “http://localhost/WeatherService/service.svc”binding = “basicHTTPBinding”contract = “IWeather” />


Behaviors

• Service Internals– Concurrency– Instancing– Faults, Exceptions– Metadata customization– Instance Pooling– Impersonation, Protection, Authorization– AutoEnlist, Isolation, AutoComplete


Security• Message Exchange• Resource Access• Audit Resource Requests• Built-In

– Anonymous Credentials– X509 Certificates

• Sign with sender’s credentials• Encrypt with recipient's credentials

• Focus on Credentials, not Tokens• Extensible


Security Gates

• Host– File, Url Permissions

• Operation Contract / Message– Principal Permission

• Imperative (Code)– System.Security


Reliable Messaging

• Create Session, guarantee message delivery

[BindingRequirements(RequireOrderedDelivery = true)]


Programming• Metadata Exchange

– svcutil http://localhost/LoanService/service.svc/out:LoanProxy.cs /noConfig

– Can generate proxy, custom configuration


OperationContext.Current

• Host• IncomingMessageHeaders• InstanceContext• RequestContext• ServiceSecurityContext• SessionIdentifier• SupportingTokens


ServiceDescription• Metadata about Service• Behaviors

– Program Requirements, Instance mode, concurrency, transaction level, security

• Endpoints– Addresses to which services can be addressed

• Type– CLR type implementing the service

• Validators– Enforce Binding requirements


Summary

• WCF Unifies Microsoft Programming Model